What is sewage?Explain in long answer.
Answers
Answer:
Sewage is waste matter such as faeces or dirty water from homes and factories, which flows away through sewers. ... the MPs' call for more treatment of raw sewage.
(a) Primary treatment: It involves the physical removal of particles from sewage through filtration and sedimentation. Floating debris is removed by filtration and grit is removed by sedimentation. Thus, all solids which settle form the primary sludge and the supernatant forms the effluent.
Secondary treatment: The effluent from primary treatment is passed to aeration tanks where the air is pumped into it. This allows the growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments) and microbes consume the major part of the organic matter in the effluent. This reduces the BOD (biological oxygen demand) of the effluent. The effluent is then passed into the settling tank where bacterial flocs are allowed to sediment. This sediment is called activated sludge. The small portion of this activated sludge is again passed to the aeration tank to serve as inocula. The remaining major part of this sludge is pumped into large anaerobic sludge digesters. Here, anaerobic bacteria digest bacteria and fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, H2S, and CO2. This treatment is essential as the sewage or municipal waste discharged into rivers, streams and other water bodies contains human excreta, organic wastes, and several pathogenic microbes.