| Question - 1 of 6 | a | b | c | d |
| The operation log shows the color of the liquid in the aeration tank has changed from dark brown to a light brown and the amount of solids in the 30 - minute settleability test has decreased from 300 mL to 50 mL and the settling tank has become cloudy. The indications show that ; | The plant is in good operating condition | The walls and baffles of the settling tank need scraping | The air blower is not working properly | Return sludge air lift pump is not working properly |
| Question - 2 of 6 | a | b | c | d |
| A corrective action to take would be ; | Remove the air lift pump from the tank for cleaning | Back flush the air lift pump | Rod out the air lift riser and sludge return line | The walls and baffles of the settling tank need scraping |
| Question - 3 of 6 | a | b | c | d |
| This was the correct action, but it failed to clear the stoppage. Your next action would be ; | Switch operation to the stand - by air blower | Remove the air lift pump from the tank for cleaning | Rod out the air lift riser and sludge return line | The walls and baffles of the settling tank need scraping |
| Question - 4 of 6 | a | b | c | d |
| This was the correct action, but it failed to clear the stoppage. Your next action would be ; | The walls and baffles of the settling tank need scraping | Switch operation to the stand - by air blower | Remove the air lift pump from the tank for cleaning | By - pass the plant |
| Question - 5 of 6 | a | b | c | d |
| After an air lift pump failure has been corrected, it is good practice to scrape the walls and baffles to help restore normal operations. Although back - flushing is an effective and simple means of clearing a clogged air lift, there is some preparation and care necessary. Which of the following is not an important consideration when back - flushing is done ? | The valve in the air lift discharge piping downstream of the flushing connection must be closed | The source of the water, when water is used | The rate of flow of the influent wastewater | The possible septic condition of the accumulated sludge in the settling tank |
| Question - 6 of 6 | a | b | c | d |
| Rodding and back - flushing, although requiring less work than the removal of the air lift, have certain limitations. Which of the following is not one of those limitations ? | Little or no knowledge of the cause of clogging is gained | The degree to which the clogged opening has been cleaned is never known | They are effective only for short (less than 3 m) air lift riser pipe lengths | They generally provide only partial and temporary solutions to the problem |
