essay on waste water story

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Waste Water Story

1. WATER, OUR LIFELINE I. Water Water is an essential element in daily life. Water is used by all living organisms on earth to perform their life processes. Contaminants are the suspended and dissolved impurities of water. Humans contaminate water by their activities. Drinking contaminated water results in the development of diseases such as cholera, typhoid and arrowhead. Polluted water can sometimes be fatal. Water should be boiled and filtered before it is used for drinking as it contains many impurities that are not visible to naked eye. II. Wastewater Wastewater is the contaminated water which is often referred to as liquid waste. Liquid waste is mainly released from washrooms, kitchen and other areas where sewage gets collected. Liquid wastes are usually disposed of through closed drains. III. Components of waste water There are many components of waste water.

•  Sewage or liquid waste makes up the main component of waste water.

•  Human excreta in the form of faeces is the main suspended impurity in the sewage.

•  Oil and grease float as layers or froth on the waste water.

•  Industrial liquid wastes are the effluents contaminating water.

•  Agricultural wastes like pesticides, fertilisers do not dissolve in water but remain in the waste water.

IV. Causes for contamination of water

•  Human activities like bathing and washing clothes in rivers and lakes.

•  Animals bathing in rivers and lakes.

•  Increase in population forms the major cause for water contamination.

•  Untreated sewage.

•  Industrial wastes.

•  Agricultural wastes.

V. Water scarcity Water scarcity refers to lack of sufficient access to drinking water. Water has become so scarce that many people have to travel several kilometres to fetch drinking water. More than 1.5 billion people all over the world do not get clean drinking water. March 22nd is celebrated as World Water Day. It was on March 22, 2005, that the United Nations declared 2005-2015 as the International Decade for the Action “Water for Life”. Every house releases lot of waste water daily. Wastewater should be cleaned before it is drained into water bodies.

I. Sewage Sewage is liquid waste containing dissolved impurities called as contaminants. Contaminants are the harmful substances which can cause illness. Sewage comprises dissolved and suspended impurities.

•  Organic and inorganic impurities: Organic impurities in sewage include animal waste, urine, oil, vegetable and fruit waste, faeces, pesticides and herbicides. Inorganic impurities include phosphates, nitrates and metals.

•  Disease-causing bacteria:  Coliform bacteria and certain Bacilli.

•  Saprotrophic bacteria: Bacteria that feed on dead organisms.

•  Nutrients:  Sewage contains some useful nutrients, such as phosphorus and nitrogen.

•  Other microbes: Microbes that cause typhoid, cholera, diarrhoea and dysentery are present in sewage.

II. Types of Sewage

There are various types of sewage, depending upon the colour and odour.

•  Sullage water: Wastewater released from the kitchen is called sullage water. The contaminants in sullage water are mild detergents, oils and food particles.

•  Foul waste: Wastewater released from toilets is termed as foul waste. It consists of human waste and a lot of bacteria that release gases and bad odour. It is highly infectious.

•  Trade waste: Wastes released from industries and commercial organisations is called as trade waste. It consists of acids and strong chemicals that are toxic in nature.

•  Agricultural waste: Rain water which runs off from agricultural field carries toxic substances into water resources.

III. Sewerage Small and big pipes that carry waste water are called sewers. All sewers together form the sewerage. Wastewater is carried from home to the point of disposal, that is, the waste water treatment plant through sewerage. After the treatment of waste water, the clean water is released into nearby water bodies. Sewerage has manholes that can be used to clear blockages. Manholes are located at every 50 to 60 metres in the sewerage. Manholes are placed at every junction of pipes forming sewerage. In the absence of sewerage facility, waste water is directly drained into nearby streams and lakes resulting in water contamination.

3. WASTEWATER TREATMENT PLANT (WWTP) Wastewater needs to be treated before it can be reused or released into a water body. Wastewater Water treatment removes impurities from waste water. Wastewater from households is treated at a treatment plant to remove the physical, biological and chemical matter. Treatment of waste water reduces the toxicity of poisonous substances and pollutants in water resources.

I. Process of water treatment Sewage comprises of waste water released from homes, industries, hospitals and offices and also the water collected during rains. Sewage treatment is the step wise procedure which involves removal of wastes from the water. Sewage treatment is also called as waste water treatment.

II. Laboratory process of water treatment This involves filtration of water to remove large impurities. An activity is explained to show physical treatment of water.

•  Take a funnel.

•  Place a cone made up of filter paper in the funnel and wet it with water.

•  Add some sand, fine gravel and medium gravel into the funnel. These form the layers for the process of filtration of water.

•  Pour waste water into the funnel and collect clean water from the stem of the funnel.

•  Process has to be repeated for several times till the collected water looks clean.

III. Wastewater Treatment Plants (WWTP) Wastewater treatment involves physical, chemical and biological treatment of water. Wastewater is allowed to pass through different steps in a sequence.  Physical and biological treatment of waste water:

•  Step 1 – Bar Screens: Bar screens are the screens that prevent the flow of large objects in waste water. These screens help to remove large objects like rags, plastic bags, cans, napkins and sticks from sewage.

•  Step 2 – Grit chamber: Wastewater from the bar screens is allowed to pass through grit chambers in a slow manner. The slow movement of water makes grit, sand and dust particles to settle down.

•  Step 3 – Clarifier: A clarifier is a tank with its central part inclined downwards so as to allow faces to settle down. The waste settled at the bottom is termed as sludge. Sludge is transferred to a separate tank where it is decomposed using bacteria. Finally, a skimmer is used to remove oils and grease. Clarified water is obtained after the separation of all physical contaminants from the sewage.

•  Step 4 – Aerator :

The clarified water is passed into an aerator. An aerator pumps air into the water to settle the bacteria to the bottom of the tank as activated sludge. Bacteria under aerated conditions consume impurities left in the water. The water present in the top is 95% clean and is let out into a water source while the activated sludge is dried in a sand bed and is used as manure.

Using bacteria in decomposing waste is the biological treatment.       

Chemical treatment of waste water:

•  Chlorine tablets or chlorine gas is used to treat waste water chemically.

•  Water will be clean on the dissolution of a chlorine tablet. Hence, chlorine tablets are used to disinfect water in treatment plants.

•  Chlorine gas is introduced through many pipes into a tank with water stored after physical and biological treatment.

•  Ozone is also used in chemical purification of water.

IV. Water treatment in olden days

The ancient Greek and Indian writings dating back to as early as 2000 BC recommended water treatment methods. The Egyptians discovered the process of coagulation for water treatment. Eucalyptus trees are planted along the sewage ponds into which water is released. Eucalyptus trees absorbed waste water from the pond and released pure water vapour into the atmosphere .

V.  Prevention of clogging of drains

•  Oils and fats released from the kitchen can harden along with detergents to block water pipes. In an open drain, fats on entering the soil, clog the soil pores. This reduces the effectiveness of filtration of water or water seeping.

•  We should avoid throwing tea leaves, solid food remains and napkins into the drain. These can block the drains and also block the flow of oxygen to the useful microorganisms. Useful microorganisms bring about decomposition of organic wastes from waste water.

Chemicals like paints, medicines, motor oil and many other solvents kill the microbes that help in water treatment. Awareness has to be created in people about the ill effects of throwing pollutants into the drain.

4. BETTER HOUSE KEEPING PRACTICES Do not throw cooking oil and fat in the drain. This can block the drain. The fat and oil clogs the pores in the soil; in open drains. This reduces the filtering capacity of soil. Do not throw chemicals; like paint, insecticides, medicines, etc. into the drain. They kill the bacteria which otherwise help in cleaning the water. Do not throw used tea leaves, solid food, soft toys or napkins in the drain. They can clog the drain and do not allow oxygen to enter the sewage water. Oxygen is important for the natural process of decomposition.

5. SANITATION AND DISEASE I. Sanitation Sanitation refers to hygiene. Sanitation generally refers to the provision of facilities for the safe disposal of human urine and faeces.

•  The main objective of human health is to protect and provide clean environment.

•  Sanitation is a major problem in developing countries such as India and China.

•  Due to explosion in population, government is unable to provide proper sanitation through underground drainage system.

II.  Effects of poor sanitation Water and soil are polluted by open defecation. Contaminated water and soil prove to be breeding grounds for microorganisms. Poor sanitation contaminates the ground water which further causes diseases like cholera, typhoid, polio, meningitis, hepatitis and dysentery. Foul smell from open drains causes inconvenience and respiratory disorders in human beings.

6. SEWAGE DISPOSAL SYSTEMS On-site sewage disposal systems are the systems which collect human excreta and store it in a hole or a pipe and later directed into a sewage treatment plant. Other methods for sewage disposal are septic tanks, chemical toilets, composting pits and vermi-composting toilets. These on-site sewage disposal systems are cost-effective. a. Septic tanks Septic tank is a water tight chamber made of brick, concrete or glass. Solid particles settle down at the bottom and are degraded anaerobically. Effluent escapes through sewers and should be allowed to soak or evaporate. Advantages: Septic tanks are suitable for places such as hospitals, isolated buildings and cluster of houses where there is no sewerage. The septic tank system consists of a small sewage treatment system. Disadvantages: They require lot of space. They are costly to set up. They have to be periodically cleaned. Water seeps through the ground affecting trees and swimming pools b. Chemical toilets Aeroplanes and trains usually have chemical toilets. A chemical toilet uses chemicals to disinfect human waste and remove its bad odour. Advantages: These are portable latrines that could be set up anywhere. They do not require water. They control emission of foul odour. Disadvantages: They use toxic chemicals which are not advisable. These are costly. These are for temporary situations. c. Composting toilets A composting toilet is a system that converts human waste into organic compost and usable soil. This happens when micro-organisms such as bacteria and fungi, and macro-organisms such as earthworms oxidise organic waste to break it down into essential minerals. Advantages: These are more environmental- friendly. They require less water. They are well suited for village areas. Disadvantages: They require proper maintenance. They end up in emitting foul smell, encourage breeding of insects and increase health hazards. End products should be removed at periodic intervals. The rate of decomposition is very slow.

d. Vermi-Composting toilets A vermi-composting toilet is a process that involves earthworms which treat human excreta. The entire human waste is converted into vermi-compost. e. Sulabh toilets Organisations such as Sulabh International have developed a twin-pit pour flush toilet system that is being used by ten million people every day. The waste from these toilets flows through covered drains into a biogas plant for the generation of biogas and bio-fertilisers. Biogas plants offer safe and hygienic disposal of wastes. Advantages: Sulabh toilets are designed to suit the household conditions. They are affordable at price. They require less space. They eliminate mosquito breeding. They do not pollute the ground water. They are free from foul smell. They are easy to clean and maintain. Disadvantages: Though easy to maintain, they should be maintained properly. It needs attention of government or private agencies.

Litter and waste Litter and waste cause sanitation havoc at public places. This becomes common when exhibitions and fares are conducted. Public places such as railway stations, bus depots, airports and hospitals generate lot of waste, which leads to diseases. To prevent the breaking up of diseases, certain measures are to be taken and awareness among people should be created.

7.  SANITATION AT PUBLIC PLACES

Maintaining sanitation at public places is also important. In a heavily populated country; like India; any public place is always teeming with people. More footfall at public places results in more filth. Sanitation workers often work continuously to maintain cleanliness at public places. But it is our responsibility also to maintain sanitation at public places. We should follow some simple rules to help the sanitation workers. For example; always throw the trash in a dustbin and avoid littering. Don’t spit at public places and use the dustbin or special bins marked for the purpose.

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Wastewater Story for Class 7 Science Chapter 18: Notes

Wastewater Story:  We all know that water is the elixir of life and that access to clean water is one of our fundamental human rights, but did you realise that this right is routinely violated in India, with around \(63\) million people lacking access to safe drinking water? There is a water crisis in every corner of India, from rural villages to teeming megacities.

The water crisis is not only engrossing India; it is also enthralling superpower countries. People all across the world are battling to get the water they need for drinking, cooking, bathing, handwashing, and growing food both in quantity and quality. Let us take a close look at this situation and ways to address it.

Wastewater Story

Water is our lifeline because all living organisms use it on Earth to perform their life processes. It is the fundamental component that bathes us and feeds us. It is essential for all dimensions of life. With two-thirds of the earth’s surface covered by water and comprising \(75\) per cent of the human body, it is clear that water is one of the prime elements responsible for life on Earth. Without water, life on Earth would not evolve.

Agriculture is the primary food source for us, and water is the prime requirement for raising food crops. The existence of fishes which make up a large chunk of our food, depends on water. Forests that keep our ecological balance intact and provide us with numerous things also need water. It is a renewable, pollution-source of energy and the cheapest resource for generating hydroelectricity.

However, this ultimate resource of the earth has become an indispensable site for the disposal of urban Sewage and dirt. It is necessary not only to conserve water but also to purify used water before dumping it into seas or other bodies of water. As a result, the United Nations designated the years \(2005\) to \(2015\) as the International Decade for Action on ‘Water for Life.’

What is Wastewater?

Wastewater is the used or polluted water generated from rainwater runoff and human activities. It is full of impurities and cannot be reused. It is also called Sewage, typically categorized by how it is generated—specifically, as domestic Sewage, industrial Sewage, or storm sewage (stormwater).

Water Pollution

Water pollution is defined as the contamination or the addition of pollutants to the water present on the earth in the oceans, seas, rivers, lakes, and ponds. These pollutants may be toxic chemicals and biological agents that exceed what is naturally found in the water and pose a severe threat to humans and the environment.

The contamination of water results in a change in water’s physical, biological, and chemical properties, making it unsafe for drinking or domestic purposes. The substances or biological agents that cause water pollution are called Water Pollutants. The pollution of water has severe effects on health, the ecosystem of a region, and aquatic life.

Some of the major Water pollutants are:

• Sewage:  Sewage is a type of wastewater produced by a community of people. It contains wastewater from households and industries. When dumped in water bodies such as rivers and seas, it pollutes it and makes it unfit for any kind of consumption. It mainly consists of faeces, urine and laundry waste. These pollutants cause a rise in several bacteria and microorganisms that disrupt aquatic life and affects human health by causing diseases like cholera, diarrhoea, and typhoid.
• Industrial Chemical Wastes:  Potentially harmful contaminants—from arsenic to copper to lead and toxic chemicals are often dumped into water bodies contaminating the water directly.
• Agricultural Effluents:  The agricultural sector is the biggest consumer of global freshwater resources and a severe water polluter. Every time it rains, fertilizers, pesticides, and animal waste from farms and livestock operations wash nutrients and pathogens—such as bacteria and viruses—into our waterways. Nutrients such as nitrogen and phosphorus degrade water quality worldwide and lead to algal blooms.
• Oil Spills:  Accidents and leakages of tankers lead to oil spillage in the sea. This dramatically affects marine life. Oil causes blockages in the respiratory system and leads to the loss of aquatic life.
• Thermal Wastes:  Warm water from thermal industries often spilt in the water bodies leading to a rise in the temperature of the water body, which is not suitable for aquatic animals. Hence, it causes the loss of aquatic life.

What is Sewage?

Any liquid waste is called Sewage. The wastewater from houses, offices, industries, hospitals and other sources all forms of Sewage. Rainwater that flows into the drains during heavy rainfalls also forms Sewage because it contains pollutants that wash off the roads. The contaminants present in sewage water are:

A network of large and small pipes that carry sewage water is known as Sewerage, and the individual pipes through which Sewage flows is known as sewers.

The process in which contaminants or pollutants present in Sewage are removed from it before it reaches a water body or before it is used again is known as Sewage Treatment.

Wastewater Treatment Plant (WWTP)

We know wastewater is used water that includes substances such as food scraps, human waste, oils, soaps and chemicals. It also includes water from sinks, toilets, showers, bathtubs, dishwashers and washing machines. Industries and businesses also contribute their share of used water that must be cleaned before being dumped into water bodies.

Nature can cope with small amounts of water waste and pollution. However, it would be burdening and overwhelming if we didn’t treat the billions of gallons of wastewater we produce every day before releasing it back into the environment. Pollutants in wastewater are reduced to a level that nature can tolerate in treatment plants.

The fundamental goal of wastewater treatment is to remove as many suspended solids as possible before returning the leftover water, known as effluent, to the environment. Treatment of wastewater includes physical, chemical and biological processes of removal of the contaminants.

The physical and biological process of treatment of water:

1. Separation of Large Objects from Sewage Water

The wastewater is first made to pass through bar screens which remove big objects from the water like napkins, plastic bottles, cans, rags and sticks.

2. Separation of Sand and Dirt

The wastewater from the bar screens is sent to a grit and sand removal tank. The speed of the water is kept low to allow the sand, pebbles and dirt to settle down.

