| Question - 1 of 10 | a | b | c | d |
| What should the percentage of settled sludge be when running the 30 - minute settleability test ? | Less than 50 % | Between 10 % - 70 % | Less than 40 % | Between 70 % - 80 % |
| Question - 2 of 10 | a | b | c | d |
| A sample of the plant effluent from a well operating treatment plant would appear ; | Cloudy with a few light suspended solids | Clear with less than 10 mg / L solids at the bottom of the Imhoff cone | Clear with less than 5 mg / L solids at the bottom of the Imhoff cone | Clear with a few light suspended solids and a trace of solids at the bottom of the Imhoff cone |
| Question - 3 of 10 | a | b | c | d |
| The operator can determine when to plan on removing excess solids from the plant by observing the rate of solids build - up in the aeration tank. Excess solids should be removed when the percent of sludge in the 30 - minute settleability test is approximately ; | 80 % - 90 % | 50 % - 70 % | 20 % - 40 % | 10 % - 20 % |
| Question - 4 of 10 | a | b | c | d |
| When the supernatant in the aeration tank sample is clear but the effluent sample is cloudy, the trouble usually is ; | In the settling tank | In the aeration tank | Due to a significiant increase in sewage flow | Due to a lack of DO in the aeration tank |
| Question - 5 of 10 | a | b | c | d |
| If the settled sludge is held in the settling tank too long, it will ; | Pack, solid and be difficult to remove | Become septic | Become alkaline | Aerobically digested |
| Question - 6 of 10 | a | b | c | d |
| When the supernatant in the aeration tank sample is cloudy and the plant effluent sample is cloudy, the problem usually is ; | In the settling tank | Due to a lack of sludge in the aeration tank | Due to a lack of DO in the aeration tank | Due to the aeration tank being overaerated |
| Question - 7 of 10 | a | b | c | d |
| When the color of the sludge in the aeration tank changes from dark to light brown and, (1) the aeration tank sample supernatant is clear, and (2) the effluent sample is clear but contains a relatively large amounts of sludge, the problem is probably due to ; | An excessive increase in wastewater flow | An excessive decrease in wastewater flow | A lack of DO in the aeration tank | The aeration tank being overaerated |
| Question - 8 of 10 | a | b | c | d |
| Solids are being washed from the plant, this condition may be partially corrected by ; | Increasing the speed of the air blower to supply more air to the aeration tank | Discontinue operating the surface skimmer | Decrease the air supply to the aeration tank | Decrease the rate of returning sludge |
| Question - 9 of 10 | a | b | c | d |
| And another action would be ; | Increasing the speed of the air blower to supply more air to the aeration tank | Decreasing the speed of the air blower to supply low air to the aeration tank | Discontinue operation of the foam spray system | Decrease the rate of returning sludge |
| Question - 10 of 10 | a | b | c | d |
| As an operator, how can you recognize that in the settling tank denitrification occurs ? | DO test on the sample taken from the aeration tank | Gas bubling at the surface of the settling tank | pH test on the sample taken from the aeration tank | pH test on the sample taken from the settling tank |
