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Question 1: Qnol Queso (Pg no: 238), , Sewage largely consists of wastewater. Where is this wastewater, generated?, , Answer :, , Wastewater can be generated in houses during bathing, washing clothes, and flushing toilets. Moreover, wastewater is also produced by hospitals,, industries, offices and hotels., , Question 2:, Why are open drains considered to be unhygienic?, Answer :, , Open drains are frequently blocked due to plastic bags and sewage. This, results in the overflow, which produces foul smell and also provides a, breeding ground for germs and mosquitoes. These organisms cause wide, range of diseases. This is the reason for open drains to be considered, unhygienic., , Question 3 :, , No contamination of drinking water can occur if closed pipes are used, for drainage of sewage. Is this always true? Explain., , Answer :, , The contamination of drinking water can occur even if closed pipes are, used for the drainage of sewage. This is because in many cases, the joints, between the sewage lines may be leaky and this can lead to the leakage, of sewage. This sewage can mix with the drinking water if the sewage, line and water pipeline are proximate to each other.
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Question 1: Long Bnswers Ys no = 242), , List the ways in which wastewater present in sewage is generated and, the kind of contaminants present in each., , Answer :, , Sewage wastewater includes:, , (i) Waste water generated in houses during bathing, washing and, cleaning kitchen utensils, which contains detergent and dirt as well as, faeces and urine., , (ii) Wastewater generated in industries and hospitals, which contains, poisonous chemicals., , (iii) Rainwater that has run down, which contains harmful substances., , Question 2:, What problems can arise due to improper drainage?, Answer :, , Improper drainage can create unhygienic and unsanitary conditions in, our neighbourhood. Open, dirty and stagnant water serves as breeding, place for flies and mosquitoes. Sometimes, the river water and, groundwater, which are sources of drinking water, get contaminated, with human excreta and can spread water-borne diseases like cholera,, typhoid etc., , Question 3:, , What dangers result from improper storm water drainage system ina, city?, , Answer :, , Improper storm drainage system in a city can lead to contamination of, drinking water, bursting of pipelines and back flow of sewers. It is, , dangerous for public health and property. Contamination of drinking, water can spread water-borne diseases like cholera, typhoid etc.
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Question 4:, Outline the main steps used in sewage treatment., Answer :, , Following are the steps involved in the sewage treatment :, , (i) The sewage entering into the sewage treatment plant is first passed, through vertical bars to remove large rubbish objects like rags, sticks,, cans, plastic bags etc., , Gi) Then the water is made to flow through settling tank. This is done to, remove the grit and sand present in it., , (iii) The wastewater is then passed through the first sedimentation tank, and allowed to stay there for a while., , (iv) The sludge is then taken out from the bottom and put into a large,, closed tank called digester tank., , (v) The floating materials are removed by a skimmer., , (vi) The clarified water is then passed through the aeration tank, where, aerobic bacteria consume or digest organic wastes such as human waste,, food waste, soap and other unwanted materials., , (vil) From the aeration tank, treated water goes to the second, sedimentation tank and allowed again to stay there for a while., , (viii) The treated water left in the second sedimentation tank has low, level of organic materials and suspended impurities. The treated water is, then released in the river., , Question 5:, In what ways is the sludge obtained from a WWTP used?, , Answer :, , The sludge obtained from a wastewater treatment plant (WWTP) is used, as manure and biogas. The dried manure returns the nutrients to the, soil, whereas biogas is used as a fuel., , Question 6 :, , How can each one of us help in making the sewage treatment in our city, more efficient?, , Answer :, , Sewage treatment can be made more efficient by taking following, precautions:, , (i) Do not throw wastes such as solid food remains like tea leaves,, sanitary towels, polythene bags, soft toys etc. down the drain., , (ii) Do not throw waste cooking oil and fat in kitchen sink as they can, harden and block the drainage pipe., , (iii) Do not throw chemicals like paint, solvent, insecticides, medicines, etc. in the drainage pipe.
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Question 7 :, , Mention three ways that can be used for sewage disposal if a proper, sewage treatment plant is not available., , Answer :, , Followings are the three ways that can be used for sewage disposal if a, proper sewage treatment plant is not available:, , (i) Making septic tanks or septic tank toilets: It is suitable for places that, have no sewerage system., , (ii) Making vermi-processing toilet: Here, the sewage is treated by, earthworms in a pit. The earthworms gradually eat all the organic, matters and decompose it., , (iii) Use of human excreta in biogas plants: Here, the human excreta, from the toilet seats in the homes travels directly to biogas plants, through covered drains., , Question 1: Hats qruerstrows, (P3n0' 242), , Which pipes should be bigger-those used for sewage disposal or those, used for storm water disposal? Why?, , Answer :, , The pipe used for storm water disposal should be bigger, ie., it should, have large diameter. This is because, when it rains very heavily, large, amount of water comes down in a short time. If the diameter of the pipe, is small, water will overflow on the streets and may cause major health, risks by contaminating drinking water supplies., , Question 2:, , We realise that plastics, being non-biodegradable, are an environment, hazard. However, while discussing the choking of sewage drains by, plastics, why do we only talk about plastic carry bags and not of other, plastic products?, , Answer :, , In recent times, usage of plastic carry bags has increased at an alarming, rate than other plastic products. Plastic carry bags are often thrown here, and there. This clogs up gutters and drains and causes water and sewage, to overflow in our homes and public areas.
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Question 1: Volury, ( Pg no: 243), , You go to the market and buy a toy. After coming home you remove the, plastic packaging material in which the toy is wrapped, and throw it, carelessly in a drain outside your home. What can be the result of your, carelessness? What should you have done?, , Answer :, , The plastic which has been thrown in the drain can block the drain or it, can travel to a water body and harm the aquatic life., , The plastic could have been disposed in a safer manner or it may have, been reused for some other purpose., , Question 1: Qial Guusleons (hy no: 240), , What is the aim of sewage treatment?, Answer :, , The basic aim of sewage is to remove solid impurities from the sewage, and to make the liquid component of the sewage safer for fish and, humans when this sewage is discharged into water bodies., , Question 2:, , Why should you not throw the following into the kitchen sink or flush, them down the toilet?, , a. cooking oil, , b. sanitary napkins, , c. paints, , Answer :, , a. Cooking oil have the ability to block pipes due to their tendency to, harden., , b. Sanitary napkins clog the drains and obstruct with the free flow of, oxygen, which is required for the proper decomposition of waste., , c. Paints are toxic to microorganism and kill microbes that are essential, for cleaning the water.
