Preliminary Treatment

Question 1

The purpose of preliminary treatment in a wastewater treatment plant is to:

a) Provide a good place to start a treatment plant tour
b) Reduce BOD by removing as much inorganic material as possible
c) Remove non-biodegradable material which might cause damage to downstream equipment
d) Freshen wastewater to reduce the production of sludge in secondary treatment processes

Answer 1

c) Remove non-biodegradable material which might cause damage to downstream equipment

Question 2

What pieces of equipment are typically used to remove rocks, debris, and rags from the influent to a treatment plant?

a) Primary clarifiers, gravity belt thickener, micro-screens
b) Grit cyclones, centrifugal pumps, sludge disintegrator
c) Bar screen, trash rack, comminutor
d) Aerated grit chamber, rapid sand filter, grit classifier

Answer 2

c) Bar screen, trash rack, comminutor

Question 3

The target velocity for removal of grit in a non-aerated grit chamber or channel is:

a) 0.03 m/second
b) 0.4 - 0.6 m/second
c) 0.2 - 0.4 m/second
d) 1.0 m/second

Answer 3

c) 0.2 - 0.4 m/second

Question 4

Septage does not impose a high organic load on a wastewater treatment plant because all of the organic material has been decomposed in the septic tank prior to its arrival at the treatment plant.

a) True
b) False

Answer 4

b) False

Question 5

Bar screens, trash racks, comminutors, and macerators are all designed to reduce the particle size of materials entering the treatment plant.

a) True
b) False

Answer 5

b) False