Question

What is dewatered sludge?

(a) Separation of liquid and solid phase

(b) Product of wastewater treatment

(c) Type of wastewater treatment

(d) Suspended solids

This question was posed to me in exam.

This key question is from By-Products in section Effluent Treatment of Bioprocess Engineering

Answer 1

The correct answer is:

(b) Product of wastewater treatment

Dewatered sludge refers to the solid by-product of wastewater treatment, which has had a significant portion of its water content removed through processes such as centrifugation, filtration, or pressing. The resulting material is more concentrated and easier to handle, store, or dispose of compared to untreated sludge, which contains a higher percentage of water. Dewatered sludge is typically further processed or disposed of, and may also be used in some applications like landfilling or as fertilizer (depending on its composition).

Here's a breakdown of the options:

• (a) Separation of liquid and solid phase: While this describes the general process in wastewater treatment, it’s more about the method rather than the specific product.

• (b) Product of wastewater treatment: Correct. Dewatered sludge is a by-product after wastewater treatment where the liquid phase is separated from the solids.

• (c) Type of wastewater treatment: Dewatering is a process, but not a type of wastewater treatment itself. It's part of post-treatment processes.

• (d) Suspended solids: This refers to particles in wastewater before treatment, not the dewatered product.

So, the right choice is (b) Product of wastewater treatment.