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18, , Wastewater Story, , All of us use water in our homes and, make it dirty., Dirty! Are you surprised?, Rich in lather, mixed with oil, black–, brown water that goes down the drains, from sinks, showers, toilets, laundries, is dirty. It is called wastewater. This, used water should not be wasted. We, must clean it up by removing pollutants., Have you ever thought where the, wastewater goes and what happens to it?, , 18.1 W ATER, OUR LIFELINE, Clean water is a basic need of human, being. Let us make a mindmap of the, many uses of clean water., , Activity 18.1, (We have given one example of the, use of clean water. You can add many, more.), , Clean water, put to use, , Drinking, , Clean water that is fit, for use is unfortunately, not available to all. It has, been reported that more, than one billion of people, have no access to safe, drinking water. This accounts for a large, number of water-related diseases and, even deaths. People even children walk, for several kilometres to collect clean, water, as you read in Chapter 16. Is it, not a serious matter for human dignity?, You have studied in Chapter 16, about the increasing scarcity of freshwater due to population growth,, pollution, industrial development,, mismanagement and other factors., Realising the urgency of the situation, on the World Water Day, on 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., There has been perceptible progress, in the direction of the aim but still there, is a lot to achieve., Cleaning of water is a process of, removing pollutants before it enters a, water body or is reused. This process of, wastewater treatment is commonly, , 220, , SCIENCE, , 2020-21

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known as “Sewage Treatment”. It takes, place in several stages., , 18.2 WHAT IS SEWAGE?, Sewage is wastewater released by homes,, industries, hospitals, offices and other, users. It also includes rainwater that has, run down the street during a storm or, heavy rain. The water that washes off, roads and rooftops carries harmful, substances with it. Sewage is a liquid, waste. Most of it is water, which has, dissolved and suspended impurities., , Activity 18.2, Locate an open drain near your home,, school or on the roadside and inspect, water flowing through it., Record colour, odour and any other, observation. Discuss with your friends, and your teacher and fill up the, following Table 18.1., We know that sewage is a complex, mixture containing suspended solids,, organic and inorganic impurities,, nutrients, saprophytes and disease, causing bacteria and other microbes., These include the following., Organic impurities – Human faeces,, animal waste,, , oil, urea (urine),, pesticides,, herbicides, fruit, and vegetable, waste, etc., Inorganic impurities – Nitrates,, Phosphates,, metals., Nutrients, – Phosphorus, and Nitrogen., Bacteria, – Such as vibrio, cholera which, causes cholera, and salmonella, paratyphi which, causes typhoid., Other microbes, – Such as, protozones, which cause, dysentery., , 18.3 WATER FRESHENS UP — AN, E VENTFUL JOURNEY, In a home or a public building generally, one set of pipes brings clean water and, another set of pipes takes away, wastewater. Imagine that we could see, through the ground. We would see a, network of big and small pipes, called, , Table 18.1 Contaminant survey, S. No. Type of sewage Point of origin, , 1., , Sullage water, , Kitchen, , 2., , Foul waste, , Toilets, , 3., , Trade waste, , Industrial, and commercial, organisations, , WASTEWATER STORY, , Contaminants, , Any other, remark, , 221, , 2020-21

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sewers, forming the sewerage. It is like, a transport system that carries sewage, from the point of being produced to the, point of disposal, i.e. treatment plant., Manholes are located at every 50 m, to 60 m in the sewerage, at the junction, of two or more sewers and at points, where there is a change in direction., , Activity 18.3, Study the sewage route in your home/, school/building. Do the following:,  Make a line diagram of the sewage, route.,  Walk down the street or survey the, campus to find the number of, manholes.,  If possible, observe open drain and, record which living organisms are, found in and around it., In case you do not have a sewerage, system in your locality, find out how, sewage is being disposed off., , Treatment of polluted water, Perform the following activity. It will help, you understand the processes that take, place at the wastewater treatment plant., , Activity 18.4, Divide yourself into groups to perform, the activity. Record observations at each, stage:,  Fill a large glass jar 3/4 full of water., Add some dirty organic matter such, as grass pieces or orange peels, a, small amount of detergent, and a few, drops of an ink or any colour., , , , , , , , , , , , , , , , , , 222, , Cap the jar, shake it well and let the, mixture stand in the sun for two, days., After two days, shake the mixture, and pour a small sample into test, tube. Label this test tube “Before, treatment; Sample 1”. How does it, smell?, 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. You may have to stir it, several times., The next day when aeration is, complete, pour another sample into, a second test tube. Label it as “After, aeration; Sample 2”., Fold a piece of filter paper to form a, cone. Wet the paper with tap water, and then insert the cone in a funnel., Mount the funnel on a support, (as you have learnt in Class VI)., Place layers of sand, fine gravel and, finally medium gravel in the funnel, (Fig. 18.2). (An actual filtration plant, does not use filter paper, but the sand, filter is several metres deep)., Pour the remaining aerated liquid, through the filter into the beakers., Do not allow the liquid to spill over, the filter. If the filtered liquid is not, clear, filter it a few times till you get, clear water., Pour a sample of the filtered water, into a third test tube labelled, “Filtered; Sample 3”., , SCIENCE, , 2020-21

