1. In dissolved air floatation thickeners floated solids are kept out of the effluent by use of _.
a. effluent baffles
b. hardware cloth screens
c. macroscreens
d. scum scrapers
e. water sprays

2. Cyrogenic oxygen plants are usually shut down _ for maintenance.
a. once every six months
b. once every year
c. once every two years
d. once every five years
e. once every ten years

3. High-rate anaerobic digestion refers to the fact that the organic waste material is applied to an anaerobic digester at a high _ loading rate.
a. gravimetric
b. hydraulic
c. organic
d. volumetric

4. The best water quality indicator to monitor enhanced nitrogen oxidation process is _.
a. alkalinity
b. MLSS
c. pH
d. temperature

5. What external chemical is added to achieve denitrification?
a. chlorine
b. liquid oxygen
c. metal salts
d. methanol

Answers:

1. a
2. b
3. d
4. a
5. d