| # | A diffuser is what? | a device to measure dissovled oxygen. | a device to measure carbon dioxide content of aeration basins. | a device to concentrate sludge. | a device to break the air stream into fine bubbles. | none of the above | 4
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| 1 | When organic wastes are discharged to receiving water, oxygen is depleted by | algae during the day | bacteria. | ducks. | limestone rocks. | none of the above. | 2 |
| 2 | Which indicates a good quality domestic activated sludge? | black color and septic odor. | brown color and musty odor. | brown color and lots of dark brown foam. | settleability of 900 mls in a 1000 ml sample over 30 min. | none of the above. | 2 |
| 3 | Common settling times in wastewater treatment plants range from | 15 to 30 minutes. | 30 to 45 minutes. | 1 to 2 hours. | 2 to 4 hours. | none of the above. | 2 |
| 4 | In which of the following types of wastewater would settling occur most rapidly? | cold wastewater. | old (stale) wastewater. | septic wastewater. | strong wastewater. | none of the above. | 1 |
| 5 | Settled activated sludge is generally __________ than raw sludge. | thinner. | thicker | saltier. | denser. | none of the above. | 1 |
| 6 | Which of the following operational controls are used in the activated sludge process? | aeration, wasting, recirculation. | loading rate, solids concentration and dissolved oxygen. | recycling rate, blower speed, sludge age. | all of the above. | none of the above. | 2 |
| 7 | If the sludge depth in a secondary sedimentation tank is too high, what will happen? | decrease turbidity in effluent. | return activated sludge will have lower oxygen demand. | settleable solids from aeration tank will increase. | sludge may become septic. | none of the above. | 4 |
| 8 | An active sludge in the aeration tank with an abundant available food supply will have a relatively | high oxygen uptake and fast settling rate. | high oxygen uptake and slow settling rate. | low oxygen uptake and fast settling rate. | low oxygen uptake and slow settling rate. | none of the above. | 2 |
| 9 | Results of the settleable solids test run using imhoff cones may be used to | calculate the Imhoff settling index (ISI). | calculate the pounds of solids pumped to the digester. | indicate the quality of thefinal effluent. | all of the above. | none of the above. | 2 |
| 10 | What problems are created when the sludge build-up on the bottom of the sedimentation basin becomes too great? | degradation of process efficiency will result. | localized high flow velocities will be produced. | sludge scouring will occur. | all of the above. | none of the above. | 4 |
| 11 | Jar tests may be used to determine the optimum dosage of | alum. | BOD. | oil and grease. | volatile acids. | none of the above. | 1
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