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1. Wastewater is passed through bar, screens. Large objects like rags,, sticks, cans, plastic packets, napkins, are removed (Fig. 18.3)., , Fig. 18.2 Filtration process, , , , Pour another sample of the filtered, water into a fourth test tube. Add a, small piece of a chlorine tablet. Mix, well until the water is clear. Label the, test tube “Chlorinated; Sample 4”.,  Observe carefully the samples in all, the test tubes. Do not taste! Just, smell them!, Now answer the following questions:, (a) What changes did you observe in the, appearance of the liquid after, aeration?, (b) Did aeration change the odour?, (c) What was removed by the sand filter?, (d) Did chlorine remove the colour?, (e) Did chlorine have an odour? Was it, worse than that of the wastewater?, , Fig. 18.3 Bar screen, , 2. Water then goes to a grit and sand, removal tank. The speed of the, incoming wastewater is decreased to, allow sand, grit and pebbles to settle, down (Fig. 18.4)., , 18.4 WASTEWATER TREATMENT PLANT, (WWTP), T reatment of wastewater involves, physical, chemical, and biological, processes, which remove physical,, chemical and biological matter that, contaminates the wastewater., , Fig. 18.4 Grit and sand removal tank, , 3. The water is then allowed to settle in, a large tank which is sloped towards, the middle. Solids like faeces settle, at the bottom and are removed with, , WASTEWATER STORY, , 223, , 2020-21

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Fig. 18.5 Water clarifer, , a scraper. This is the sludge. A, skimmer removes the floatable solids, like oil and grease. Water so cleared, is called clarified water (Fig. 18.5)., The sludge 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 or can be used to produce electricity., 4. Air is pumped into the clarified water, to help aerobic bacteria to grow., Bacteria consume human waste, food, waste, soaps and other unwanted, matter still remaining in clarified, water (Fig. 18.6)., , After several hours, the suspended, microbes settle at the bottom of the tank, as activated sludge. The water is then, removed from the top., 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., The treated water has a very low level, of organic material and suspended, matter. It is discharged into a sea, a river, or into the ground. Nature cleans it up, further. Sometimes it may be necessary, to disinfect water with chemicals like, chlorine and ozone before releasing it, into the distribution system., , Become an active citizen, Waste generation is a natural part of, human activity. But we can limit the, , The water in a river is cleaned, naturally by processes that are, similar to those adopted in a, wastewater treatment plant., , Did you know ?, It has been suggested that we should, plant eucalyptus trees all along, sewage ponds. These trees absorb all, surplus wastewater rapidly and, release pure water vapour into the, atmosphere., , Fig. 18.6 Aerator, 224, , SCIENCE, , 2020-21

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type of waste and quantity of waste, produced. Often we have been repelled, by 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., You can be an enlightened citizen, and approach the municipality or the, gram panchayat. Insist that the open, drains be covered. If the sewage of, any particular house makes the, neighbourhood dirty, you should, , , , Chemicals like paints, solvents,, insecticides, motor oil, medicines, may kill microbes that help purify, water. So do not throw them down, the drain., Used tealeaves, solid food remains,, soft toys, cotton, sanitary towels, etc., should also be thrown in the dustbin, (Fig. 18.7). These wastes choke the, drains. They do not allow free flow, of oxygen. This hampers the, degradation process., , , , Don’t add to the load of, WWTP. Paheli wonders how!, , request them to be more considerate, about others’ health., , 18.5 B ETTER HOUSEKEEPING, PRACTICES, One of the ways to minimise or eliminate, waste and pollutants at their source is, to see what you are releasing down the, drain.,  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., , Fig. 18.7 Do not throw everything in the sink, , WASTEWATER STORY, , 225, , 2020-21

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In the year 2016, the Government of India has initiated a new mission known as, “Swachh Bharat” under which a lot of drives such as proper sewage disposal, and providing toilets for everyone have been started., , Vermi-processing toilet, A design of a toilet in which humans excreta is treated by earthworms has been, tested in India. It has been found to be a novel, low water-use toilet for safe, processing of human waste. The operation of the toilet is very simple and hygienic., The human excreta is completely converted to vermi cakes — a resource much, needed for soil., , 18.6 SANITATION AND DISEASE, Poor sanitation and contaminated, drinking water is the cause of a large, number of diseases., Let us look at our own country. A, vast number of our people are still, without sewerage facilities. Where do, they relieve themselves?, A very large fraction of our people, defecates in the open, on dry riverbeds,, on railway tracks, near fields and many, a time directly in water. Untreated, human excreta is a health hazard. It, may cause water pollution and soil, pollution. Both the surface water and, groundwater get polluted. Groundwater, is a source of water for wells, tubewells,, springs and many rivers as you learnt, in Chapter 16. Thus, it becomes the most, common route for water borne diseases., They include cholera, typhoid, polio,, meningitis, hepatitis and dysentery., Bhoojo wants to know how, sewage is disposed of in an, aeroplane., , 18.7 ALTERNATIVE ARRANGEMENT, FOR SEWAGE DISPOSAL, To improve sanitation, low cost onsite, sewage disposal systems are being, encouraged. Examples are septic tanks,, chemical toilets, composting pits. Septic, tanks are suitable for places where there, is no sewerage system, for hospitals,, isolated buildings or a cluster of 4 to 5, houses., Some organisations offer hygienic, on-site human waste disposal, technology. These toilets do not require, scavenging. Excreta from the toilet seats, flow through covered drains into a, biogas plant. The biogas produced is, used as a source of energy., , 18.8 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., Large amount of waste is generated, , 226, , SCIENCE, , 2020-21

