Question

Sludge is
A. created from combination of gases released from industries and water
B. a semi-solid slurry and can be produced as sewage sludge from wastewater treatment processes
C. a type of household waste
D. a type of industrial waste

Answer 1

Sludge means the waste obtained from treatment of waste water processes from industries. Sludge has many applications in several wastewater treatment processes in different industries for obtaining drinking water.

Complete step by step answer:
It is a semi solid slurry of various substances obtained from industries after water treatment, wastewater treatment and various other sanitation processes. Sludge is composed of both organic and inorganic material.
It is a type of suspension which is rich in plant nutrients and so are useful fertilizers. The semi-solid substances which settle down during wastewater treatment are called sludge. The sludge is removed using a scraper and then it is transferred to a tank for decomposition by anaerobic bacteria and finally generates biogas.
By nature there are two types of sludges and classified by the contents of biogas potential. One is known as primary and the other known as secondary. Primary sludge results from the capture of suspended solids and organics in the primary treatment process through gravitational sedimentation. On the other hand, the secondary process involves microorganisms to consume the organic matter in the wastewater for producing the sludge.
Hence primary sludge contains higher biogas production potential as energy content is not consumed during the capture. Secondary sludge has lower biogas potential as the microorganisms have consumed most of their energy content with release of inert biomass.

Thus, the correct option is option (B).

Note:
Sludge is one of the important substitutes used for producing various pure water and several other industrial prepared substances. Sewage should not be confused with sludge as sewage is a liquid containing waste while sludge is solid waste collected after treatment in wastewater treatment.