3. Removal of Solids

The water from the grit and sand removal tank cycles in a tank called Clarifier, which is sloped at the centre.

Solids like faeces settle at the bottom of the tank to form Sludge that is separated from the water with the help of a scrapper.

Floatable substances like oil and grease are removed with the help of a Skimmer to obtain clarified water.

The Sludge so obtained is transferred to a separate tank where the anaerobic bacteria decompose it. Biogas is produced in this process that can be used as fuel or can be used to produce electricity.

4. Suspended Sludge Removal

The clarified water obtained after removing the Sludge is moved to an aerator that pumps air into it. This process is called aeration. In this process, air allows aerobic bacteria to grow faster in the water.

The clarified water consists of organic waste, food waste, soaps and other elements. Aerobic bacteria decompose these wastes present in the clarified water.

This water is allowed to settle for several hours for these waste materials to settle down in the tank. This is called Activated Sludge.

After the solid has settled in the tank, the water is removed from the top of the activated Sludge with the help of machines or sand-drying beds. The dried Sludge can be further used as manure.

This treated water contains suspended matter and fewer amounts of impurities. The water so obtained can be safely dumped in a water body or under the ground. It is then discharged into rivers, seas or underground and left for nature to clean up.

Chemical Treatment of Wastewater

Sometimes disinfection of the treated water needs to be done even after treating them physically and biologically. Disinfectants such as chlorine and Ozone are used to remove harmful chemicals from the treated water.

Eucalyptus Plant and Cleaning of Water

Eucalyptus plants are planted along with the sewage ponds. This is because Eucalyptus plants absorb wastewater rapidly and release pure water vapour into the atmosphere. Hence, they act as a natural water purifier.

Better Housekeeping Practices

The best way to address the issue of sewage water is to check what is being released in the drains. Proper disposal of waste is essential to reduce sewage accumulation. Some housekeeping practices are:

• Oils and fats should never be put into sinks. This is because oil and fats harden and clog drains. Moreover, it isn’t easy to separate them from water.
• Chemicals like insecticides, pesticides, medicines and paints should not be drained off. They can kill the microbes in the water that help in its purification.
• A dustbin should be used to dispose of tea leaves, cotton, food remains, soft toys etc. These substances block pipes and clog drains.

Sanitation and Disease

A large number of people in low and middle-income countries die due to inadequate access to sanitation, water and hygiene each year, representing \(60\% \) of total diarrhoeal deaths. Out of these, around \(43200\) of these deaths is due to poor sanitation.

Better sanitation, water, and hygiene can prevent the deaths of children aged under five years each year.

Unsafe hygiene practices are widespread, compounding the effects on people’s health. Open defecation should be discouraged, and people should be encouraged to use toilets. Exposed faecal matter enters into the food chain and water resources, helping to spread serious diseases such as cholera. The lack of adequate sewerage or waste disposal systems can contaminate ecosystems and contribute to disease pandemics.

Benefits of Improving Sanitation

Improved sanitation extends beyond reducing the risk of diarrhoea. These include:

• reducing the spread of intestinal worms and the impact of malnutrition;
• promoting dignity and boosting safety, particularly among women and girls;
• promoting school attendance: girls’ school attendance is mainly boosted by the provision of separate sanitary facilities; and
• potential recovery of water, renewable energy and nutrients from faecal waste.

Alternative Arrangement for Sewage Disposal

Onsite sewage disposal methods such as septic tanks, compost pit toilets and chemical toilets are being used nowadays. The onsite sewage treatments treat and dispose of the wastewater or sewage using natural techniques.

• Septic Tanks – Septic tanks are commonly constructed underground in houses or buildings to allow anaerobic microorganisms to decompose sewage from the household.
• Chemical Toilets – A chemical toilet is a toilet with a separate chamber that uses chemicals to treat human waste and minimise odour.
• Composting Toilets – A composting toilet uses aerobic bacteria in a storage tank to treat human waste. These bacteria digest garbage and convert it to compost.

Access to safe drinking water is a prerequisite for development. People are better able to practise good hygiene and sanitation when they have access to clean water. The most vulnerable to diseases caused by contaminated water are women and children.

Unfortunately, this elixir of life is being butchered at the hands of the most intelligent creations of God. Instead of conserving water, we are wasting it.

It’s high time that we educate the general public about the significance of recycling, storing and reusing water, or else clean water is destined to become one of the rarest commodities soon.

FAQs on Wastewater Story

Let’s look at some of the commonly asked questions about wastewater stories:

Q.1. What are the possible origins of wastewater? Ans: The possible origins of wastewater are from homes that comprise domestic Sewage, from industries that make up industrial sewage and storm sewage.

Q.2. What happens to the wastewater after being released from the treatment plants? Ans: The treated wastewater is released into local waterbodies. It is used again for many purposes, such as supplying drinking water, irrigating crops, and sustaining aquatic life.

Q.3. What is removed from wastewater? Ans: Organic, inorganic and suspended solids are removed from wastewater after being treated at wastewater treatment plants. Harmful bacteria and pathogens, including chemicals, are removed by using certain disinfectants such as chlorine and Ozone.

Q.4. What is the difference between wastewater and Sewage? Ans: The terms’ wastewater’ and ‘sewage’ are used interchangeably. However, the prime difference is that ‘sewage’ is considered to be a subset of wastewater.

Q.5. Why is wastewater more expensive? Ans: The wastewater we produce may go back to water bodies and cause great damage to our ecosystem. Therefore, it is necessary to treat used water before releasing it to a water body. However, the treatment of effluent is not simple and costs money more than the treatment of drinking water.

Study Sources of Water Here

We hope this article on the wastewater story is helpful to you. If you have any queries about this page or in general about the wastewater story, reach us through the comment box below and we will get back to you as soon as possible.

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Home — Essay Samples — Environment — Water Conservation — Importance of Water Conservation

Importance of Water Conservation

• Categories: Water Conservation

About this sample

Words: 880 |

Published: Jan 30, 2024

Words: 880 | Pages: 2 | 5 min read

Table of contents

Introduction, the significance of saving water, methods of saving water, case studies/examples, challenges in water conservation and protection efforts, a. water conservation practices at homes.

• Installing water-saving fixtures and appliances, such as low-flow showerheads, faucets, and toilets.
• Fixing leaks and reducing water wastage by taking shorter showers, turning off the tap while brushing, and fixing dripping taps.
• Implementing efficient water usage habits such as using a broom instead of a hose to clean outdoor areas and washing laundry and dishes only with full loads.

B. Agriculture Water Management

• Implementing efficient irrigation techniques such as drip irrigation and precision irrigation, which reduce water wastage by up to 30%.
• Crop selection and rotation to optimize water usage by selecting crops that require less water and reducing water-intensive crops, such as rice and cotton.
• Using precision farming methods such as soil moisture sensors, weather forecasts, and crop modeling to optimize water usage.

C. Industrial Water Conservation

• Recycling and reusing water in manufacturing processes by using closed-loop systems.
• Implementing water-efficient technologies such as water-efficient boilers, cooling towers, and dry lubrication processes.
• Promoting water stewardship among industries by adopting best practices and engaging in water conservation efforts.

D. Government Policies and Programs

• Providing incentives for water-saving practices such as tax credits, rebates, and grants for installing water-efficient appliances and fixtures.
• Implementing water regulations and enforceable laws such as water pricing, water rights, and zoning regulations to ensure efficient water use.
• Educating and creating awareness among citizens through campaigns such as the WaterSense program, which educates consumers on water-efficient products.
• United Nations. (2021, March 22). Water and Sanitation. https://www.un.org/en/sections/issues-depth/water-and-sanitation/
• WaterSense. (n.d.). Water-Efficient Products. https://www.epa.gov/watersense/water-efficient-products
• Valsecchi, G. B., & Faggian, R. (2019). The Alliance for Water Stewardship certification program in the Netherlands: measuring the performance of a water sustainability standard for industries. Water, 11(12), 2608. https://doi.org/10.3390/w11122608
• Maheshwari, B. L. (2019). Rainwater harvesting impacts on crop yield: a review with a case study of Tamil Nadu, India. Water, 11(5), 1018. https://doi.org/10.3390/w11051018

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Direct discharge of sewage

Developments in sewage treatment.

• Sources of water pollution
• Types of sewage
• Organic material
• Suspended solids
• Plant nutrients
• Combined systems
• Separate systems
• Alternative systems
• Primary treatment
• Trickling filter
• Activated sludge
• Oxidation pond
• Rotating biological contacter
• Effluent polishing
• Removal of plant nutrients
• Land treatment
• Clustered wastewater treatment systems
• On-site septic tanks and leaching fields
• Wastewater reuse
• Improved treatment methods
• Environmental considerations

What are the common pollutants present in wastewater?

How is wastewater processed at a sewage treatment facility, why is wastewater resource recovery important.

wastewater treatment

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• United States Environmental Protection Agency - How Wastewater Treatment Works...The Basics
• Academia - Wastewater Treatment Design
• Chemistry LibreTexts - Wastewater and Sewage Treatment
• Food and Agriculture Organization of the United Nations - Wastewater treatment
• National Center for Biotechnology Information - PubMed Central - Wastewater Treatment &Water Reclamation
• USGS - Water Science School - Wastewater Treatment Water Use
• Table Of Contents

What is wastewater?

Wastewater is the polluted form of water generated from rainwater runoff and human activities. It is also called sewage. It is typically categorized by the manner in which it is generated—specifically, as domestic sewage, industrial sewage, or storm sewage (stormwater).

How is wastewater generated?

• Domestic wastewater results from water use in residences, businesses, and restaurants.
• Industrial wastewater comes from discharges by manufacturing and chemical industries.
• Rainwater in urban and agricultural areas picks up debris, grit, nutrients, and various chemicals, thus contaminating surface runoff water.

Wastewater contains a wide range of contaminants. The quantities and concentrations of these substances depend upon their source. Pollutants are typically categorized as physical, chemical, and biological. Common pollutants include complex organic materials, nitrogen- and phosphorus-rich compounds, and pathogenic organisms ( bacteria , viruses , and protozoa ). Synthetic organic chemicals, inorganic chemicals, microplastics, sediments, radioactive substances, oil, heat, and many other pollutants may also be present in wastewater.

Sewage treatment facilities use physical, chemical, and biological processes for water purification . The processes used in these facilities are also categorized as preliminary, primary, secondary, and tertiary. Preliminary and primary stages remove rags and suspended solids. Secondary processes mainly remove suspended and dissolved organics. Tertiary methods achieve nutrient removal and further polishing of wastewater. Disinfection, the final step, destroys remaining pathogens. The waste sludge generated during treatment is separately stabilized, dewatered, and sent to landfills or used in land applications.

Wastewater is a complex blend of metals, nutrients, and specialized chemicals. Recovery of these valuable materials can help to offset a community’s growing demands for natural resources. Resource recovery concepts are evolving, and researchers are investigating and developing numerous technologies. Reclamation and reuse of treated water for irrigation , groundwater recharge, or recreational purposes are particular areas of focus.

wastewater treatment , the removal of impurities from wastewater, or sewage, before it reaches aquifers or natural bodies of water such as rivers , lakes , estuaries , and oceans . Since pure water is not found in nature (i.e., outside chemical laboratories), any distinction between clean water and polluted water depends on the type and concentration of impurities found in the water as well as on its intended use. In broad terms, water is said to be polluted when it contains enough impurities to make it unfit for a particular use, such as drinking, swimming, or fishing. Although water quality is affected by natural conditions, the word pollution usually implies human activity as the source of contamination. Water pollution , therefore, is caused primarily by the drainage of contaminated wastewater into surface water or groundwater , and wastewater treatment is a major element of water pollution control .

Historical background

Many ancient cities had drainage systems, but they were primarily intended to carry rainwater away from roofs and pavements. A notable example is the drainage system of ancient Rome . It included many surface conduits that were connected to a large vaulted channel called the Cloaca Maxima (“Great Sewer”), which carried drainage water to the Tiber River . Built of stone and on a grand scale, the Cloaca Maxima is one of the oldest existing monuments of Roman engineering.

There was little progress in urban drainage or sewerage during the Middle Ages. Privy vaults and cesspools were used, but most wastes were simply dumped into gutters to be flushed through the drains by floods. Toilets (water closets) were installed in houses in the early 19th century, but they were usually connected to cesspools, not to sewers . In densely populated areas, local conditions soon became intolerable because the cesspools were seldom emptied and frequently overflowed. The threat to public health became apparent. In England in the middle of the 19th century, outbreaks of cholera were traced directly to well-water supplies contaminated with human waste from privy vaults and cesspools. It soon became necessary for all water closets in the larger towns to be connected directly to the storm sewers. This transferred sewage from the ground near houses to nearby bodies of water. Thus, a new problem emerged: surface water pollution.

It used to be said that “the solution to pollution is dilution.” When small amounts of sewage are discharged into a flowing body of water, a natural process of stream self-purification occurs. Densely populated communities generate such large quantities of sewage, however, that dilution alone does not prevent pollution. This makes it necessary to treat or purify wastewater to some degree before disposal.

The construction of centralized sewage treatment plants began in the late 19th and early 20th centuries, principally in the United Kingdom and the United States . Instead of discharging sewage directly into a nearby body of water, it was first passed through a combination of physical, biological, and chemical processes that removed some or most of the pollutants. Also beginning in the 1900s, new sewage-collection systems were designed to separate storm water from domestic wastewater, so that treatment plants did not become overloaded during periods of wet weather.

After the middle of the 20th century, increasing public concern for environmental quality led to broader and more stringent regulation of wastewater disposal practices. Higher levels of treatment were required. For example, pretreatment of industrial wastewater, with the aim of preventing toxic chemicals from interfering with the biological processes used at sewage treatment plants, often became a necessity. In fact, wastewater treatment technology advanced to the point where it became possible to remove virtually all pollutants from sewage. This was so expensive, however, that such high levels of treatment were not usually justified.

Wastewater treatment plants became large, complex facilities that required considerable amounts of energy for their operation. After the rise of oil prices in the 1970s, concern for energy conservation became a more important factor in the design of new pollution control systems. Consequently, land disposal and subsurface disposal of sewage began to receive increased attention where feasible . Such “low-tech” pollution control methods not only might help to conserve energy but also might serve to recycle nutrients and replenish groundwater supplies.

Essay on Wastage of Water

Students are often asked to write an essay on Wastage of Water in their schools and colleges. And if you’re also looking for the same, we have created 100-word, 250-word, and 500-word essays on the topic.

Let’s take a look…

100 Words Essay on Wastage of Water

Introduction.

Water is a precious resource, yet we often waste it. This wastage not only depletes our water supplies but also affects our environment.

Causes of Water Wastage

Water wastage happens in many ways. We leave taps running, overwater plants, and take long showers. Industries also waste water during production processes.

Impacts of Water Wastage

Wasting water leads to scarcity, affecting people and wildlife. It also increases energy use in water treatment plants, contributing to climate change.

We must value water and reduce wastage. Small changes can make a big difference, ensuring water for future generations.

250 Words Essay on Wastage of Water

Introduction: the value of water.

Water, the elixir of life, forms the lifeblood of our planet. Yet, it is often taken for granted, leading to its rampant wastage. This essay explores the profound implications of water wastage and the need for efficient water management.

The Scale of Water Wastage

The magnitude of water wastage is alarming, with millions of gallons wasted each day through leaks, inefficient appliances, and thoughtless consumption. A significant portion of the population lacks access to clean drinking water, illustrating a stark contrast between wastage and necessity.

Consequences of Water Wastage

The repercussions of water wastage are multidimensional, affecting both humans and the environment. It exacerbates water scarcity, impacts food production, and disrupts ecosystems. Additionally, it contributes to energy wastage, as substantial energy is required to process and deliver water.

The Urgency of Water Conservation

Water conservation is not a choice but a necessity. It is essential to develop and implement efficient water management strategies, such as rainwater harvesting, wastewater treatment, and efficient irrigation practices. Furthermore, individual actions like mindful consumption and regular checks for leaks can make a significant difference.

Conclusion: A Collective Responsibility

Water wastage is a critical issue that demands immediate attention. It is a collective responsibility to ensure the judicious use of water, and every drop saved contributes to a sustainable future. As the African proverb goes, “A drop of water is worth more than a sack of gold to a thirsty man.” Let’s value it accordingly.

500 Words Essay on Wastage of Water

The scourge of water wastage.

Water, a resource vital to life on Earth, is being wasted at an alarming rate. Despite its crucial role in sustaining life, we often take its availability for granted. The wastage of water is an issue of global concern that needs immediate attention.

Understanding the Gravity of the Problem

The World Health Organization estimates that nearly 2.2 billion people globally lack access to safely managed drinking water services. Yet, in parts of the world where water is abundant, it is often wasted. This wastage is not only unethical but also exacerbates water scarcity issues in areas already grappling with water shortage.

