16. Trickling filter comes under

A. primary treatment
B. secondary treatment
C. tertiary treatment
D. none of these

17. Which of the following species in water reveal the presence of fecal pollution of human or animal origin?

A. E.coli
B. Fecal Streptococci
C. Clostridium perfringens
D. All of these

18. Activated sludge undergoes

A. Primary treatment
B. Secondary treatment
C. Tertiary treatment
D. any of these

19. The rate of flux of oxygen in the air is __________ to/than the rate of flux of oxygen in the water.

A. greater
B. lesser
C. approximately equal
D. half

20. __________ is an environment like __________ where microorganisms are functioning in an extremely thin film of water and where oxygen-containing air is close to them.

A. low oxygen diffusion environment; soils
B. high oxygen diffusion environment; soils
C. low oxygen diffusion environment; lakes
D. high oxygen diffusion environment; lakes