B. Answer the following questions. a) give the reason why the sewage should be treated before being discharged in a water body? b) what is sewage? explain why is it harmful to discharge untreated sewage into river or seas? c) what do you mean by sewerage system? d) wastewater is Passed through bar screens during the process of wastewater. Why? e) what is sludge? Explain how it is treated?
Answers
Heya!
➦ untreated sewage contains a wide variety of dissolved and suspended impurities. hence, it is necessary to treat sewage before disposing it in a water body to remove its impurity and to prevent its devastating effect on humans, animals, fishes and Birds.
➦ sewage is a liquid waste which has water as its largest component along with various types of impurities like wastewaters from houses, offices, factories, hospitals etc., is called sewage. it has a complex mixture containing suspended solids, organic and inorganic impurities, nutrients and disease causing bacteria and other microbes.
discharging untreated sewage into river or seas will pollute the water resources. contaminated water is dangerous for aquatic plants and animals. it also spread many diseases like cholera, typhoid, polio, meningitis, malaria, dengue etc.
➦ Sewage is a network of big and small pipes called sewers placed under the ground. it can be considered as a transport system that carries wastewater from the point where it is produced to the point of disposal.
➦ sludge is a human waste ( like faeces ) in water left during sewage treatment. since it is organic waste, it is used to produce biogas and manure.
Sludge is collected by scrapper. it is transferred to a separate tank where it is decomposed by anaerobic bacteria. the biogas produced in the process can be used as a fuel. after the 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.