Question

The domestic sewage in large cities
A. Has a high BOD as it contains both aerobic and anaerobic bacteria.
B. Is processed by aerobic and then anaerobic bacteria in the secondary treatment in sewage treatment plants (STPs).
C. When treated in STPs does not really require the aeration step as the sewage contains adequate oxygen.
D. Has very high amounts of suspended solids and dissolved salts.

Answer 1

Hint:- Sewage is wastewater having food buildup, creature and human excreta and waste material from mechanical foundations.In simple terms, it is untreated wastes which goes through a sewer system. Domestic sewage generated by treatment thereof in sanitary sewage collection, treatment and disposal systems which are made to release effluents to the water bodies.

Complete step-by-step solution:- Sewage treatment is the way toward eliminating foreign substances from city wastewater, containing chiefly family unit sewage in addition to some mechanical wastewater. Physical, compound, and organic cycles are utilized to eliminate pollutants and produce treated wastewater that is sheltered enough for discharge into the climate. A side-effect of sewage treatment is a semi-strong waste or slurry, called sewage ooze. The slime needs to go through additional treatment before being reasonable for removal or application to land.
Sewage treatment may likewise be alluded to as wastewater treatment. In any case, the last is a more extensive term which can likewise allude to mechanical wastewater. For most urban communities, the sewer framework will likewise convey an extent of mechanical profusion to the sewage treatment plant which has typically gotten pre-treatment at the industrial facilities themselves to lessen the contamination load. In the event that the sewer framework is a consolidated sewer, at that point it will likewise convey metropolitan spillover to the sewage treatment plant. Sewage water can go towards treatment plants through channeling and in a stream supported by gravity and siphons. The initial segment of filtration of sewage ordinarily incorporates a bar screen to channel solids and enormous items which are then gathered in dumpsters and discarded in landfills. Fat and oil are likewise eliminated before the essential treatment of sewage.
Correct Option: - (B) Is processed by aerobic and then anaerobic bacteria in the secondary treatment in sewage treatment plants (STPs).

Note:- The homegrown sewage in huge urban areas is prepared by vigorous and afterward anaerobic microbes in the optional treatment in sewage treatment plants (STP).
Treatment of water: -
1. Primary treatment - The treatment uses settling tanks of upward, even tanks. The water stream is prompted to permit 15-45 min maintenance time during which 70% of suspended solids either settle to base or stream as filth on the top.
2. Secondary treatment - Digestion of natural issues disintegrated in wastewater by high-impact/anaerobic cycles.
3. Tertiary structure - The point of this progression is to eliminate suspended issues and to decrease BOD even more. The cycles utilized are either physical or compound.
4. Sludge treatment - Sludge is the settled strong segment of water recouped during the treatment measures. It is dealt with mostly anaerobically to make it safe before removal.