| Question - 1 of 14 | a | b | c | d |
| When the plant is operating properly, what is color of liquid in the aeration tank ? | Dark chocolate brown | Light brown | Grey | Black |
| Question - 2 of 14 | a | b | c | d |
| A color change from dark brown to light brown often indicates that ; | the aeration tank dissolved oxygen level is too low | The plant is becoming septic | There has been a reduction of solids in the aeration tank | The aeration tank is alkaline |
| Question - 3 of 14 | a | b | c | d |
| This could have been brought on by wasting too many solids to the storage tank. Sometimes it happens as a result of ; | Low return sludge flow rates | Solids being carried over the settling tank overflow weir | High return sludge flow rates | None of them |
| Question - 4 of 14 | a | b | c | d |
| This type of problem may be due to ; | Low dissolved oxygen concentration | Hydraulic underloading | Hydraulic overloading | Organic overloading |
| Question - 5 of 14 | a | b | c | d |
| A color change from dark brown to light brown may also be an indication that ; | The plant is becoming septic | Solids are accumulating in the settling tank and not being returned to the aeration tank | There is lack of dissolved oxygen in the aeration tank | None of them |
| Question - 6 of 14 | a | b | c | d |
| Solids accumulating in the settling tank could be due to ; | Clogged diffusers | Clogged surface skimmer | Clogged returned sludge air lift pump | None of them |
| Question - 7 of 14 | a | b | c | d |
| If the air lift pump is not the problem, another cause of solids not being returned to the aeration tank is ; | Excessive operation of the surface skimmer | Solids "hanging up" on the walls and baffles of the settling tank | Very little wastewater flow entering the plant | None of them |
| Question - 8 of 14 | a | b | c | d |
| When the color changes from dark brown to black, the treatment plant has ; | Accumulated too many solids | Had most of the sludge washed out of the plant | Become septic | None of them |
| Question - 9 of 14 | a | b | c | d |
| A septic condition is caused by ; | The loss of solids from the treatment plant | A lack of dissolved oxygen | Too high of a solids concentration in the aeration tank | The plant being hydraulically overloaded |
| Question - 10 of 14 | a | b | c | d |
| It is desirable to maintain the DO concentration in the aeration tank at a level ; | 1.0 - 2.0 mg / L | 2.0 - 3.0 mg / L | 3.0 - 4.0 mg / L | 0.1 - 0.2 mg / L |
| Question - 11 of 14 | a | b | c | d |
| The minimum DO concentration that should exists even during peak flow periods is ; | 0.1 mg / L | 0.4 mg / L | 0.5 mg / L | 0.3 mg / L |
| Question - 12 of 14 | a | b | c | d |
| When the DO concentration falls below 0.5 mg / L, you should ; | Add lime to the aeration tank | Decrease the rate of returning sludge | Increase the air supply to the aeration tank | Return to start - up procedure to get plant in running order |
| Question - 13 of 14 | a | b | c | d |
| The odor of the liquid in the aeration tank can be a good indication of the treatment plant condition. When the dark brown color develops, the liquid will have ; | An odor similar to dishwater | An earthy or musty odor | No odor | An odor similar to fresh grease or lard |
| Question - 14 of 14 | a | b | c | d |
| If an odor similar to that of rotten eggs develops and the liquid turns black, it is an indication that you should ; | Add lime to the aeration tank | Decrease the rate of returning sludge | Call the "Water Pollution Control Agency" | Increase the air supply to the aeration tank |