The Sources of Water Wastage

Water wastage is not confined to any one area of human activity. It permeates through various sectors, including agriculture, industry, and households. Inefficient irrigation systems, leaky pipes, and overuse of water in industry contribute significantly to water wastage. In households, activities like long showers, running taps while brushing, and overuse of washing machines are common examples of water wastage.

The Environmental Impact

Water wastage has far-reaching environmental consequences. It contributes to the depletion of freshwater resources, leading to water scarcity. This scarcity, in turn, threatens biodiversity as freshwater habitats dry up. Furthermore, over-extraction of groundwater to meet excessive water demand can lead to land subsidence and other geological issues.

Addressing the Issue

The role of education.

Education plays a pivotal role in combatting water wastage. By raising awareness about the importance of water conservation and the consequences of wastage, we can foster a culture of responsible water usage. Schools and universities can incorporate water conservation education into their curriculum, and public campaigns can be launched to reach a broader audience.

In conclusion, the issue of water wastage is a pressing concern that needs to be addressed urgently. Through a combination of individual action, policy changes, technological innovation, and education, we can make significant strides in reducing water wastage and ensuring the sustainable use of this vital resource. The future of our planet and generations to come depends on our ability to responsibly manage and conserve water.

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Revision Notes on Wastewater Story

Water pollution.

When the water present on earth in the oceans, seas, rivers, lakes, ponds and under the ground gets contaminated, it is termed as water pollution. The contamination of water results in a change in its physical, biological and chemical properties and hence makes it unsafe for drinking or usage of other purposes. The substances that cause water pollution are called Water Pollutants . The pollution of water can lead to serious effects such as diseases, an effect on the ecosystem of a region, and loss of aquatic life.

Major Water Pollutants

Sewage: a massive amount of wastewater or sewage is dumped into water bodies such as rivers and seas which pollutes their freshwater and makes it inappropriate for any kind of consumption due to the rise of several bacteria and other microorganisms. It not only affects the aquatic life of the water body but also leads to severe diseases like cholera, diarrhoea and typhoid.

Industrial Chemical Wastes: Harmful chemicals such as lead and mercury are often dumped by industries into the water bodies directly which contaminate their water.

Agricultural Effluents: Fertilizers, pesticides, insecticides and farm wastes are often washed off by the rain to the water bodies and contaminate the water.

Oil Spills: Oil spills often occur due to accidents and leakages of oil in the sea which leads to loss of aquatic life.

Thermal Wastes: Thermal industries often spill warm water in the water bodies which decreases its oxygen content. It also leads to a rise in temperature of water which is not suitable for aquatic animals.

Suspended Solids: They come from soil erosion, untreated sewage and mining. These suspended pollutants block the sunlight from reaching the aquatic plants and animals.

What is wastewater?

The water that has been used and is not fit for usage again is called Wastewater . It is dirty water from the laundry, toilets, sinks and drains.

Water - Our Lifeline

Figure 1: Usage of clean water

We all need clean water however, not all can access the same.

Hence, it is necessary not only to preserve water but clean the used water before dumping it into the seas or any other water body.

This is why the United Nations proclaimed the period between 2005 and 2015 as the International decade for action on ‘water for life’.

What do you mean by cleaning of water?

It is a process in which the pollutants from the water are removed before the water reaches a water body or before it is used again. This process is also called Sewage Treatment .

What is sewage?

Wastewater from houses, offices, Industries, hospitals and other sources is called Sewage .

Rainwater that flows into the drains during heavy rainfalls is also sewage because it contains pollutants that it washes off from the roads.

Any liquid waste can be called sewage.

Sewage water contains impurities mixed into it as well as some suspended pollutants.

These impurities present in the sewage are called Contaminants as they contaminate the water. 

Figure 2: Sewage is a mixture of impurities

Water freshens up - An Eventful Journey

Sewers - Large and small pipes that are installed in buildings to carry sewage water are sewers.

Sewerage - A network or transport system consisting of sewers is called Sewerage .

It carries sewage water from the point where it is produced to the point where it is disposed (treatment plant).

It consists of manholes that are located at every 50 to 60 metres.

The manholes are installed at a point where two or more sewers intersect or change their directions.

Every locality has as a system that allows removal of waste from the houses and industries.

Figure 3: Sewerage

Wastewater Treatment Plant (WWTP)

Wastewater includes biological, physical and chemical matter and hence involves biological, physical and chemical processes of removal of the contaminants.

The physical and biological process of treatment of water:

1. Separation of Large Objects from Sewage Water

The wastewater is first passed through bar screens which remove big objects from the water like plastic bottles, napkins, rags, cans and sticks.

Figure 4: Bar Screens

2. Separation of Sand and Dirt

The wastewater is then sent to a grit and sand removal tank . The speed of the water is decreased at this step. This allows the sand, dirt and pebbles to settle down.

3. Removal of Solids

Now the water cycles in a tank called Clarifier which is sloped in the centre. This lets the solids like faeces to settle at the bottom. This is called Sludge .

The sludge is then separated from the water with the help of a Scrapper .

Substances like oil and grease are removed with the help of a Skimmer as they float above the water. In this step clarified water is obtained.

The sludge so obtained is passed into a tank where anaerobic bacteria can decompose it and produce biogas. The biogas is then used as a fuel.

Figure 5: Sand and Girt Removal Tank

4. Suspended Sludge Removal

The clarified water also needs to be cleaned further. Hence, it is moved to an aerator that pumps air into it.

This allows aerobic bacteria to grow in this water.

The aerobic bacteria consume organic waste, soaps, food waste and other elements that remain in the clarified water.

This water is allowed to settle for several hours and then these waste materials settle down in the tank. This is called Activated Sludge .

The water is removed from the top of this sludge with the help of machines or sand drying beds. The sludge is then dried and can be used as manure.

Figure 6: Aerator

This treated water contains fewer amounts of impurities and suspended matter. This water is safe to dump into a water body or under the ground. Hence, it is then discharged into a sea, river or underground. Nature further cleans it up.

Chemical Treatment of Wastewater:

Sometimes harmful chemicals can be present in the water even after treating them physically and biologically.

These chemicals are therefore removed by using disinfectants such as chlorine and Ozone .

Often chlorine gas or ozone gas is introduced in this water which purifies it chemically.

Figure 7: WWTP

Eucalyptus Plant and Cleaning of Water

Eucalyptus plants can absorb the water at a faster rate and then they release pure water vapour. In this way, they act as a natural water purifier. Hence, it is advised to plant Eucalyptus trees along the sewage ponds.

Figure 8: Eucalyptus Plant

Why should we adopt better housekeeping practices and become an active citizen?

We should try to reduce the waste that produced in our households so that there is not much pressure on WWTP. It is often difficult to clean tons of wastewater.

The sewage water can cause several problems such as harmful diseases, unhygienic and unsanitary conditions in the locality.

Hence, we can be more considerate about producing a limited amount of waste and we can accomplish this by adopting better housekeeping practices.

Also, we can become an active citizen by making sure that there are no open drains or sewers in our locality. If we find any we should immediately report the same to the municipality.

What better housekeeping practices we can adopt?

A good way to minimise the sewage water is to check what is going in our drains. If we dispose of our waste properly we may be able to reduce the sewage. Here are some housekeeping practices that we should adopt:

We should through all the oil and fats in dustbin rather than throwing them of the dream. Oil and fats harden and block the drains. Moreover, it is difficult to separate them from the water.

We should not throw chemicals in the drains like insecticides, pesticides or medicines. They can kill the microbes in the water that help in its purification.

We should not throw things in the drain that can block them like tea leaves, food remains, cotton, soft toys etc. We should always through them in the dustbin.

Figure 9: Treating Water at home

Sanitation and Disease

Sanitation refers to the health conditions of people related to the disposal of sewage, human excreta and provision of clean drinking water.

Poor sanitation and polluted drinking water can lead to many diseases.

Hence, a sanitation system aims to provide a clean environment for us so that we can stay away from diseases.

Improper sanitation can give rise to different diseases that arise from contaminated water such as typhoid, dysentery, hepatitis, polio, cholera and meningitis.

The human excreta is a health hazard and can lead to soil and water pollution. It can pollute the surface water and groundwater. Hence, people should never defecate in open areas.

Alternative Arrangement for Sewage Disposal

• As an alternative for sewage disposal on-site sewage is being used nowadays, for example, septic tanks, compost pit toilets and chemical toilets.
• The onsite sewage treatments use natural procedures to treat and dispose of the wastewater or sewage.

Septic Tanks – A septic tank is often installed under the ground in houses or buildings such as hospitals. It allows decomposition of sewage from home through the action of anaerobic bacteria.

Chemical Toilets – A chemical toilet has a separate compartment that treats human waste with chemicals and decreases their odour.

Composting Toilets – A composting toilet treats human waste with biological processes. The aerobic bacteria are present in a storage tank that act upon the waste and turn it into compost.

Many organizations have also installed on-site hygienic waste disposal technology in which the human excreta directly flows into a biogas plant and is then used as an energy resource.

Sanitation at Public Places

There are numerous places in our country which are very busy such as airports, railway stations and bus depots.

Many times large gatherings such as fairs and festivals are also organized where a large number of people visits.

This results in the generation of large amounts of waste and if the waste is not treated properly it can lead to several diseases and even an epidemic.

Hence we should all become aware and contribute to maintaining sanitation not only in our homes but also at public places.

If we adopt certain practices at public places we can help in maintaining their sanitation, for instance:

We should not throw garbage in public places and always use the dustbins.

We should not spit around in a public place.

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Wastewater Treatment and Reuse: a Review of its Applications and Health Implications

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• Published: 10 May 2021
• Volume 232 , article number  208 , ( 2021 )

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• Kavindra Kumar Kesari   ORCID: orcid.org/0000-0003-3622-9555 1   na1 ,
• Ramendra Soni 2   na1 ,
• Qazi Mohammad Sajid Jamal 3 ,
• Pooja Tripathi 4 ,
• Jonathan A. Lal 2 ,
• Niraj Kumar Jha 5 ,
• Mohammed Haris Siddiqui 6 ,
• Pradeep Kumar 7 ,
• Vijay Tripathi 2 &
• Janne Ruokolainen 1  

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Water scarcity is one of the major problems in the world and millions of people have no access to freshwater. Untreated wastewater is widely used for agriculture in many countries. This is one of the world-leading serious environmental and public health concerns. Instead of using untreated wastewater, treated wastewater has been found more applicable and ecofriendly option. Moreover, environmental toxicity due to solid waste exposures is also one of the leading health concerns. Therefore, intending to combat the problems associated with the use of untreated wastewater, we propose in this review a multidisciplinary approach to handle wastewater as a potential resource for use in agriculture. We propose a model showing the efficient methods for wastewater treatment and the utilization of solid wastes in fertilizers. The study also points out the associated health concern for farmers, who are working in wastewater-irrigated fields along with the harmful effects of untreated wastewater. The consumption of crop irrigated by wastewater has leading health implications also discussed in this review paper. This review further reveals that our current understanding of the wastewater treatment and use in agriculture with addressing advancements in treatment methods has great future possibilities.

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1 Introduction

Rapidly depleting and elevating the level of freshwater demand, though wastewater reclamation or reuse is one of the most important necessities of the current scenario. Total water consumption worldwide for agriculture accounts 92% (Clemmens et al., 2008 ; Hoekstra & Mekonnen, 2012 ; Tanji & Kielen, 2002 ). Out of which about 70% of freshwater is used for irrigation (WRI, 2020 ), which comes from the rivers and underground water sources (Pedrero et al., 2010 ). The statistics shows serious concern for the countries facing water crisis. Shen et al. ( 2014 ) reported that 40% of the global population is situated in heavy water–stressed basins, which represents the water crisis for irrigation. Therefore, wastewater reuse in agriculture is an ideal resource to replace freshwater use in agriculture (Contreras et al., 2017 ). Treated wastewater is generally applied for non-potable purposes, like agriculture, land, irrigation, groundwater recharge, golf course irrigation, vehicle washing, toilet flushes, firefighting, and building construction activities. It can also be used for cooling purposes in thermal power plants (Katsoyiannis et al., 2017 ; Mohsen, 2004 ; Smith, 1995 ; Yang et al., 2017 ). At global level, treated wastewater irrigation supports agricultural yield and the livelihoods of millions of smallholder farmers (Sato et al., 2013 ). Global reuse of treated wastewater for agricultural purposes shows wide variability ranging from 1.5 to 6.6% (Sato et al., 2013 ; Ungureanu et al., 2018 ). More than 10% of the global population consumes agriculture-based products, which are cultivated by wastewater irrigation (WHO, 2006 ). Treated wastewater reuse has experienced very rapid growth and the volumes have been increased ~10 to 29% per year in Europe, the USA, China, and up to 41% in Australia (Aziz & Farissi, 2014 ). China stands out as the leading country in Asia for the reuse of wastewater with an estimated 1.3 M ha area including Vietnam, India, and Pakistan (Zhang & Shen, 2017 ). Presently, it has been estimated that, only 37.6% of the urban wastewater in India is getting treated (Singh et al., 2019 ). By utilizing 90% of reclaimed water, Israel is the largest user of treated wastewater for agriculture land irrigation (Angelakis & Snyder, 2015 ). The detail information related to the utilization of freshwater and treated wastewater is compiled in Table 1 .

Many low-income countries in Africa, Asia, and Latin America use untreated wastewater as a source of irrigation (Jiménez & Asano, 2008 ). On the other hand, middle-income countries, such as Tunisia, Jordan, and Saudi Arabia, use treated wastewater for irrigation (Al-Nakshabandi et al., 1997 ; Balkhair, 2016a ; Balkhair, 2016b ; Qadir et al., 2010 ; Sato et al., 2013 ).

Domestic water and treated wastewater contains various type of nutrients such as phosphorus, nitrogen, potassium, and sulfur, but the major amount of nitrogen and phosphorous available in wastewater can be easily accumulated by the plants, that’s why it is widely used for the irrigation (Drechsel et al., 2010 ; Duncan, 2009 ; Poustie et al., 2020 ; Sengupta et al., 2015 ). The rich availability of nutrients in reclaimed wastewater reduces the use of fertilizers, increases crop productivity, improves soil fertility, and at the same time, it may also decrease the cost of crop production (Chen et al., 2013 a; Jeong et al., 2016 ). The data of high nutritional values in treated wastewater is shown in Fig. 1 .

Nutrient concentrations (mg/L) of freshwater/wastewater (Yadav et al., 2002 )

Wastewater reuse for crop irrigation showed several health concerns (Ungureanu et al., 2020 ). Irrigation with the industrial wastewater either directly or mixing with domestic water showed higher risk (Chen et al., 2013). Risk factors are higher due to heavy metal and pathogens contamination because heavy metals are non-biodegradable and have a long biological half-life (Chaoua et al., 2019 ; WHO, 2006 ). It contains several toxic elements, i.e., Cu, Cr, Mn, Fe, Pb, Zn, and Ni (Mahfooz et al., 2020 ). These heavy metals accumulate in topsoil (at a depth of 20 cm) and sourcing through plant roots; they enter the human and animal body through leafy vegetables consumption and inhalation of contaminated soils (Mahmood et al., 2014 ). Therefore, health risk assessment of such wastewater irrigation is important especially in adults (Mehmood et al., 2019 ; Njuguna et al., 2019 ; Xiao et al., 2017 ). For this, an advanced wastewater treatment method should be applied before release of wastewater in the river, agriculture land, and soils. Therefore, this review also proposed an advance wastewater treatment model, which has been tasted partially at laboratory scale by Kesari and Behari ( 2008 ), Kesari et al. ( 2011a , b ), and Kumar et al. ( 2010 ).

For a decade, reuse of wastewater has also become one of the global health concerns linking to public health and the environment (Dang et al., 2019 ; Narain et al., 2020 ). The World Health Organization (WHO) drafted guidelines in 1973 to protect the public health by facilitating the conditions for the use of wastewater and excreta in agriculture and aquaculture (WHO, 1973 ). Later in 2005, the initial guidelines were drafted in the absence of epidemiological studies with minimal risk approach (Carr, 2005 ). Although, Adegoke et al. ( 2018 ) reviewed the epidemiological shreds of evidence and health risks associated with reuse of wastewater for irrigation. Wastewater or graywater reuse has adverse health risks associated with microbial hazards (i.e., infectious pathogens) and chemicals or pharmaceuticals exposures (Adegoke et al., 2016 ; Adegoke et al., 2017 ; Busgang et al., 2018 ; Marcussen et al., 2007 ; Panthi et al., 2019 ). Researchers have reported that the exposure to wastewater may cause infectious (helminth infection) diseases, which are linked to anemia and impaired physical and cognitive development (Amoah et al., 2018 ; Bos et al., 2010 ; Pham-Duc et al., 2014 ; WHO, 2006 ).

