Question

Among the following, which do not come under the category of sewage treatment?
A.The organic material present in the waste is allowed to undergo microbial oxidation
B.Large size materials are filtered through screen
C.The wastewater is suitably treated for the removal of phosphate by coagulation method
D.Degrading the number of toxic organic waste

Answer 1

Hint: Water, where it contains enough impurities to make it unfit for a specific purpose, such as drinking, bathing, or fishing, is considered to be contaminated. Sewage treatment is treatment of wastewater. Waste water is mainly treated in three stages; primary, secondary and tertiary.

Complete step by step answer:
Let us first understand the procedures in sewage treatment;
As we saw, there are three stages in sewage treatment each of them goes as follows;
The first step of sewage treatment is primary treatment: waste water is deposited in a storage tank and solids settle to the bottom where they are extracted and the top is scraped off with lighter compounds such as fats and oils.
Secondary treatment is where aerobic bacteria incorporated in the wastewater treatment system break down waste.
Tertiary treatment is meant to clean out nutrients and waste particles that could harm fragile habitats. Here, in order to remove extra nutrients, waste water is passed through additional filtration lagoons or tanks.
So, from the above explanations it is clear that the only step excluded in this sewage treatment is degradation of the toxic organic wastes.
So, for this question option D is the correct answer.


Note:
During primary treatment, sewage sludge scraped from the bottom of the settling tank is treated separately from waste water. It is possible to dispose of sludge in many ways. Then, bacteria may be used to digest it; often, bacterial digestion may create methane biogas, which is used to generate electricity. Sludge may also be incinerated, or diluted, heated and reused as fertiliser to clean it.