Civil Engineering - Waste Water Engineering - Discussion

Sludge digestion tanks work only in anaerobic condition. So C should be the right answer.

Option (a) Imhoff tank is the correct option.

Explanation.

A trickling filter is a type of wastewater treatment system. It consists of a fixed bed of rocks, coke, gravel, slag, polyurethane foam, sphagnum peat moss, ceramic, or plastic media over which sewage or other wastewater flows downward and causes a layer of microbial slime (biofilm) to grow, covering the bed of media. Aerobic conditions are maintained by splashing, diffusion, and either by forced-air flowing through the bed or natural convection of air if the filter medium is porous.

In Imhoff tank, there are two parts.

1. Sedimentation takes place, which is exposed to the atmosphere i.e. aerobic.

2. Digestion tank which is not exposed to air i.e anareobic.

The correct option is A".

Here, it should be "aerobic" not anaerobic.

ASP is a suspended growth aerobic process.

A trickling filter is an attached growth aerobic process.

Imhoff tank has dual character (ie) aerobic in nature in the upper portion and anaerobic in the lower portion.

So, none of these is the correct option.

Method => Contact Mechanism => Decomposition.
.
1. Trickling filter => Attached growth=> Aerobic.
2. Rotating biological contactor => Attached growth => Aerobic.
3. Activated sludge process => Suspended growth => Aerobic.
4. Oxidation pond => Suspended growth => Aerobic.
5. Septic tank => Suspended growth => Anaerobic.
6. Imhoff tank => Suspended growth => Anaerobic