Owing to an increasing population and a growing imbalance in the demand and supply of water, the use of wastewater has been expected to increase in the coming years (World Bank, 2010 ). The use of treated wastewater in developed nations follows strict rules and regulations. However, the direct use of untreated wastewater without any sound regulatory policies is evident in developing nations, which leads to serious environmental and public health concerns (Dickin et al., 2016 ). Because of these issues, we present in this review, a brief discussion on the risk associated with the untreated wastewater exposures and advanced methods for its treatment, reuse possibilities of the treated wastewater in agriculture.

2 Environmental Toxicity of Untreated Wastewater

Treated wastewater carries larger applicability such as irrigation, groundwater recharge, toilet flushing, and firefighting. Municipal wastewater treatment plants (WWTPs) are the major collection point for the different toxic elements, pathogenic microorganisms, and heavy metals. It collects wastewater from divergent sources like household sewage, industrial, clinical or hospital wastewater, and urban runoff (Soni et al., 2020 ). Alghobar et al. ( 2014 ) reported that grass and crops irrigated with sewage and treated wastewater are rich in heavy metals in comparison with groundwater (GW) irrigation. Although, heavy metals classified as toxic elements and listed as cadmium, lead, mercury, copper, and iron. An exceeding dose or exposures of these heavy metals could be hazardous for health (Duan et al., 2017 ) and ecological risks (Tytła, 2019 ). The major sources of these heavy metals come from drinking water. This might be due to the release of wastewater into river or through soil contamination reaches to ground water. Table 2 presenting the permissible limits of heavy metals presented in drinking water and its impact on human health after an exceeding the amount in drinking water, along with the route of exposure of heavy metals to human body.

Direct release in river or reuse of wastewater for irrigation purposes may create short-term implications like heavy metal and microbial contamination and pathogenic interaction in soil and crops. It has also long-term influence like soil salinity, which grows with regular use of untreated wastewater (Smith, 1995 ). Improper use of wastewater for irrigation makes it unsafe and environment threatening. Irrigation with several different types of wastewater, i.e., industrial effluents, municipal and agricultural wastewaters, and sewage liquid sludge transfers the heavy metals to the soil, which leads to accumulation in crops due to improper practices. This has been identified as a significant route of heavy metals into aquatic resources (Agoro et al., 2020 ). Hussain et al. ( 2019 ) investigated the concentration of heavy metals (except for Cd) was higher in the soil irrigated with treated wastewater (large-scale sewage treatment plant) than the normal ground water, also reported by Khaskhoussy et al. ( 2015 ).

In other words, irrigation with wastewater mitigates the quality of crops and enhances health risks. Excess amount of copper causes anemia, liver and kidney damage, vomiting, headache, and nausea in children (Bent & Bohm, 1995 ; Madsen et al., 1990 ; Salem et al., 2000 ). A higher concentration of arsenic may lead to bone and kidney cancer (Jarup, 2003 ) and results in osteopenia or osteoporosis (Puzas et al., 2004 ). Cadmium gives rise to musculoskeletal diseases (Fukushima et al., 1970 ), whereas mercury directly affects the nervous system (Azevedo et al., 2014 ).

3 Spread of Antibiotic Resistance

Currently, antibiotics are highly used for human disease treatment; however, uses in poultries, animal husbandries, biochemical industries, and agriculture are common practices these days. Extensive use and/or misuse of antibiotics have given rise to multi-resistant bacteria, which carry multiple resistance genes (Icgen & Yilmaz, 2014 ; Lv et al., 2015 ; Tripathi & Tripathi, 2017 ; Xu et al., 2017 ). These multidrug-resistant bacteria discharged through the sewage network and get collected into the wastewater treatment plants. Therefore, it can be inferred that the WWTPs serve as the hotspot of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Though, these antibiotic-resistant bacteria can be disseminated to the different bacterial species through the mobile genetic elements and horizontal gene transfer (Gupta et al., 2018 ). Previous studies indicated that certain pathogens might survive in wastewater, even during and after the treatment processes, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) (Börjesson et al., 2009 ; Caplin et al., 2008 ). The use of treated wastewater in irrigation provides favorable conditions for the growth and persistence of total coliforms and fecal coliforms (Akponikpe et al., 2011 ; Sacks & Bernstein, 2011 ). Furthermore, few studies have also reported the presence of various bacterial pathogens, such as Clostridium , Salmonella , Streptococci , Viruses, Protozoa, and Helminths in crops irrigated with treated wastewater (Carey et al., 2004 ; Mañas et al., 2009 ; Samie et al., 2009 ). Goldstein ( 2013 ) investigated the survival of ARB in secondary treated wastewater and proved that it causes serious health risks to the individuals, who are exposed to reclaimed water. The U.S. Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) have already declared the ARBs as the imminent hazard to human health. According to the list published by WHO, regarding the development of new antimicrobial agents, the ESKAPE ( Enterococcus faecium , S. aureus , Klebsiella pneumoniae , Acinetobacter baumannii , Pseudomonas aeruginosa , and Enterobacter species) pathogens were designated to be “priority status” as their occurrence in the food chain is considered as the potential and major threat for the human health (Tacconelli et al., 2018 ).

These ESKAPE pathogens have acquired the multi drug resistance mechanisms against oxazolidinones, lipopeptides, macrolides, fluoroquinolones, tetracyclines, β-lactams, β-lactam–β-lactamase inhibitor combinations, and even those antibiotics that are considered as the last line of defense, including carbapenems and glycopeptides (Giddins et al., 2017 ; Herc et al., 2017 ; Iguchi et al., 2016 ; Naylor et al., 2018 ; Zaman et al., 2017 ), by the means of genetic mutation and mobile genetic elements. These cluster of ESKAPE pathogens are mainly responsible for lethal nosocomial infections (Founou et al., 2017 ; Santajit & Indrawattana, 2016 ).

Due to the wide application of antibiotics in animal husbandry and inefficient capability of wastewater treatment plants, the multidrug-resistant bacteria such as tetracyclines, sulfonamides, β-lactam, aminoglycoside, colistin, and vancomycin in major are disseminated in the receiving water bodies, which ultimately results in the accumulation of ARGs in the irrigated crops (He et al., 2020 ).

4 Toxic Contaminations in Wastewater Impacting Human Health

The release of untreated wastewater into the river may pose serious health implications (König et al., 2017 ; Odigie, 2014 ; Westcot, 1997 ). It has been already discussed about the household and municipal sewage which contains a major amount of organic materials and pathogenic microorganisms and these infectious microorganisms are capable of spreading various diseases like typhoid, dysentery, diarrhea, vomiting, and malabsorption (Jia & Zhang, 2020 ; Numberger et al., 2019 ; Soni et al., 2020 ). Additionally, pharmaceutical industries also play a key role in the regulation and discharge of biologically toxic agents. The untreated wastewater also contains a group of contaminants, which are toxic to humans. These toxic contaminations have been classified into two major groups: (i) chemical contamination and (ii) microbial contamination.

4.1 Chemical Contamination

Mostly, various types of chemical compounds released from industries, tanneries, workshops, irrigated lands, and household wastewaters are responsible for several diseases. These contaminants can be organic materials, hydrocarbons, volatile compounds, pesticides, and heavy metals. Exposure to such contaminants may cause infectious diseases like chronic dermatoses and skin cancer, lung infection, and eye irritation. Most of them are non-biodegradable and intractable. Therefore, they can persist in the water bodies for a very long period and could be easily accumulated in our food chain system. Several pharmaceutical personal care products (PPCPs) and surfactants are available that may contain toxic compounds like nonylphenol, estrone, estradiol, and ethinylestradiol. These compounds are endocrine-disrupting chemicals (Bolong et al., 2009 ), and the existence of these compounds in the human body even in the trace amounts can be highly hazardous. Also, the occurrence of perfluorinated compounds (PFCs) in wastewater, which is toxic in nature, has been significantly reported worldwide (Templeton et al., 2009 ). Furthermore, PFCs cause severe health menaces like pre-eclampsia, birth defects, reduced human fertility (Webster, 2010 ), immunotoxicity (Dewitt et al., 2012 ), neurotoxicity (Lee & Viberg, 2013 ), and carcinogenesis (Bonefeld-Jorgensen et al., 2011 ).

4.2 Microbial Contamination

Researchers have reported serious health risks associated with the microbial contaminants in untreated wastewater. The diverse group of microorganisms causes severe health implications like campylobacteriosis, diarrhea, encephalitis, typhoid, giardiasis, hepatitis A, poliomyelitis, salmonellosis, and gastroenteritis (ISDH, 2009 ; Okoh et al., 2010 ). Few bacterial species like P. aeruginosa , Salmonella typhimurium , Vibrio cholerae , G. intestinales , Legionella spp., E. coli , Shigella sonnei have been reported for the spreading of waterborne diseases, and acute illness in human being (Craun et al., 2006 ; Craun et al., 2010 ). These aforementioned microorganisms may release in the environment from municipal sewage water network, animal husbandries, or hospitals and enter the food chain via public water supply systems.

5 Wastewater Impact on Agriculture

The agriculture sector is well known for the largest user of water, accounting for nearly 70% of global water usage (Winpenny et al., 2010 ). The fact that an estimated 20 million hectares worldwide are irrigated with wastewater suggests a major source for irrigation (Ecosse, 2001 ). However, maximum wastewater that is used for irrigation is untreated (Jiménez & Asano, 2008 ; Scott et al., 2004 ). Mostly in developing countries, partially treated or untreated wastewater is used for irrigation purpose (Scott et al., 2009 ). Untreated wastewater often contains a large range of chemical contaminants from waste sites, chemical wastes from industrial discharges, heavy metals, fertilizers, textile, leather, paper, sewage waste, food processing waste, and pesticides. World Health Organization (WHO) has warned significant health implications due to the direct use of wastewater for irrigation purposes (WHO, 2006 ). These contaminants pose health risks to communities (farmers, agricultural workers, their families, and the consumers of wastewater-irrigated crops) living in the proximity of wastewater sources and areas irrigated with untreated wastewater (Qadir et al., 2010 ). Wastewater also contains a wide variety of organic compounds. Some of them are toxic or cancer-causing and have harmful effects on an embryo (Jarup, 2003 ; Shakir et al., 2016 ). The pathway of untreated wastewater used in irrigation and associated health effects are shown in Fig. 2 .

Exposure pathway representing serious health concerns from wastewater-irrigated crops

Alternatively, in developing countries, due to the limited availability of treatment facilities, untreated wastewater is discharged into the existing waterbodies (Qadir et al., 2010 ). The direct use of wastewater in agriculture or irrigation obstructs the growth of natural plants and grasses, which in turn causes the loss of biodiversity. Shuval et al. ( 1985 ) reported one of the earliest evidences connecting to agricultural wastewater reuse with the occurrence of diseases. Application of untreated wastewater in irrigation increases soil salinity, land sealing followed by sodium accumulation, which results in soil erosion. Increased soil salinity and sodium accumulation deteriorates the soil and decreases the soil permeability, which inhibits the nutrients intake of crops from the soil. These causes have been considered the long-term impact of wastewater reuse in agriculture (Halliwell et al., 2001 ). Moreover, wastewater contaminated soils are a major source of intestinal parasites (helminths—nematodes and tapeworms) that are transmitted through the fecal–oral route (Toze, 1997 ). Already known, the helminth infections are linked to blood deficiency and behavioral or cognitive development (Bos et al., 2010 ). One of the major sources of helminth infections around the world is the use of raw or partially treated sewage effluent and sludge for the irrigation of food crops (WHO, 1989 ). Wastewater-irrigated crops contain heavy metal contamination, which originates from mining, foundries, and metal-based industries (Fazeli et al., 1998 ). Exposure to heavy metals including arsenic, cadmium, lead, and mercury in wastewater-irrigated crops is a cause for various health problems. For example, the consumption of high amounts of cadmium causes osteoporosis in humans (Dickin et al., 2016 ). The uptake of heavy metals by the rice crop irrigated with untreated effluent from a paper mill has been reported to cause serious health concerns (Fazeli et al., 1998 ). Irrigating rice paddies with highly contaminated water containing heavy metals leads to the outbreak of Itai-itai disease in Japan (Jarup, 2003 ).

Owing to these widespread health risks, the WHO published the third edition of its guidelines for the safe use of wastewater in irrigating crops (WHO, 2006 ) and made recommendations for threshold contaminant levels in wastewater. The quality of wastewater for agricultural reuse have been classified based on the availability of nutrients, trace elements, microorganisms, and chemicals contamination levels. The level of contamination differs widely depending on the type of source, household sewage, pharmaceutical, chemical, paper, or textile industries effluents. The standard measures of water quality for irrigation are internationally reported (CCREM, 1987 ; FAO, 1985 ; FEPA, 1991 ; US EPA, 2004 , 2012 ; WHO, 2006 ), where the recommended levels of trace elements, metals, COD, BOD, nitrogen, and phosphorus are set at certain limits. Researchers reviewed the status of wastewater reuse for agriculture, based on its standards and guidelines for water quality (Angelakis et al., 1999 ; Brissaud, 2008 ; Kalavrouziotis et al., 2015 ). Based on these recommendations and guidelines, it is evident that greater awareness is required for the treatment of wastewater safely.

6 Wastewater Treatment Techniques

6.1 primary treatment.

This initial step is designed to remove gross, suspended and floating solids from raw wastewater. It includes screening to trap solid objects and sedimentation by gravity to remove suspended solids. This physical solid/liquid separation is a mechanical process, although chemicals can be used sometimes to accelerate the sedimentation process. This phase of the treatment reduces the BOD of the incoming wastewater by 20–30% and the total suspended solids by nearly 50–60%.

6.2 Secondary (Biological) Treatment

This stage helps eliminate the dissolved organic matter that escapes primary treatment. Microbes consume the organic matter as food, and converting it to carbondioxide, water, and energy for their own growth. Additional settling to remove more of the suspended solids then follows the biological process. Nearly 85% of the suspended solids and biological oxygen demand (BOD) can be removed with secondary treatment. This process also removes carbonaceous pollutants that settle down in the secondary settling tank, thus separating the biological sludge from the clear water. This sludge can be fed as a co-substrate with other wastes in a biogas plant to obtain biogas, a mixture of CH 4 and CO 2 . It generates heat and electricity for further energy distribution. The leftover, clear water is then processed for nitrification or denitrification for the removal of carbon and nitrogen. Furthermore, the water is passed through a sedimentation basin for treatment with chlorine. At this stage, the water may still contain several types of microbial, chemical, and metal contaminations. Therefore, to make the water reusable, e.g., for irrigation, it further needs to pass through filtration and then into a disinfection tank. Here, sodium hypochlorite is used to disinfect the wastewater. After this process, the treated water is considered safe to use for irrigation purposes. Solid wastes generated during primary and secondary treatment processes are processed further in the gravity-thickening tank under a continuous supply of air. The solid waste is then passed into a centrifuge dewatering tank and finally to a lime stabilization tank. Treated solid waste is obtained at this stage and it can be processed further for several uses such as landfilling, fertilizers and as a building.

Other than the activated sludge process of wastewater treatment, there are several other methods developed and being used in full-scale reactors such as ponds (aerobic, anaerobic, facultative, and maturation), trickling filters, anaerobic treatments like up-flow anaerobic sludge blanket (UASB) reactors, artificial wetlands, microbial fuel cells, and methanogenic reactors.

UASB reactors are being applied for wastewater treatment from a very long period. Behling et al. ( 1996 ) examined the performance of the UASB reactor without any external heat supply. In their study, the COD loading rate was maintained at 1.21 kg COD/m 3 /day, after 200 days of trial. They achieved an average of 85% of COD removal. Von-Sperling and Chernicharo ( 2005 ) presented a combined model consisted of an Up-flow Anaerobic Sludge Blanket-Activated Sludge reactor (UASB–AS system), using the low strength domestic wastewater with a BOD 5 amounting to 340 mg/l. Outcomes of their experiment have shown a 60% reduction in sludge construction and a 40% reduction in aeration energy consumption. In another experiment, Rizvi et al. ( 2015 ) seeded UASB reactor with cow manure dung to treat domestic wastewater; they observed 81%, 75%, and 76% reduction in COD, TSS, and total sulfate removal, respectively, in their results.

