1. What gas is associated with the formation of foam?
a. carbon dioxide
b. methane
c. nitrogen
d. hydrogen sulfide

2. The most commonly found scaling problem in an anaerobic digester is _.
a. calcium carbonate
b. magnesium ammonium phosphate
c. sodium chloride
d. calcium ammonium phosphate

3. Which of the following can cause foaming in an anaerobic digester?
a. nocardia
b. fluctuating temperatures
c. inadequate mixing
d. all the above

4. When an employee becomes angry, his boss should _.
a. react with anger
b. listen with apprehension
c. laugh at him
d. actively listen to determine the problem

5. An operator runs a Winkler by the azide modification of the Winkler method. He runs out of standard sodium thiosulfate. Which reagent can be substituted?
a. calcium hypochlorite
b. phenylarsenine oxide
c. sodium bicarbonate
d. ferrous ammonium sulfate

Answers:

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