Class C Wastewater Sample Questions

Question 1

1.) The first step in anaerobic digestion is called

Answer 1

Acid formation

Question 2

2.) pH is the measure of

Answer 2

Intensity of basic or acidic condition of a liquid

Question 3

3.) The second stage of anaerobic digestion is called

Answer 3

Methane formation

Question 4

4.) The two primary gases formed in the anaerobic digestion process are

Answer 4

Methane and carbon dioxide

Question 5

5.) One liter of liquid chlorine can evaporate and produce how many liters of chlorine gas?

Answer 5

460

Question 6

6.) Samples taken for pH measurement should be

Answer 6

Tested as soon as possible

Question 7

7.) What is the desired DO level in the first stage of an RBC?

Answer 7

1 to 3 mg/L

Question 8

8.) Packing glands on centrifugal pumps should be

Answer 8

Tightened enough to allow a leak of one drip per second

Question 9

9.) PROBLEM: Plant effluent coliform count fails to meet required standards for disinfection. Chlorine residual is adequate. Disinfectant supply not a problem.

Probable cause:

Answer 9

Contact time too short

Question 10

10.) In a well operated activated sludge plant, when the RAS rate is decreased but the WAS rate remains constant, the expected conditions would be

Answer 10

RAS CONC: Increase
WAS CONC: Increase
MLSS CONC: Decrease 
F/M Ratio: Increase 
MCRT: Decrease

Question 11

11.) In an activated sludge plant, if the DO in the aeration tank suddenly decreases and the aerators are not the problem, what is the most probable cause?

Answer 11

Increased organic load

Question 12

12.) The most important adjustments to the activated sludge process are made by adjusting

Answer 12

RAS, WAS and aeration

Question 13

13.) PROBLEM: Classic sludge bulking occurring in the final clarifier of a conventional activated sludge plant. Indicators include solids pouring over the weirs, excessive floc observed at the surface, and a homogenous sludge blanket appearing throughout the clarifier. Sludge in settling test settles slowly leaving a cloudy effluent.
Probable Cause:

Answer 13

Young sludge

Question 14

14.) PROBLEM: Classic sludge bulking occurring in the final clarifier of a conventional activated sludge plant. Indicators include solids pouring over the weirs, excessive floc observed at the surface, and a homogenous sludge blanket appearing throughout the clarifier. Sludge in settling test settles slowly leaving a cloudy effluent.
Neccesary Check:

Answer 14

Calculate sludge age

Question 15

15.) PROBLEM: Classic sludge bulking occurring in the final clarifier of a conventional activated sludge plant. Indicators include solids pouring over the weirs, excessive floc observed at the surface, and a homogenous sludge blanket appearing throughout the clarifier. Sludge in settling test settles slowly leaving a cloudy effluent.
Best solution:

Answer 15

Reduce sludge wasting

Question 16

16:) PROBLEM: Excessive white foam in the aeration tank

Probable Cause:

Answer 16

MLSS too low

Question 17

17.) PROBLEM: Excessive white foam in the aeration tank

Neccessary Check:

Answer 17

MLSS

Question 18

18.) PROBLEM: Excessive white foam in the aeration tank

Solution:

Answer 18

Increase MLSS

Question 19

19.) PROBLEM: Good settling in the 30 minute settleability test. Excessive floc billowing in the clarifier and washing out.
Probable Cause:

Answer 19

Hydraulic overload

Question 20

20.) PROBLEM: Good settling in the 30 minute settleability test. Excessive floc billowing in the clarifier and washing out.
Neccasary Check:

Answer 20

Clarifier overflow rate

Question 21

21.) PROBLEM: Good settling in the 30 minute settleability test. Excessive floc billowing in the clarifier and washing out.
Best Solution:

Answer 21

Reduce clarifier loading rates

Question 22

22.) In most activated sludge treatment plants, the major cause of repeated sludge bulking is

Answer 22

High F/M loading rates and low MCRT

Question 23

23.) What happens in the stabilization (reaeration) tank in the contact-stabilization process?

Answer 23

Digestion of the waste material collected by microorganisms

Question 24

24.) A problem associated with trickling filters is

Answer 24

Ponding

Question 25

32. In a properly operating facultative pond, algae live on carbon dioxide and nutrients during the
    day, and at night produce carbon dioxide.
    This has what effect on the pH?

Answer 25

pH increases during the day, and decreases at night

Question 26

33. A pond operating depth of _____
    is recommended to prevent excessive weed and cattail
    growth.

Answer 26

At least three feet

Question 27

34. An aerobic pond is a pond that

Answer 27

Has DO distributed throughout the entire contents all the time

Question 28

35. Excessive odors are noticed around the primary clarifier. Bubbles are seen throughout the clarifier, and sludge is rising to the surface. What is the cause?

Answer 28

Sludge decomposing in tank

Solution- Check Sludge collection mechanism

Question 29

37. A ________ is designed to deliver an accurate volume of sample or reagent when testing
    wastewater in a laboratory?

Answer 29

Pipet

Question 30

38. The largest sources of error found in laboratory results are usually caused by:

Answer 30

Poor preservation techniques