6.3 Tertiary or Advanced Treatment Processes

The tertiary treatment process is employed when specific constituents, substances, or contaminants cannot be completely removed after the secondary treatment process. The tertiary treatment processes, therefore, ensure that nearly 99% of all impurities are removed from wastewater. To make the treated water safe for drinking purposes, water is treated individually or in combination with advanced methods like the US (ultrasonication), UV (ultraviolet light treatment), and O 3 (exposure to ozone). This process helps to remove bacteria and heavy metal contaminations remaining in the treated water. For the purpose, the secondarily treated water is first made to undergo ultrasonication and it is subsequently exposed to UV light and passed through an ozone chamber for the complete removal of contaminations. The possible mechanisms by which cells are rendered inviable during the US include free-radical attack and physical disruption of cell membranes (Phull et al., 1997 ; Scherba et al., 1991 ). The combined treatment of US + UV + O 3 produces free radicals, which are attached to cell membranes of the biological contaminants. Once the cell membrane is sheared, chemical oxidants can enter the cell and attack internal structures. Thus, the US alone or in combination facilitates the deagglomeration of microorganisms and increases the efficiency of other chemical disinfectants (Hua & Thompson, 2000 ; Kesari et al., 2011a , b ; Petrier et al., 1992 ; Phull et al., 1997 ; Scherba et al., 1991 ). A combined treatment method was also considered by Pesoutova et al. ( 2011 ) and reported a very effective method for textile wastewater treatment. The effectiveness of ultrasound application as a pre-treatment step in combination with ultraviolet rays (Blume & Neis, 2004 ; Naddeo et al., 2009 ), or also compared it with various other combinations of both ultrasound and UV radiation with TiO 2 photocatalysis (Paleologou et al., 2007 ), and ozone (Jyoti & Pandit, 2004 ) to optimize wastewater disinfection process.

An important aspect of our wastewater treatment model (Fig. 3 ) is that at each step of the treatment process, we recommend the measurement of the quality of treated water. After ensuring that the proper purification standards are met, the treated water can be made available for irrigation, drinking or other domestic uses.

A wastewater treatment schematic highlighting the various methods that result in a progressively improved quality of the wastewater from the source to the intended use of the treated wastewater for irrigation purposes

6.4 Nanotechnology as Tertiary Treatment of Wastewater Converting Drinking Water Alike

Considering the emerging trends of nanotechnology, nanofillers can be used as a viable method for the tertiary treatment of wastewater. Due to the very small pore size, 1–5-nm nanofillers may eliminate the organic–inorganic pollutants, heavy metals, as well as pathogenic microorganisms and pharmaceutically active compounds (PhACs) (Mohammad et al., 2015 ; Vergili, 2013 ). Over the recent years, nanofillers have been largely accepted in the textile industry for the treatment of pulp bleaching pharmaceutical industry, dairy industry, microbial elimination, and removal of heavy metals from wastewater (Abdel-Fatah, 2018 ). Srivastava et al. ( 2004 ) synthesized very efficient and reusable water filters from carbon nanotubes, which exhibited effective elimination of bacterial pathogens ( E. coli and S. aureus ), and Poliovirus sabin-1 from wastewater.

Nanofiltration requires lower operating pressure and lesser energy consumption in comparison of RO and higher rejection of organic compounds compared to UF. Therefore, it can be applied as the tertiary treatment of wastewater (Abdel-Fatah, 2018 ). Apart from nanofilters, there are various kinds of nanoparticles like metal nanoparticles, metal oxide nanoparticles, carbon nanotubes, graphene nanosheets, and polymer-based nanosorbents, which may play a different role in wastewater treatment based on their properties. Kocabas et al. ( 2012 ) analyzed the potential of different metal oxide nanoparticles and observed that nanopowders of TiO 2 , FeO 3 , ZnO 2 , and NiO can exhibit the exceeding amount of removal of arsenate from wastewater. Cadmium contamination in wastewater, which poses a serious health risk, can be overcome by using ZnO nanoparticles (Kumar & Chawla, 2014 ). Latterly, Vélez et al. ( 2016 ) investigated that the 70% removal of mercury from wastewater through iron oxide nanoparticles successfully performed. Sheet et al. ( 2014 ) used graphite oxide nanoparticles for the removal of nickel from wastewater. An exceeding amount of copper causes liver cirrhosis, anemia, liver, and kidney damage, which can be removed by carbon nanotubes, pyromellitic acid dianhydride (PMDA) and phenyl aminomethyl trimethoxysilane (PAMTMS) (Liu et al., 2010 ).

Nanomaterials are efficiently being used for microbial purification from wastewater. Carbon nanotubes (CNTs) are broadly applied for the treatment of wastewater contaminated with E. coli , Salmonella , and a wide range of microorganisms (Akasaka & Watari, 2009 ). In addition, silver nanoparticles reveal very effective results against the microorganisms present in wastewater. Hence, it is extensively being used for microbial elimination from wastewater (Inoue et al., 2002 ). Moreover, CNTs exhibit high binding affinity to bacterial cells and possess magnetic properties (Pan & Xing, 2008 ). Melanta ( 2008 ) confirmed and recommended the applicability of CNTs for the removal of E. coli contamination from wastewater. Mostafaii et al. ( 2017 ) suggested that the ZnO nanoparticles could be the potential antibacterial agent for the removal of total coliform bacteria from municipal wastewater. Apart from the previously mentioned, applicability of the nanotechnology, the related drawbacks and challenges cannot be neglected. Most of the nanoengineered techniques are currently either in research scale or pilot scale performing well (Gehrke et al., 2015 ). Nevertheless, as discussed above, nanotechnology and nanomaterials exhibit exceptional properties for the removal of contaminants and purification of water. Therefore, it can be adapted as the prominent solution for the wastewater treatment (Zekić et al., 2018 ) and further use for drinking purposes.

6.5 Wastewater Treatment by Using Plant Species

Some of the naturally growing plants can be a potential source for wastewater treatment as they remove pollutants and contaminants by utilizing them as a nutrient source (Zimmels et al., 2004 ). Application of plant species in wastewater treatment may be cost-effective, energy-saving, and provides ease of operation. At the same time, it can be used as in situ, where the wastewater is being produced (Vogelmann et al., 2016 ). Nizam et al. ( 2020 ) analyzed the phytoremediation efficiency of five plant species ( Centella asiatica , Ipomoea aquatica , Salvinia molesta , Eichhornia crassipes , and Pistia stratiotes ) and achieved the drastic decrease in the amount of three pollutants viz. total suspended solids (TSS), ammoniacal nitrogen (NH 3 -N), and phosphate levels . All the five species found to be efficient removal of the level of 63.9-98% of NH 3 -N, TSS, and phosphate. Coleman et al. ( 2001 ) examined the physiological effects of domestic wastewater treatment by three common Appalachian plant species: common rush or soft rush ( Juncus effuses L.), gray club-rush ( Scirpus Validus L.), and broadleaf cattail or bulrush ( Typha latifolia L.). They observed in their experiments about 70% of reduction in total suspended solids (TSS) and biochemical oxygen demand (BOD), 50% to 60% of reduction in nitrogen, ammonia, and phosphate levels, and a significant reduction in feacal coliform populations. Whereas, Zamora et al. ( 2019 ) found the removal efficiency of chemical oxygen demand (COD), total solids suspended (TSS), nitrogen as ammonium (N-NH 4 ) and nitrate (N-NO 3 ), and phosphate (P-PO 4 ) up to 20–60% higher using the three ornamental species of plants viz. Canna indica , Cyperus papyrus , and Hedychium coronarium . The list of various plant species applied for the wastewater treatment is shown in Table 3 .

6.6 Wastewater Treatment by Using Microorganisms

There is a diverse group of bacteria like Pseudomonas fluorescens , Pseudomonas putida , and different Bacillus strains, which are capable to use in biological wastewater systems. These bacteria work in the cluster forms as a floc, biofilm, or granule during the wastewater treatment. Furthermore, after the recognition of bacterial exopolysaccharides (EPS) as an efficient adsorption material, it may be applied in a revolutionary manner for the heavy metal elimination (Gupta & Diwan, 2017 ). There are few examples of EPS, which are commercially available, i.e., alginate ( P. aeruginosa , Azotobacter vinelandii ), gellan (Sphingomonas paucimobilis ), hyaluronan ( . aeruginosa , Pasteurella multocida , Streptococci attenuated strains ), xanthan (Xanthomonas campestris ), and galactopol ( Pseudomonas oleovorans ) (Freitas et al., 2009 ; Freitas, Alves, & Reis, 2011a ; Freitas, Alves, Torres, et al., 2011b ). Similarly, Hesnawi et al. ( 2014 ) experimented biodegradation of municipal wastewater using local and commercial bacteria (Sludge Hammer), where they achieved a significant decrease in synthetic wastewater, i.e., 70%, 54%, 52%, 42% for the Sludge Hammer, B. subtilis , B. laterosponus , and P. aeruginosa , respectively. Therefore, based on the above studies, it can be concluded that bioaugmentation of wastewater treatment reactor with selective and mixed strains can ameliorate the treatment. During recent years, microalgae have attracted the attention of researchers as an alternative system, due to their applicability in wastewater treatment. Algae are the unicellular or multicellular photosynthetic microorganism that grows on water surfaces, salt water, or moist soil. They utilize the exceeding amount of nutrients like nitrogen, phosphorus, and carbon for their growth and metabolism process through their anaerobic system. This property of algae also inhibits eutrophication; that is to avoid over-deposit of nutrients in water bodies. During the nutrient digestion process, algae produce oxygen that is constructive for the heterotrophic aerobic bacteria, which may further be utilized to degrade the organic and inorganic pollutants. Kim et al. ( 2014 ) observed a total decrease in the levels of COD (86%), total nitrogen (93%), and total phosphorus (83%) after using algae in the municipal wastewater consortium. Nmaya et al. ( 2017 ) reported the heavy metal removal efficiency of microalga Scenedesmus sp. from contaminated river water in the Melaka River, Malaysia. They observed the effective removal of Zn (97-99%) on the 3 rd and 7 th day of the experiment. The categorized list of microorganisms used for wastewater treatment is presented in Table 4 .

7 The Computational Approach in Wastewater Treatment

7.1 bioinformatics and genome sequencing.

A computational approach is accessible in wastewater treatment. Several tools and techniques are in use such as, sequencing platforms (Hall, 2007 ; Marsh, 2007 ), metagenome sequencing strategies (Schloss & Handelsman, 2005 ; Schmeisser et al., 2007 ; Tringe et al., 2005 ), bioinformatics tools and techniques (Chen & Pachter, 2005 ; Foerstner et al., 2006 ; Raes et al., 2007 ), and the genome analysis of complex microbial communities (Fig. 4 ). Most of the biological database contains microorganisms and taxonomical information. Thus, these can provide extensive details and supports for further utilization in wastewater treatment–related research and development (Siezen & Galardini, 2008 ). Balcom et al. ( 2016 ) explored that the microbial population residing in the plant roots immersed in the wastewater of an ecological WWTP and showed the evidence of the capacity for micro-pollutant biodegradation using whole metagenome sequencing (WMS). Similarly, Kumar et al. ( 2016 ) revealed that bioremediation of highly polluted wastewater from textile dyes by two novel strains were found to highly decolorize Joyfix Red. They were identified as Lysinibacillus sphaericus (KF032717) and Aeromonas hydrophila (KF032718) through 16S rDNA analysis. More recently, Leddy et al. ( 2018 ) reported that research scientists are making strides to advance the safety and application of potable water reuse with metagenomics for water quality analysis. The application of the bio-computational approach has also been implemented in the advancements of wastewater treatment and disease detection.

A schematic showing the overall conceptual framework on which depicting the computational approach in wastewater treatment

7.2 Computational Fluid Dynamics in Wastewater Treatment

In recent years, computational fluid dynamics (CFD), a broadly used method, has been applied to biological wastewater treatment. It has exposed the inner flow state that is the hydraulic condition of a biological reactor (Peng et al., 2014 ). CFD is the application of powerful predictive modeling and simulation tools. It may calculate the multiple interactions between all the water quality and process design parameters. CFD modeling tools have already been widely used in other industries, but their application in the water industry is quite recent. CFD modeling has great applications in water and wastewater treatment, where it mechanically works by using hydrodynamic and mass transfer performance of single or two-phase flow reactors (Do-Quang et al., 1998 ). The level of CFD’s capability varies between different process units. It has a high frequency of application in the areas of final sedimentation, activated sludge basin modeling, disinfection, and greater needs in primary sedimentation and anaerobic digestion (Samstag et al., 2016 ). Now, researchers are enhancing the CFD modeling with a developed 3D model of the anoxic zone to evaluate further hydrodynamic performance (Elshaw et al., 2016 ). The overall conceptual framework and the applications of the computational approach in wastewater treatment are presented in Fig. 4 .

7.3 Computational Artificial Intelligence Approach in Wastewater Treatment

Several studies were obtained by researchers to implement computer-based artificial techniques, which provide fast and rapid automated monitoring of water quality tests such as BOD and COD. Recently, Nourani et al. ( 2018 ) explores the possibility of wastewater treatment plant by using three different kinds of artificial intelligence methods, i.e., feedforward neural network (FFNN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine (SVM). Several measurements were done in terms of effluent to tests BOD, COD, and total nitrogen in the Nicosia wastewater treatment plant (NWWTP) and reported high-performance efficiency of artificial intelligence (Nourani et al., 2018 ).

7.4 Remote sensing and Geographical Information System

Since the implementation of satellite technology, the initiation of new methods and tools became popular nowadays. The futuristic approach of remote sensing and GIS technology plays a crucial role in the identification and locating of the water polluted area through satellite imaginary and spatial data. GIS analysis may provide a quick and reasonable solution to develop atmospheric correction methods. Moreover, it provides a user-friendly environment, which may support complex spatial operations to get the best quality information on water quality parameters through remote sensing (Ramadas & Samantaray, 2018 ).

8 Applications of Treated Wastewater

8.1 scope in crop irrigation.

Several studies have assessed the impact of the reuse of recycled/treated wastewater in major sectors. These are agriculture, landscapes, public parks, golf course irrigation, cooling water for power plants and oil refineries, processing water for mills, plants, toilet flushing, dust control, construction activities, concrete mixing, and artificial lakes (Table 5 ). Although the treated wastewater after secondary treatment is adequate for reuse since the level of heavy metals in the effluent is similar to that in nature (Ayers & Westcot, 1985 ), experimental evidences have been found and evaluated the effects of irrigation with treated wastewater on soil fertility and chemical characteristics, where it has been concluded that secondary treated wastewater can improve soil fertility parameters (Mohammad & Mazahreh, 2003 ). The proposed model (Fig. 3 ) is tested partially previously at a laboratory scale by treating the wastewater (from sewage, sugar, and paper industry) in an ultrasonic bath (Kesari et al., 2011a , b ; Kesari & Behari, 2008 ; Kumar et al., 2010 ). Advancing it with ultraviolet and ozone treatment has modified this in the proposed model. A recent study shows that the treated water passed quality measures suited for crop irrigation (Bhatnagar et al., 2016 ). In Fig. 3 , a model is proposed including all three (UV, US, nanoparticle, and ozone) techniques, which have been tested individually as well as in combination (US and nanoparticle) (Kesari et al., 2011a , b ) to obtain the highest water quality standards acceptable for irrigation and even drinking purposes.

A wastewater-irrigated field is a major source of essential and non-essential metals contaminants such as lead, copper, zinc, boron, cobalt, chromium, arsenic, molybdenum, and manganese. While crops need some of these, the others are non-essential metals, toxic to plants, animals, and humans. Kanwar and Sandha ( 2000 ) reported that heavy metal concentrations in plants grown in wastewater-irrigated soils were significantly higher than in plants grown in the reference soil in their study. Yaqub et al. ( 2012 ) suggest that the use of US is very effective in removing heavy or toxic metals and organic pollutants from industrial wastewater. However, it has been also observed that the metals were removed efficiently, when UV light was combined with ozone (Samarghandi et al., 2007 ). Ozone exposure is a potent method for the removal of metal or toxic compounds from wastewater as also reported earlier (Park et al., 2008 ). Application of US, UV, and O 3 in combination lead to the formation of reactive oxygen species (ROS) that oxidize certain organics, metal ions and kill pathogens. In the process of advanced oxidizing process (AOP) primarily oxidants, electricity, light, catalysts etc. are implied to produce extremely reactive free radicals (such as OH) for the breakdown of organic matters (Oturan & Aaron, 2014 ). Among the other AOPs, ozone oxidization process is more promising and effective for the decomposition of complex organic contaminants (Xu et al., 2020 ). Ozone oxidizes the heavy metal to their higher oxidation state to form metallic oxides or hydroxides in which they generally form limited soluble oxides and gets precipitated, which are easy to be filtered by filtration process. Ozone oxidization found to be efficient for the removal of heavy metals like cadmium, chromium, cobalt, copper, lead, manganese, nickel, and zinc from the water source (Upadhyay & Srivastava, 2005 ). Ultrasonic-treated sludge leads to the disintegration of biological cells and kills bacteria in treated wastewater (Kesari, Kumar, et al., 2011a ; Kesari, Verma, & Behari, 2011b ). This has been found that combined treatment with ultrasound and nanoparticles is more effective (Kesari, Kumar, et al., 2011a ). Ultrasonication has the physical effects of cavitation inactivate and lyse bacteria (Broekman et al., 2010 ). The induced effect of US, US, or ozone may destroy the pathogens and especially during ultrasound irradiation including free-radical attack, hydroxyl radical attack, and physical disruption of cell membranes (Kesari, Kumar, et al., 2011a ; Phull et al., 1997 ; Scherba et al., 1991 ).

