16. Oxidation ponds are shallow ponds, generally designed at the depth of

A. 2 to 40 feet
B. 4 to 6 feet
C. 1 to 3 feet
D. 5 to 8 feet

17. Which of the following is generally not referred to the sewerage system?

A. Sanitary sewers
B. Storm sewers
C. Combined sewers
D. Solid sewers

18. The magnitude of BOD of wastewater is related to

A. bacterial count
B. amount of organic material
C. amount of inorganic material
D. all of the above

19. A dense bacterial population caught in a tangled web of fibers sticking to a surface describes

A. coagulation
B. a biodisc
C. a biofilm
D. the membrane filter technique

20. Biogas production is

A. a temperature-dependent process
B. a temperature independent process
C. an oxygen dependent process
D. none of the above