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com www.GOALias.blogspot.com www.GOALias ... - fun learning

com www.GOALias.blogspot.com www.GOALias ... - fun learning

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<strong>www</strong>.<strong>GOALias</strong>.<strong>blogspot</strong>.<strong>com</strong>of two or more sewers and at pointswhere there is a change in direction.Activity 18.3Study the sewage route in your home/school/building. Do the following:• Make a line diagram of the sewageroute.• Walk down the street or survey thecampus to find the number ofmanholes.• Follow an open drain and find outwhere it ends and which livingorganisms are found in andaround it.In case you do not have a seweragesystem in your locality, find out howsewage is being disposed off.Treatment of polluted waterPerform the following activity. It will helpyou understand the processes that takeplace at the wastewater treatment plant.Activity 18.4Divide yourself into groups to performthe activity. Record observations at eachstage:• Fill a large glass jar 3/4 full of water.Add some dirty organic matter suchas grass pieces or orange peels, asmall amount of detergent, and a fewdrops of an ink or any colour.• Cap the jar, shake it well and let themixture stand in the sun for twodays.• After two days, shake the mixtureand pour a small sample into testtube. Label this test tube “Beforetreatment; Sample 1”. How does itsmell?• Use an aerator from an aquarium tobubble air through the sample in theglass jar. Allow several hours foraeration; leave the aerator attachedovernight. If you do not have anaerator, use a mechanical stirrer ora mixer. You may have to stir itseveral times.• The next day when aeration is<strong>com</strong>plete, pour another sample intoa second test tube. Label it as “Afteraeration; Sample 2”.• Fold a piece of filter paper to form acone. Wet the paper with tap waterand then insert the cone in a <strong>fun</strong>nel.Mount the <strong>fun</strong>nel on a support(as you have learnt in Class VI).• Place layers of sand, fine gravel andfinally medium gravel in the <strong>fun</strong>nel(Fig. 18.2). (An actual filtration plantdoes not use filter paper, but the sandfilter is several metres deep).• Pour the remaining aerated liquidthrough the filter into the beakers.Do not allow the liquid to spill overthe filter. If the filtered liquid is notclear, filter it a few times till you getclear water.• Pour a sample of the filtered waterinto a third test tube labelled“Filtered; Sample 3”.• Pour another sample of the filteredwater into a fourth test tube. Add asmall piece of a chlorine tablet. Mixwell until the water is clear. Label thetest tube “Chlorinated; Sample 4”.222SCIENCE

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