8.2 Energy and Economy Management

Municipal wastewater treatment plants play a major role in wastewater sanitation and public health protection. However, domestic wastewater has been considered as a resource or valuable products instead of waste, because it has been playing a significant role in the recovery of energy and resource for the plant-fertilizing nutrients like phosphorus and nitrogen. Use of domestic wastewater is widely accepted for the crop irrigation in agriculture and industrial consumption to avoid the water crisis. It has also been found as a source of energy through the anaerobic conversion of the organic content of wastewater into methane gas. However, most of the wastewater treatment plants are using traditional technology, as anaerobic sludge digestion to treat wastewater, which results in more consumption of energy. Therefore, through these conventional technologies, only a fraction of the energy of wastewater has been captured. In order to solve these issues, the next generation of municipal wastewater treatment plants is approaching total retrieval of the energy potential of water and nutrients, mostly nitrogen and phosphorus. These plants also play an important role in the removal and recovery of emerging pollutants and valuable products of different nature like heavy and radioactive metals, fertilizers hormones, and pharma compounds. Moreover, there are still few possibilities of improvement in wastewater treatment plants to retrieve and reuse of these compounds. There are several methods under development to convert the organic matter into bioenergy such as biohydrogen, biodiesel, bioethanol, and microbial fuel cell. These methods are capable to produce electricity from wastewater but still need an appropriate development. Energy development through wastewater is a great driver to regulate the wastewater energy because it produces 10 times more energy than chemical, thermal, and hydraulic forms. Vermicomposting can be utilized for stabilization of sludge from the wastewater treatment plant. Kesari and Jamal ( 2017 ) have reported the significant, economical, and ecofriendly role of the vermicomposting method for the conversion of solid waste materials into organic fertilizers as presented in Fig. 5 . Solid waste may come from several sources of municipal and industrial sludge, for example, textile industry, paper mill, sugarcane, pulp industry, dairy, and intensively housed livestock. These solid wastes or sewage sludges have been treated successfully by composting and/or vermicomposting (Contreras-Ramos et al., 2005 ; Elvira et al., 1998 ; Fraser-Quick, 2002 ; Ndegwa & Thompson, 2001 ; Sinha et al., 2010 ) Although collection of solid wastes materials from sewage or wastewater and further drying is one of the important concerns, processing of dried municipal sewage sludge (Contreras-Ramos et al., 2005 ) and management (Ayilara et al., 2020 ) for vermicomposting could be possible way of generating organic fertilizers for future research. Vermicomposting of household solid wastes, agriculture wastes, or pulp and sugarcane industry wastes shows greater potential as fertilizer for higher crop yielding (Bhatnagar et al., 2016 ; Kesari & Jamal, 2017 ). The higher amount of solid waste comes from agricultural land and instead of utilizing it, this biomass is processed by burning, which causes severe diseases (Kesari & Jamal, 2017 ). Figure 3 shows the proper utilization of solid waste after removal from wastewater; however, Fig. 5 showing greater possibility in fertilizer conversion which has also been discussed in detail elsewhere (Bhatnagar et al., 2016 ; Nagavallemma et al., 2006 )

Energy production through wastewater (reproduced from Bhatnagar et al., 2016 ; Kesari & Jamal, 2017 )

9 Conclusions and future perspectives

In this paper, we have reviewed environmental and public health issues associated with the use of untreated wastewater in agriculture. We have focused on the current state of affairs concerning the wastewater treatment model and computational approach. Given the dire need for holistic approaches for cultivation, we proposed the ideas to tackle the issues related to wastewater treatment and the reuse potential of the treated water. Water resources are under threat because of the growing population. Increasing generation of wastewater (municipal, industrial, and agricultural) in developing countries especially in India and other Asian countries has the potential to serve as an alternative of freshwater resources for reuse in rice agriculture, provide appropriate treatment, and distribution measures are adopted. Wastewater treatment is one of the big challenges for many countries because increasing levels of undesired or unknown pollutants are very harmful to health as well as environment. Therefore, this review explores the ideas based on current and future research. Wastewater treatment includes very traditional methods by following primary, secondary, and tertiary treatment procedures, but the implementation of advanced techniques is always giving us a big possibility of good water quality. In this paper, we have proposed combined methods for the wastewater treatment, where the concept of the proposed model works on the various types of wastewater effluents. The proposed model not only useful for wastewater treatment but also for the utilization of solid wastes as fertilizer. An appropriate method for the treatment of wastewater and further utilization for drinking water is the main futuristic outcome. It is also highly recommendable to follow the standard methods and available guidelines provided WHO. In this paper, the proposed role of the computational model, i.e., artificial intelligence, fluid dynamics, and GIS, in wastewater treatment could be useful in future studies. In this review, health concerns associated with wastewater irrigation for farmers and irrigated crops consumers have been discussed.

The crisis of freshwater is one of the growing concerns in the twenty-first century. Globaly, about 330 km 3 of municipal wastewater is generated annually (Hernández-Sancho et al., 2015 ). This data provides a better understanding of why the reuse of treated wastewater is important to solve the issues of the water crisis. The use of treated wastewater (industrial or municipal wastewater or Seawater) for irrigation has a better future for the fulfillment of water demand. Currently, in developing countries, farmers are using wastewater directly for irrigation, which may cause several health issues for both farmers and consumers (crops or vegetables). Therefore, it is very imperative to implement standard and advanced methods for wastewater treatment. A local assessment of the environmental and health impacts of wastewater irrigation is required because most of the developed and developing countries are not using the proper guidelines. Therefore, it is highly required to establish concrete policies and practices to encourage safe water reuse to take advantage of all its potential benefits in agriculture and for farmers.

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Acknowledgements

All the authors are highly grateful to the authority of the respective departments and institutions for their support in doing this research. The author VT would like to thank Science & Engineering Research Board, New Delhi, India (Grant #ECR/2017/001809). The Author RS is thankful to the University Grants Commission for the National Fellowship (201819-NFO-2018-19-OBC-UTT-78476).

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Kavindra Kumar Kesari and Ramendra Soni contributed equally to this work.

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Department of Applied Physics, Aalto University, Espoo, Finland

Kavindra Kumar Kesari & Janne Ruokolainen

Department of Molecular and Cellular Engineering, Sam Higginbottom University of Agriculture, Technology and Sciences, Naini, Allahabad, India

Ramendra Soni, Jonathan A. Lal & Vijay Tripathi

Department of Health Informatics, College of Public Health and Health Informatics, Qassim University, Al Bukayriyah, Saudi Arabia

Qazi Mohammad Sajid Jamal

Department of Computational Biology and Bioinformatics, Sam Higginbottom University of Agriculture, Technology and Sciences, Naini, Allahabad, India

Pooja Tripathi

Department of Biotechnology, School of Engineering & Technology, Sharda University, Greater Noida, UP, India

Niraj Kumar Jha

Department of Bioengineering, Faculty of Engineering, Integral University, Lucknow, India

Mohammed Haris Siddiqui

Department of Forestry, NERIST, Nirjuli, Arunachal Pradesh, India

Pradeep Kumar

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Kesari, K.K., Soni, R., Jamal, Q.M.S. et al. Wastewater Treatment and Reuse: a Review of its Applications and Health Implications. Water Air Soil Pollut 232 , 208 (2021). https://doi.org/10.1007/s11270-021-05154-8

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NCERT Class 7 Science Chapter 13 Wastewater Story: Notes and Solutions (Free PDF)

• Updated on  
• Apr 25, 2024

The final chapter of Class 7 Science deals with wastewater and its management. We will begin NCERT Class 7 Science Chapter 13 with the definition of important terms- wastewater, contaminant, and sewage. Thereafter, we will learn about sewage systems and the “Water for Life” campaign of the United Nations. Further, we will walk through the wastewater treatment process in a wastewater treatment plant. Also, we learn about sanitation and tips to dispose of waste effectively at home. Let us explore all these elements in our CBSE notes. Let us begin!!

Download NCERT Solutions Class 7 Science Chapter 13 Important Questions and Answers PDF

Explore all the Chapters of Class 7 Science: 

Also Read: Essay on Water Pollution: Samples in 200, 500 Words

Table of Contents

• 1.1 What is Wastewater?
• 1.2 Contaminant
• 1.3 What is Sewage?
• 1.4 Sewage Systems
• 1.5 Sewage Treatment
• 1.6 Water for Life
• 2.1 What is Wastewater Treatment?
• 2.2.1 Wastewater Collection
• 2.2.2 Screening
• 2.2.3 Removal of Organic Waste or Primary Treatment
• 2.2.4 Aeration or Secondary Treatment 
• 2.2.5 Filtration
• 3 Household Practices to Minimise or Eliminate Water Pollution
• 4 Sanitation and Disease
• 5.1 Septic Tanks
• 5.2 On-Site Human Disposal
• 6 NCERT Solutions Class 7 Science Chapter 13: Wastewater Story

Introduction to Class 7 Science Chapter 13: Wastewater Story

In Class 7 Science Chapter 13 we begin with the definition of wastewater and water cleaning process. Also, we will explore the “Water for Life” campaign of the United Nations Organisation. 

What is Wastewater?

Abundant foam, combined with oil, the dark-brown liquid that flows away through pipes from sinks, showers, toilets, and washing machines is considered unclean liquid. This liquid is known as wastewater.

Contaminant

A contaminant is a substance or agent that pollutes or degrades the quality of another substance, such as water or food.

What is Sewage?

Sewage comprises wastewater discharged from residential areas, industrial facilities, hospitals, offices, and various other sources. It also includes rainwater that flows along streets during storms or heavy rain. This runoff from roads and rooftops often carries impure substances. 

Thus, “sewage” is a liquid waste, which primarily contains water with dissolved and suspended impurities.

Sewage Systems

Sewage from each house is gathered via the drainage system. It is then transported to wastewater treatment plants through a network of pipes known as “sewers”. After treatment, the wastewater is released into natural water bodies.

Sewage Treatment

The purification of water involves eliminating contaminants before it is discharged into a body of water or recycled. This procedure for treating wastewater is commonly known as sewage treatment.

Water for Life

Before we dive into the “Water for Life” initiative by the UNO, let us learn about the reasons for global water scarcity. 

Here are some common reasons for the increasing scarcity of freshwater

• Population growth
• Industrial development
• Mismanagement, and other elements. 

Recognising the pressing nature of this issue, the United Nations General Assembly (UNGA) declared March 22, 2005, as World Water Day . Furthermore, the UNGA designated the period from 2005 to 2015 as the International Decade for Action on “Water for Life.” The primary objective during this decade was to halve the number of people lacking access to safe drinking water. Although there has been noticeable progress toward this goal, there is still much work to be done.

Read More: Class 8 Pollution of Air and Water: Notes and PDF

Wastewater Treatment

In this part of NCERT Class 7 Science Chapter 13, we will learn about the different stages of wastewater treatment in a wastewater treatment plant (WWTP). 

What is Wastewater Treatment?

The process of removing impurities from polluted water to make it usable is known as wastewater treatment. This process includes a combination of physical, chemical, and biological processes designed to eliminate physical, chemical, and biological impurities that are present in the wastewater.

Stages of Wastewater Treatment

Here are the different stages of wastewater treatment:

Wastewater Collection

Firstly, wastewater is collected from different sources in large containers. The water is collected through pipes connecting houses, factories, and other production facilities. 

Thereafter, screening of wastewater takes place. In this process, large substances are separated from wastewater. After this, the large objects are transferred to the sand and grit removal tank. 

Removal of Organic Waste or Primary Treatment

After the initial screening process, wastewater undergoes primary treatment, during which all organic waste is eliminated. This primary treatment involves directing the wastewater into large tanks where solid materials settle at the top surface of the tanks.

The solids that settle after the primary treatment are called “sludge”. After the collection of sludge, it is decomposed using bacteria. In this process of decomposition, a gas is produced. The gas produced in this process is known as “biogas”. Furthermore, biogas can serve as a fuel source or be used for electricity generation.

Aeration or Secondary Treatment 

Following the primary treatment, the water is directed through a tank known as an “aeration lane” where air is introduced into the water to promote the growth of aerobic bacteria. These bacteria are responsible for breaking down small particles of sludge that may have escaped during the primary treatment process.

Following the secondary treatment, the decomposed sludge settles at the bottom of a large tank known as the “activated sludge” tank, and it contains air within it.

Finally, the activated sludge is transferred through a sand-drying machine to remove moisture and separate the water from it. The water is then allowed to flow over a wall, where it is filtered through a sand bed to eliminate any remaining particles. The purified water is subsequently discharged into the river.

Also Read: What are Different Types of Water Pollution?

Household Practices to Minimise or Eliminate Water Pollution

Moreover, NCERT Class 7 Science Chapter 13 also gives ideas to reduce or eliminate water pollution in our houses. Let us pledge to practice these in our daily lives.

• Do not dispose of cooking oil and fats down the drain as they can block pipes. Also, oil and fats reduce the effectiveness of soil in filtering water. Instead, throw them in the dustbin.
• Similarly, chemicals like paints, solvents, insecticides, motor oil, and medicines should not be poured down the drain, as they can harm the microbes responsible for purifying water. Properly dispose of these chemicals following recommended guidelines to protect the water treatment process.
• Also, dispose of used tea leaves, leftover food, soft toys, cotton products, sanitary towels, and similar items in the trash. This is because, these types of waste can block drains, restrict the flow of oxygen, and hinder the decomposition process.

Related Reads:

Sanitation and Disease

Sanitation typically involves offering facilities and services for the safe disposal of human urine and faeces. Inadequate sanitation causes numerous diseases and health risks.

As a large population in developing countries like India and Pakistan and underdeveloped nations like Syria and Palestine consume polluted water, they are often affected by the following water-borne diseases:

Also Read: Water Image Questions & Tips to Crack them

Alternative Arrangement for Sewage Disposal

In efforts to improve sanitation, the promotion of affordable on-site sewage disposal systems is underway. Some examples include septic tanks, compositing pits, and chemical toilets.

Septic Tanks

A septic tank is an underground, watertight container typically constructed from concrete or polyethene. It is designed to collect sewage and facilitate its decomposition through bacterial processes before allowing the treated effluent to drain through a soak-away system.

On-Site Human Disposal

Certain organizations provide hygienic on-site human waste disposal technology in the form of toilets that do not necessitate manual scavenging. Excreta from these toilets flows through covered drains into a biogas plant, where the produced biogas serves as an energy source.

Read More: Essay on Water Conservation

Explore all the Chapters of Class 7 Science: 

NCERT Solutions Class 7 Science Chapter 13: Wastewater Story

In the final section of Class 7 Science Chapter 13, we have tried to answer all the questions. All solutions adhere to the latest CBSE curriculum. 

Ques 1. Fill in the blanks:

a. Cleaning of water is a process of removing_______________.

b. Wastewater released by houses is called________________.

c. Dried______________ is used as manure.

d. Drains get blocked by_(1)____________ and_(2)____________.

a. Pollutant

b. Sewage 

d. (1) Cooking oil; (2) fats

Ques 2. What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Ans: Sewage” is a liquid waste, which primarily contains water with dissolved and suspended impurities.

The discharge of untreated sewage into rivers and seas will contaminate the water in these water bodies. Further, the consumption of polluted water by humans, terrestrial animals and aquatic animals will cause several diseases in these organisms. 

Ques 3. Why should oils and fats be not released in the drain? Explain.

Ans: Do not dispose of cooking oil and fats down the drain as they can block pipes. Also, oil and fats reduce the effectiveness of soil in filtering water.

Ques 4. Describe the steps involved in getting clarified water from wastewater.

Ans: Here are the steps to get clarified water from wastewater:

• To improve the quality of the wastewater, you can use an aquarium aerator to bubble air through the sample in a glass jar. 
• For effective aeration, you must leave the aerator attached overnight, although several hours can also be effective. Alternatively, you can also use a mechanical stirrer or mixer to reduce the unpleasant odour of the wastewater.
• Following aeration, the water undergoes filtration through layers of sand, fine gravel, and medium gravel. This filtration process effectively removes various types of pollutants, and it is continued until the water becomes clear.
• Finally, water disinfection is achieved by employing a chlorine tablet.

