May 2010, Vol. 22, No.5

Certification Quiz

Test Your Knowledge of Dewatering

    True or False Questions:
  1. Allowing anaerobic digester temperatures to drift more than 10°C (18°F) leads to difficult-to-dewater solids.
  2. Positive-displacement pumps are the best choice for feed pumps for biosolids and polymer dewatering equipment.
  3. Adding more polymer when using a belt filter press always increases cake solids concentration.
  4. Centrifuges dewater warmer solids better. In fact, tests have shown that for every increase of 5°C (9°F) in the temperature of the feed solids, the resulting cake solids concentration increases by 2 percentage points.

  5. Multiple Choice Questions:
  6. When decreasing belt speed on a belt filter press to increase cake solids concentration, how long should the system be allowed to stabilize before sampling?

  7. A. 5 to 10 minutes.
    B. 15 to 20 minutes.
    C. 35 to 40 minutes.
    D. 55 to 60 minutes.

  8. What action helps prevent a belt filter press from squeezing cake out from the lateral sides of the belts?

  9. A. Increasing belt speed.
    B. Increasing belt tension.
    C. Decreasing belt speed.
    D. Decreasing polymer dose.

  10. Which of the following actions will NOT help remedy high polymer consumption by a centrifuge processing viscous solids without sacrificing product quality? 

  11. A. Change the number and location of polymer addition points.
    B. Shorten the polymer aging time.
    C. Increase the amount of polymer dilution water.
    D. Switch to a different polymer.

  12. What is the effect of increasing the feed rate to a centrifuge? 

  13. A. Less power consumption.
    B. Better recovery if beyond design capacity.
    C. More total polymer use.
    D. Less total polymer use.

Questions developed by Steve Spicer and reviewed by the Association of Boards of Certification (Ames, Iowa) Validation and Examination Committee. 

Answer Key:
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Water Environment Federation (2008). Operation of Municipal Wastewater Treatment Plants; Manual of Practice No. 11, Sixth Ed. Alexandria, Va.: Water Environment Federation.

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