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here. 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., However, all of us can contribute in, maintaining sanitation at public places., We should not scatter litter anywhere., If there is no dustbin in sight, we should, carry the litter home and throw it in the, dustbin., , Conclusion, We all have a role to play in keeping our, environment clean and healthy. You, , must realise your 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 optimism. A lot can be done if people, work together. There is great power in, collective action., Mahatma Gandhi said:, “No one need to wait for anyone else, to adopt a humane and enlightened, course of action.”, , Keywords, Aeration, , Contaminant, , Sewerage, , Aerobic bacteria, , Sanitation, , Sludge, , Anaerobic bacteria, , Sewage, , Wastewater, , Biogas, , Sewer, , What you have learnt, , , Used water is wastewater. Wastewater could be reused., , , , Wastewater is generated in homes, industries, agricultural fields and in, other human activities. This is called sewage., , , , Sewage is a liquid waste which causes water and soil pollution., , , , Wastewater is treated in a sewage treatment plant., , , , Treatment plants reduce pollutants in wastewater to a level where nature, can take care of it., , , , Where underground sewerage systems and refuse disposal systems are, not available, the low cost on-site sanitation system can be adopted., , , , By-products of wastewater treatment are sludge and biogas., , , , Open drain system is a breeding place for flies, mosquitoes and organisms, which cause diseases., , , , We should not defecate in the open. It is possible to have safe disposal of, excreta by low cost methods., , WASTEWATER STORY, , 227, , 2020-21

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Exercises, 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 ____________., , 2. What is sewage? Explain why it is harmful to discharge untreated, sewage into rivers or seas., 3. Why should oils and fats be not released in the drain? Explain., 4. Describe the steps involved in getting clarified water from wastewater., 5. What is sludge? Explain how it is treated., 6. Untreated human excreta is a health hazard. Explain., 7. Name two chemicals used to disinfect water., 8. Explain the function of bar screens in a wastewater treatment plant., 9. Explain the relationship between sanitation and disease., 10. Outline your role as an active citizen in relation to sanitation., 11. Here is a crossword puzzle: Good luck!, , 228, , SCIENCE, , 2020-21

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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, , 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, , Extended Learning — Activities and Projects, 1. Construct a crossword puzzle of your own using the keywords., 2. Then and now: Talk to your grand parents and other elderly people in, the neighbourhood. Find out the sewage disposal systems available to, them. You can also write letters to people living in far off places to get, more information. Prepare a brief report on the information you, collected., 3. Visit a sewage treatment plant., It could be as exciting and enriching as a visit to a zoo, a museum, or a, park. To guide your observation here are a few suggestions., Record in your notepad:, Place ___________, , Date ___________, , Time ___________, , Name of the official at the plant __________ Guide/Teacher ___________, , WASTEWATER STORY, , 229, , 2020-21

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(a), , The location of the sewage plant., , (b), , Treatment capacity., , (c), , The purpose of screening as the initial process., , (d), , How is air bubbled through the aeration tank?, , (e), , How safe is the water at the end of the treatment? How is it tested?, , (f ), , Where is the water discharged after treatment?, , (g), , What happens to the plant during heavy rains?, , (h), , Is biogas consumed within the plant or sold to other consumers?, , (i), , What happens to the treated sludge?, , (j), , Is there any special effort to protect nearby houses from the plant?, , (k), , Other observations., , For more information, consult:, Millennium Development Goals:, http://www.un.org/millenniumgoals/, “Water for Life” International Decade for Action:, http://www.un.org/waterforlifedecade/, http://www.cep.unep.org/pubs/Techreports/tr43en/Household%, 20systems.htm, , “By providing clean water and sanitation to the poorest people on the, planet, we can reduce poverty and suffering and ensure education for all, children.” — UNICEF, An early engineering feat: Indus valley civilisation, One of the ancient civilisations, Harappa and Mohenjodaro had perhaps, the world’s first urban sanitation system. Within the city individual, houses, or groups of houses, obtained water from wells. There was a, separate room for bathing, and wastewater was directed to the covered, drains which lined the major streets. The oldest toilet made of bricks is, about 4500 years old., , 230, , SCIENCE, , 2020-21