Ques 5. What is sludge? Explain how it is treated.

Ans: The solids that settle after the primary treatment are called “sludge”. 

After the collection of sludge, it is decomposed using bacteria. In this process of decomposition, a gas is produced. 

Ques 6. Untreated human excreta is a health hazard. Explain.

Ans: Untreated human excreta is a significant health hazard due to the presence of several disease-causing microorganisms and pollutants. These contaminants can pollute the soil and water resources that people rely on for drinking and domestic purposes. When we use water that has been contaminated with human excreta, they are at risk of contracting diseases such as Cholera, Typhoid, Dysentery, and Hepatitis.

Ques 7. Name two chemicals used to disinfect water.

Ans: Ozone and Chlorine

Ques 8. Explain the function of bar screens in a wastewater treatment plant.

Ans: Bar screens are designed to separate large objects such as napkins, rags, cans, sticks, and plastic pouches from the wastewater.

Ques 9. Explain the relationship between sanitation and disease.

Ans: Sanitation typically involves offering facilities and services for the safe disposal of human urine and faeces. Inadequate sanitation causes numerous diseases and health risks as we consume water that is discharged from sewage systems. 

Inefficient sanitation causes the following waterborne diseases:

• Dysentery 

Ques 10. Outline your role as an active citizen in relation to sanitation.

Ans:  As an active citizen, I must contribute to the sanitation process in the following ways:

• I will keep my surroundings clean.
• I will manage my household sanitation system properly.
• I will dispose of waste properly and after segregation.
• I will report to the concerned authorities about leakages in the sewage system in my neighbourhood. 

Ques 11. Here is a crossword puzzle: Good luck!

3. Liquid waste products

4. Solid waste extracted in sewage treatment

6. A word related to hygiene

8. Waste matter discharged from the human body

1. Used water

2. A pipe carrying sewage

5. Micro-organisms which cause cholera

7. A chemical to disinfect water

6. Sanitation

1. Wastewater

5. Bacteria

Ques 12. Study the following statements about ozone:

a. It is essential for breathing of living organisms.

b. It is used to disinfect water.

c. It absorbs ultraviolet rays.

d. Its proportion in air is about 3%.

Which of these statements are correct?

(i) a, b, and c

(ii) b and c

(iii) a and d

(iv) All four

Ans: Option (ii) b and c

Also Read: How to Prepare for UPSC in 6 Months?

Ans: Following the secondary treatment in wastewater treatment plants, the decomposed sludge settles at the bottom of a large tank known as the “activated sludge” tank, and it contains air within it.

Ans: Abundant foam, combined with oil, the dark-brown liquid that flows away through pipes from sinks, showers, toilets, and washing machines is considered unclean liquid. This liquid is known as wastewater.

Ans: A contaminant is a substance or agent that pollutes or degrades the quality of another substance, such as water or food.

Follow Leverage Edu for complete study material on CBSE Notes Class 7 Science . 

Ankita Singh

Ankita is a history enthusiast with a few years of experience in academic writing. Her love for literature and history helps her curate engaging and informative content for education blog. When not writing, she finds peace in analysing historical and political anectodes.

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NCERT Class 7 Notes Science Chapter 18 Waste Water Story

NCERT Class 7 Science Notes Chapter 18 Waste Water Story

Water is an elixir of life. We all use water and in that process of using, we make it dirty. The water rich in a lather, mixed with oil and other pollutants that go down the drains from sinks, showers, toilets, laundries is dirty. It is called wastewater.

We use water every day for drinking, bathing, washing clothes, cooking food, washing utensils, flushing toilets, mopping the floors, etc. We cannot think of our life without water. We use lots of water daily which is passed on to the drainage system every day.

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Water, Our Lifeline Water is needed by all forms of life. Clean water is a basic need of human beings. Unfortunately, clean water is not available to a large segment of human populations.

The water which is unfit for human consumption becomes the source of many water-borne diseases which ultimately lead to loss ( of human life. It is estimated that one billion human beings do not get safe drinking water. So, realising the urgency we celebrate 22nd March as World Water Day to bring awareness amongst people for safe water, fit for human consumption. Thus, the water is cleaned by removing pollutants before it enters a waterbody or is reused. This process of wastewater treatment is commonly known as sewage treatment which takes place in several steps as discussed later.

On the World Water Day, i.e. 22 March 2005, the General Assembly of the United Nations proclaimed the period 2005-2015 as the International Decade for action on Water for Life. All efforts made during this decade aim to reduce by half the number of people who do not have access to safe drinking water.

Sewage It is wastewater released by homes, industries agricultural fields and other human activities. It also includes rainwater that has run down the street during a storm or heavy rain and it is liquid waste. Most of its water has dissolved and suspended impurities called contaminants.

Also Read: NCERT Exemplar Solutions Class 7 Science Solutions Chapter 18 Wastewater Story

Composition of Sewage The following components make the sewage:

• The organic impurities present in sewage are human faeces, animal wastes (like animal dung), urea (as urine), oil, fruits and vegetable wastes, pesticides, herbicides, etc.
• The inorganic impurities present in sewage are nitrates, phosphates and metals.
• The nutrients present in sewage are nitrogen and phosphorus.
• The bacteria present in sewage include those bacteria which cause water-borne diseases such as cholera and typhoid.
• The other microbes present in sewage are Protozoa which cause a water-borne disease called dysentery.

Water Freshens Up: An Eventful Journey In a house (a public building) generally, there are two sets of pipes, i.e. one set of pipes brings clean drinking water into the house and the other set of pipes takes away wastewater (sewage) from houses. For proper sanitation, a well-maintained sewage system is required.

Sewerage System The pipes which carry away wastewater or sewage from houses and other buildings are buried under the ground. An underground pipe which carries away dirty drainage water and waste matter is called sewer. The provision of drainage at a place by laying sewers under the ground is called sewerage. Actually, sewerage is an underground network of interconnected pipes called sewers that carries the sewage from the place where it is produced to the sewage treatment plants, where it is processed.

Manholes A manhole is a covered vertical hole in the ground, pavement or road, above the underground sewer pipeline through which a worker can go down up to the sewer pipes for inspection, cleaning, etc. Manholes are provided at every 50-60 m distance in the main sewer pipeline. Manholes are also provided at the junction of two or more sewers and at points where there is a change in the direction of the sewer line.

Treatment of Polluted Water Perform the following activity. It will help you to understand the processes that take place at the wastewater treatment plant.

Wastewater Treatment Plant (WWTP) A place where wastewater or sewage from houses and other buildings is brought for processing is called wastewater treatment plant. Treatment of wastewater involves physical, biological and chemical processes depending on the nature of contaminants.

2. Biological Process The first sedimentation tank is sloped towards the centre. Solid like faeces settle at the bottom and is called sludge which is removed by a scraper. Oils and grease float at the surface of the water are removed by a skimmer. The biogas produced (by anaerobic bacteria) in the process can be used as fuel or can be used to produce electricity. Here, water gets cleared of rubbage, oil, grease, etc and we get clarified water which is sent to aeration tank now. In the aeration tank, the watery waste already contains bacteria (aerobic) in it. The compressed air bubbles are passed through this waste to provide 02 to the bacteria to increase bacterial activity which ultimately digests human waste, food waste, soaps and other unwanted and harmful matter still remaining in the wastewater leaving behind fairly pure water.

3. Chemical Process The water after aeration tank is allowed to stand in a second sedimentation tank. Here, the microbes present get settled at the bottom at the tank in the form of activated sludge which is about 97% water. At this stage, water has very low level of organic matter suspended matter and does not contain many harmful things. It is safe for human consumption but is disinfected by chlorine or ozone before distributing it.

Become an Active Citizen Waste generation is a natural part of human activity but we can limit the type of waste and quantity of waste produced. Often we have been repelled by an offensive smell. The sight of open drains is disgusting. The situation worsens in the rainy season when the drains start overflowing. We have to wade through the mud pools on the roads. Most unhygienic and unsanitary conditions prevail. Flies, mosquitoes and other insects breed in it.

We should be an enlightened citizen and approach the municipality or the gram panchayat. We should also insist that open drains should be covered. If the sewage of any particular house makes the neighbourhood dirty. We should request them to be more considerate about other’s health.

Note: We should plant Eucalyptus trees all along sewage ponds. These trees absorb all surplus wastewater rapidly and release pure water vapour into the atmosphere. (NCERT Class 7 Notes Science Chapter 18)

Better House Keeping Practices We must minimise and manage waste at our houses before its disposal in the following manner:

• Cooking oil and fats should not be thrown down the drain. They can harden and block the pipes. In an open drain, the fats clog the soil pores reducing its effectiveness in filtering water. Throw oil and fats in the dustbin.
• Used tea leaves, solid food remains, soft toys, cotton, sanitary towels, etc., should also be thrown in the dustbin. These wastes choke the drains. They do not allow the free flow of oxygen. This hampers the degradation process.
• The chemicals like paints, solvents, insecticides, medicines and motor oils should not be thrown in drains as they kill helpful microbes which digest the organic waste.

Sanitation and Disease Contaminated water and poor sanitation practices are the major causes of the number of infectious diseases in our country. Safe sewage disposal facilities are still not available at many cities and villages in India. So, people go to open places and defecate. This causes the increase in insect-vector population which transmit diseases like cholera, typhoid, meningitis, etc.

Untreated human excreta is a health hazard which causes soil pollution and water pollution also. The river water and groundwater are sources of water for drinking for many people. So, the contaminated water can spread many diseases especially water-borne.

Vermi-processing Toilets In the vermi-processing toilets, human excreta is treated by earthworms in a pit. The earthworms usually eat up all organic matter present in human excrete and turn it into compost. These are tow water use toilets for the safe processing of human.

Alternate Arrangement for Sewage Disposal Low cost outside the sewage disposal system has been developed to take care of places where there is no sewage system, e.g. rural areas, isolated buildings. These are described below: (i) Septic tanks: Septic tank is a low-cost onsite sewage disposal system. Septic tanks are suitable where there is no sewerage made. These tanks need cleaning every four to six months.

A septic tank usually consists of a big, covered underground tank made of concrete having an inlet pipe at one end and on outlet pipe at the other end. The toilet seat is connected to the inlet pipe of the septic tank. The human excreta from the toilet seat enters into the septic tank through the inlet pipe. The solid part of excreta keeps on collecting at the bottom of the septic tank in the form of a sludge whereas watery waste remains above it.

The anaerobic bacteria breakdown most of the solid organic matter present in human excreta due to which the volume of solid waste is reduced too much. The digested solid waste keeps on depositing at the bottom of septic tank. The watery waste is also cleaned by anaerobic bacteria. The excess water goes out of the septic tank through the outlet pipe and get absorbed in soil.

(ii) Composting pits: These are self-sustained human waste disposal units which is not connected to a sewer line or a septic tank. A composting toilet breaks down and dehydrates human waste to compost.

(iii) Chemical toilets: These toilets have limited storage capacity for human waste and need to be emptied periodically. These are the toilets which use chemically treated reservoir located just below the toilet seats. The chemicals reduce the foul smell coming out of human excrete and carry out partial disinfection of human waste.

Sanitation at Public Places In our country, fairs are organised periodically. A large number of people participate in them. In the same way, railway stations, bus depots, airports, hospitals are very busy places. Thousands of people visit them daily which generate large amount of waste. It must be disposed of properly otherwise epidemics could break out. The government has laid down certain standards of sanitation but unfortunately, they are not strictly enforced. We should not scatter litter anywhere. If there is no dustbin in sight, we should carry the litter at home and throw it in the dustbin.

Conclusion We all have a role to play in keeping our environment clean and healthy. We must realise our responsibility in maintaining the water sources in a healthy state. Adopting good sanitation practices should be our way of life. As an agent of change your individual initiative will make a great difference. Influence others with your energy ideas and optimum, A lot con be done if people work together. There is great power in collective action. As an active citizen, we have many responsibilities regarding sanitation. These can be listed as follows:

• To ensure that our surroundings are clean.
• To ensure that the sewerage system in our house is properly managed.
• If any leakage or an open drain in the sewerage system is present, then it should be reported to the municipality or the gram panchayats to insist that the open drain must be covered properly and several air and water-borne diseases can be prevented.

Note: Mahatma Gandhi said, ‘No one needs to wait for anyone else to adopt a humane and enlightened course of action’.

We hope the given NCERT Class 7 Notes Science Chapter 18 Waste Water Story Pdf free download will help you. If you have any query regarding CBSE Class 7 Science Notes Chapter 18 Waste Water Story, drop a comment below and we will get back to you at the earliest.

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NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12

NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story

September 25, 2019 by Sastry CBSE

Topics and Sub Topics in Class 7 Science Chapter 18 Wastewater Story:

Q.1. Fill in the blanks: (a) Cleaning of water is process of removing __________ (b) Wastewater released by houses is called __________. (c) Dried __________ is used as manure. (d) Drains get blocked by __________ and __________. Ans .(a) pollutants (b) sewage (c) sludge (d) (d) chemicals, kitchen waste

Q.2. What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas. Ans . Sewage is a liquid containing wastes which is disposed by households, industrial and agricultural activities in water. It is harmful to discharge untreated sewage into rivers or seas because it can pollute the whole sources of water. Sewage contains harmful substances and disease causing organisms. It is therefore dangerous to release untreated sewage in water.

Q.3. Why should oils and fats be not released in the drain? Explain. Ans . Oils and fats should not be released in drains because they harden the soil in the pipes and block them. Fats get clogged in holes of the soil in the drain and block it. It does not allow the water to flow.

Q.4. Describe the steps involved in getting clarified water from wastewater. Ans. Following steps are involved in the purification of water: (i) Firstly all the physical impurities like stones, plastic bags, cans etc. are to be removed. It is done by passing the water through bar screens. (ii) Then water is taken to grit and sand removal tank where impurities are removed by sedimentation. (iii) Solid impurities and feaces etc. are collected from bottom of water. These impurities collected are called sludge. (iv) Clarified water is cleaned of other impurities by aerator. All disease causing bacteria are removed by chlorination.

Q.5. What is sludge? Explain how it is treated. Ans . Sludge is the collected solid waste from the wastewater during the treatment in water treatment plant. Sludge is decomposed in a separate tank by the anaerobic bacteria. Activated sludge is used as manure.

Q.6. Untreated human excreta is a health hazard. Explain. Ans. Untreated human excreta can cause a lot of health related problems. It pollutes water, air and soil. The polluted water contain disease causing bacteria which can spread epidemics like cholera, meningitis etc.

Q.7. Name two chemicals used to disinfect water. Ans. Chlorine and ozone

Q.8. Explain the Junction of bar screens in a wastewater treatment plant. Ans . Bar screens clear the wastewater of all the physical impurities. Large size waste like napkins, plastics, cans etc. are removed from the wastewater through the bar screens.

Q.9. Explain the relationship between sanitation and disease. Ans . Sanitation and disease are related to each other. Sanitation involves proper disposal of sewage and refuse from hou&e and public places. If sanitation is there, no disease will occur, but if sanitation is not there various types of disease will occur and spread. So sanitation should be kept to avoid disease.

Q.10. Outline your role as an active citizen in relation to sanitation. Ans . As active citizen we should take care of our personal environmental sanitation. We should make people aware of the benefits of sanitation. We should help municipal corporations to cover all the open drains and remove disease causing substances thrown in open.

Q.12. Study the following statements about ozone: (a) It is essential for breathing of living organisms. (b) It is used to disinfect water. (c) It absorbs ultraviolet rays. (d) Its proportion in air is about 3%. Which of these statements are correct? (i) (a), (b) and (c) (ii) (b) and (c) (iii) (a) and (d) (iv) All four Ans. (ii) (b) and (c)

NCERT Solutions for Class 7 Science – All Chapters

• Chapter 1 Nutrition in Plants
• Chapter 2 Nutrition in Animals
• Chapter 3 Fibre to Fabric
• Chapter 4 Heat
• Chapter 5 Acids, Bases and Salts
• Chapter 6 Physical and Chemical Changes
• Chapter 7 Weather, Climate and Adaptations of Animals to Climate
• Chapter 8 Winds, Storms and Cyclones
• Chapter 9 Soil
• Chapter 10 Respiration in Organisms
• Chapter 11 Transportation in Animals and Plants
• Chapter 12 Reproduction in Plants
• Chapter 13 Motion and Time
• Chapter 14 Electric Current and Its Effects
• Chapter 15 Light
• Chapter 16 Water: A Precious Resource
• Chapter 17 Forests: Our Lifeline
• Chapter 18 Wastewater Story

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NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story

* According to the CBSE Syllabus 2023-24, this chapter has been renumbered as Chapter 13.

The NCERT Solutions Class 7 Science Chapter 18 – Wastewater Story is crucial for the students of the 7th standard. The solutions are provided here to assist the students in understanding the Wastewater Story in an easy and interesting way. All the NCERT Solutions are prepared and compiled by subject experts as per the latest CBSE syllabus (2023-2024). It is important for the students to practise the solutions regularly for effective preparation for the examination.

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Exercise Questions

1. Fill in the blanks:

(a) Cleaning of water is a process of removing ____________.

(b) Wastewater released by houses is called ____________.

(c) Dried ____________ is used as manure.

(d) Drains get blocked by ____________ and ____________.

(a) Cleaning of water is a process of removing pollutants .

(b) Wastewater released by houses is called sewage .

(c) Dried sludge is used as manure.

(d) Drains get blocked by cooking oil and fats .

2. What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Wastewater released by houses is called sewage . Untreated sewage should not be discharged into the sea because sewage consists of pollutants and harmful microorganisms, which will contaminate water, causing disease in people using contaminated water.

3. Why should oils and fats not be released in the drain? Explain.

Oils and fats should not be released into the drain because drains get blocked by cooking oil and fats.

4. Describe the steps involved in getting clarified water from wastewater.

Use an aerator from an aquarium to bubble air through the sample in the glass jar. Allow several hours for aeration; leave the aerator attached overnight. If you do not have an aerator, use a mechanical stirrer or a mixer. This reduces the foul smell of wastewater.

Then, the water is filtered through the layers of sand, fine gravel and medium gravel. Filtration makes the wastewater clean from various types of pollutants. The water is filtered continuously until it becomes clear.

Water is disinfected by using a chlorine tablet.

5. What is sludge? Explain how it is treated.

Solids like faeces settle at the bottom while treating sewage, and this material is called sludge. Sludge can be treated as follows:

Sludge is removed using a skimmer and then transferred to a tank where it is decomposed by anaerobic bacteria to produce biogas.

6. Untreated human excreta is a health hazard. Explain.

Untreated human excreta is a health hazard because it consists of various disease-causing microorganisms and pollutants that will contaminate the soil and water resource from where people draw water for drinking and domestic purposes. When people use water contaminated with human excreta, they get diseases like Cholera, Typhoid, Dysentry and Hepatitis.

7. Name two chemicals used to disinfect water.

Chlorine and Ozone are used to disinfect water.

8. Explain the function of bar screens in a wastewater treatment plant.

Bar screens remove large objects like rags, sticks, cans, plastic packets and napkins.

9. Explain the relationship between sanitation and disease.

Sanitation and disease are interrelated as lack of sanitation leads to illness, and good sanitation practices prevent diseases.

10. Outline your role as an active citizen in relation to sanitation.

Every citizen has a role to play in maintaining proper sanitisation. Following are the things we should follow to play an active role.

• Ensure that our surroundings are kept clean.
• The sewage system in the house should be properly managed
• Report to the concerned authorities immediately in case of leakages in sewage pipes.

11. Here is a crossword puzzle: Good luck!

3. Liquid waste products

4. Solid waste extracted in sewage treatment

6. A word related to hygiene

8. Waste matter discharged from human body

1. Used water

2. A pipe carrying sewage

5. Micro-organisms which causes cholera

7. A chemical to disinfect water

6. Sanitation

1. Wastewater

5. Bacteria

(a) It is essential for breathing of living organisms.

(b) It is used to disinfect water.

(c) It absorbs ultraviolet rays.

(d) Its proportion in air is about 3%. Which of these statements are correct?

(i) (a), (b) and (c)

(ii) (b) and (c)

(iii) (a) and (d)

(iv) All four

The answer is (ii) (b) and (c)

Introduction to NCERT Solutions Class 7 Science Chapter 18 Wastewater Story

This chapter specifically deals with the issue of contaminants in water. Water is an important resource not just for humans but for all the organisms on earth. Therefore, contaminating this natural resource has dire consequences. The main reasons for water pollution are our commercial and industrial activities. All the waste effluents that reach water bodies results in water pollution. In the long run, this can cause many diseases and health hazards for us.

For instance, in Minamata City, Japan, mercury runoff from a factory polluted the waters, and the poisoning went undetected for decades. It came to notice only when the people saw their newborns had birth defects. It was found that the mercury runoff had contaminated the marine ecosystem, resulting in fish species ingesting the mercury. Over a period of time, mercury accumulation in fish species got transferred into humans who consumed contaminated fish. This adversely affected bodily functions and caused a lot of problems for the people and their descendants. Hence, we need to take care of such issues by preventing industrial effluents which pollute our most precious resource – water.

Topics Covered in NCERT Solution for Class 7 Science Chapter 18 Wastewater Story:

Wastewater Story Chapter has 8 subtopics which are listed below.

• Water our lifeline
• What is sewage
• Water freshens up-an eventful journey
• Wastewater treatment plant
• Better housekeeping practices
• Sanitation and diseases
• An alternative arrangement for sewage disposal
• Sanitation at public places

Water is a resource that we use for almost all of our activities. Consequently, polluting this resource can adversely affect our health. It is mainly polluted by human activities as a result of commercial or industrial exploits. The waste by-products contain many poisonous chemicals that disrupt the marine ecosystem. Also, human excreta poses a major threat and could potentially be a bio-hazard due to many harmful microbes it carries. These microbes or chemicals could leech into the aquatic environment affecting every life form that comes in contact with it.

NCERT Solutions Class 7 Wastewater Story guides the students to segregate waste in a way to reduce water pollution. This chapter demonstrates the importance of water in balancing the ecosystem. Students will get to study the meaning of sewage, its treatment and disposal methods. This chapter creates an awareness of sanitation in students, which helps them to become responsible citizens.

Check here to refer to the other NCERT solutions for Class 7 Science Chapters .

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NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story

NCERT Solutions for CBSE Class 7 Science Chapter 18 Wastewater Story are given below. These solutions help students to clear their doubts and to obtain good marks in final exam. Class 7 Science NCERT questions and answers provided in this article are strictly based on the CBSE syllabus and curriculum.

Class 7 Science Chapter 18 Wastewater Story NCERT Solutions

Class 7 NCERT Solutions for Science Chapter 18 includes all the intext and exercise questions. All these questions are solved by experts with a detailed explanation that will help students complete their assignments and homework.

Question 1: Fill in the blanks:

(a) Cleaning of water is process of removing __________ (b) Wastewater released by houses is called __________. (c) Dried __________ is used as manure. (d) Drains get blocked by __________ and __________.

Answer: (a) Cleaning of water is a process of removing pollutants.

(b) Wastewater released by houses is called sewage.

(c) Dried sludge is used as manure.

(d) Drains get blocked by oils and fats.

Question 2: What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Answer: Sewage is the wastewater containing both liquid and solid wastes produced by human activities from homes, industries, hospitals, offices, etc.

Sewage contains various contaminants including disease-causing bacteria and other microbes. If untreated sewage is discharged into rivers or seas, then the water in the rivers or seas would also get contaminated. If this contaminated water is used for drinking, then it can cause diseases such as cholera, typhoid, dysentery, etc. which may lead to death. That is why it is harmful to discharge untreated sewage into rivers or seas.

Question 3: Why should oils and fats be not released in the drain? Explain.

Answer: Oil and fats can clog the drains reducing its effectiveness in filtering water. In open drains, they block the pores in the soil and thus hamper the filtration by soil. Hence, oil and fats should not be released in the drain.

Question 4: Describe the steps involved in getting clarified water from wastewater.

Answer: The steps involved in getting clarified water from wastewater are as follows:

(i) Use an aerator to bubble air through the wastewater. A mechanical stirrer or a mixer can also be used in place of the aerator. This helps in reducing bad odour of the wastewater.

(ii) Then, the water is filtered through the layers of sand, fine gravel, and medium gravel. Filtration makes the wastewater clean from various types of pollutants. The water is filtered continuously until it becomes clear.

(iii) Then any disinfectant such as chlorine tablet is added to the filtrate and stirred to obtain completely clear water.

Question 5: What is sludge? Explain how it is treated.

Answer: Sludge is human waste (like faeces) in waste water left during sewage treatment. Since it is organic waste, it is used to produce bio gas and manure.

Sludge is collected by a scrapper. It is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel. After the aerator tank, microbes and human waste settle down and form activated sludge. The activated sludge is about 97% water. The water is removed by sand drying beds or machines. Dried sludge is used as manure, returning organic matter and nutrients to the soil.

Question 6: Untreated human excreta is a health hazard. Explain.

Answer: Untreated human excretions are a health hazard. It causes pollution of soil and water including the underground water. Thus, it contaminates the sources of water from which people collect water for drinking and household purposes. When this contaminated water is used for drinking, it can cause diseases such as cholera, typhoid, hepatitis, dysentery, etc., which may even lead to death.

Question 7: Name two chemicals used to disinfect water.

Answer: Chemicals like chlorine (Chlorine dioxide) and ozone (in the pharmaceutical industry) are commonly used to disinfect water.

Question 8: Explain the function of bar screens in a wastewater treatment plant.

Answer: Bar screens clear the wastewater of all the physical impurities. Large size waste like napkins, plastics, cans etc. are removed from the wastewater through the bar screens.

Question 9: Explain the relationship between sanitation and disease.

Answer: Sanitation and disease are related to each other. Sanitation involves proper disposal of sewage and refuse from house and public places. If sanitation is there, no disease will occur, but if sanitation is not there various types of disease will occur and spread. So sanitation should be kept to avoid disease.

Question 10: Outline your role as an active citizen in relation to sanitation.

Answer:  A citizen has many responsibilities regarding sanitation. Among other things, an active citizen should do the following with regard to maintaining proper sanitation:

(i) Ensure that his surroundings (both inside and outside home) are clean.

(ii) Ensure that the sewerage system in his house is properly managed.

(iii) If he notices some leakage or other problem in the sewerage system, he should report it to the municipality.

Question 11: Here is a crossword puzzle: Good luck!

Across 3. Liquid waste products 4. Solid waste extracted in sewage treatment 6. A word related to hygiene 8. Waste matter discharged from human body

Down 1. Used water 2. A pipe carrying sewage 5. Micro-organisms which causes cholera 7. A chemical to disinfect water

Question 12: Study the following statements about ozone:

(a) It is essential for breathing of living organisms. (b) It is used to disinfect water. (c) It absorbs ultraviolet rays. (d) Its proportion in air is about 3%.

Which of these statements are correct?

(i) (a), (b) and (c) (ii) (b) and (c) (iii) (a) and (d) (iv) All four

Answer: (ii) (b) and (c)

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Short Story On Save Water Save Life

“Water is one of the important elements which we need for surviving. Water is very precious to our life. We should conserve water and spread awareness on conservation of water.” - these are things which we have read and heard innumerable times, but do we really understand the urgency of the ‘water saving’ quotes? Let us give a reality check. 

Horrifying Data on Water and Life!

On average, a human body requires 3.7 litres of water per day. At present, on Earth, approximately there are 775.28 crores of people drinking water every day, which means on average, 2868.536 crores litres of water are required per day to stay alive in this mortal world! Now, do you know what is the water constituent of the Earth? It is only 3%! Nearly about 65% of drinking water is stuck in glaciers, while only 1% of potable water is present in rivers, lakes, and other water bodies. After this grave data, we probably now understand the urgency of the water-saving quotes and the importance of water management.

Not to Scare But to Make an Aware – Save Water Save Life

The figures were not to raise an alarm but to make you aware and update you about the importance of water conservation. 

In this context, we are going to talk about water conservation and its importance, also we are going to narrate a short story on – save water, save life. 

A Short Story On – Save Water Save Life

There was a village boy named Sadhu. As a kid, he always used to rhyme “Water is a necessity! Water is important! Water is life!” He never wasted a single drop of water rather saved water and continued rhyming his rhyme on saving water. Years later, people in his village used water recklessly, but Sadhu did not. He tried to warn everybody and make them aware about saving water but none paid any heed to the little boy’s warning or rhyming.

Sadhu even showed how not to waste water. He demonstrated how to brush the teeth turning the tap off, using a bucket and a mug for bathing, and other such saving water tricks but still the people did not care much. 

Months went by, winters came. On a cold and frosty morning, the villagers woke up to find that there was no water. They called out to each other to check if anyone had water, but alas! no one had a single drop. They could not drink any water, wash their clothes, or take a bath the whole day. 

Finally, the villagers then approached Sadhu. They repented for their mistake of not saving any water. Sadhu reminded them of the importance of water. Sadhu was a kid so they allowed every villager to take a bucket of water that he had stored in the tank during the summer days. The villagers thanked Sadhu and promised themselves never to waste water. 

The next day, by god’s grace, the village welcomed winter rains. Their wells and tanks were again filled with sparkling water. Everyone in the village glittered with joy! 

After this learning, the villagers saved water and rhymed like Sadhu “Water is a necessity! Water is important! Water is life!”

Thus, do you see the importance of water? If we run out of water in a single day, it becomes hard for us to survive. 

How Can You Save Water?

In this section, we will share simple saving water tips which we all must follow. The tips are as follows:

You can save water by bathing in a bucket.

Do not use the shower even if you love using the shower, use it for shorter times.

Install a bucket or a tank under your roof where the water drips in the monsoon season. Freshwater from the rain will automatically get collected here. 

Turn off the tap while you are brushing your teeth.

Simple tricks and tips on saving the water will go a long run. As responsible earthlings, it is our prime duty to save water for the next generation. So, we all must come together and save water so that we do not face any day like the villagers faced in the story of Sadhu. 

FAQs on Short Story On Save Water Save Life

1. Why should we save water?

This is a harsh reality that we cannot live without water. Thus, we should save water for our own life. Also, for the future generation, we should responsibly save water.

2. What do you mean by water management?

Water Management is the process of planning, developing, and distributing the water resources efficiently in order to get the optimal use of this scarce resource. 

Essay on Water for Students and Children

500+ words essay on water.

Water is one of the most important substances for life on earth to function. It is equally important for humans as well as animals. Water does not merely help us survive, but it is significant for our day to day functioning. It has numerous uses when we come to think about it. Majority of our earth is covered with water itself, but, not all of it is safe for consumption. Therefore, it makes it essential for us to utilize this transparent substance chemical wisely. Moreover, if we look at the shortage of water happening in our country, it makes it all the more important to conserve it immediately.

Uses of Water

As we have already said that water has numerous uses, we will see where it is used. This part will most importantly help us realize the importance of water . It will make humans aware of what absence of water in the following areas can do to human life. As India’s main occupation is agriculture, water is exhaustively used here. Irrigation and cattle rearing requires a lot of water. Thus, a lot of farmers’ livelihood depends on it.

Further, industries use water for various purposes. It comes in handy when cooling, manufacturing and transporting several goods. For instance, thermal power plants consume quite a substantial amount of water for their running.

Furthermore, the domestic use of water cannot be left behind. In the day to day life of the common man, water plays a vital role. That is to say, from drinking water to washing utensils, we need water every step of the way.

After that, plants need water to survive and make food. It is one of the main elements which help them grow. Hence, water is extremely important for humans, animals, and plants to survive .

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Do not Waste Water

While water is quite essential and yet so scarce, however, people fail to realize this fact. They waste water with little or no care for the results of this activity. There are various ways in which one can avoid wasting water . To begin with, all households must get their leaking taps checked. They should fix them immediately as every drop is precious.

Similarly, we must choose buckets instead of showers for bathing. This is a very debatable topic and it needs to be settled. Showers waste a lot of water, so people must prefer buckets. This particular habit is quite commonly found in most of the households. People do not turn off their taps while brushing their teeth and washing utensils. Always remember to keep the tap off when doing so.

In addition, encourage rainwater harvesting system in all homes. This can help conserve water like never before.

In short, water is essential for the survival of mankind. But, it is, unfortunately, being waster rapidly. Every citizen and government must come together to tackle this issue. Governments must ensure all areas get water equally. On the other hand, citizens must keep in mind to use it wisely and not waste it unnecessarily.

FAQs on Water

Q.1 State the importance of water.

A.1 Water is of the utmost importance for human and animal life. It gives us water to drink. It also comes in great use for farmers and industries. Even common man requires water for various purposes like drinking, cleaning, bathing and more.

Q.2 List the ways to avoid wastage of water.

A.2 Everyone must avoid wasting water. We can do so by fixing our leaking taps, avoiding showers for bathing, and turning off taps when brushing. Furthermore, we can adopt rainwater harvesting system to conserve water.

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