August 2009, Vol. 21, No.8

Certification Quiz

Test Your Knowledge of Residuals

    True or False Questions:
  1. T F Very high flows, such as a storm event, rarely affect dewatering.
  2. T F High BOD in plant influent makes no difference by the time the flow reaches dewatering.
  3. T F When dewatering or thickening a blend of primary and secondary sludge, the ratio of primary to secondary sludge determines the difficulty of dewatering.
  4. T F Thirty extra minutes of aging time improves polymer performance.
  5. T F After 7 days, polymer solution loses most of its activity and should be dumped.
  6. T F Drier cake always results in lower hauling and tipping costs at the landfill.

  7. Multiple Choice Questions:
  8. To what active concentration of polymer do vendors recommend diluting as-delivered polymer for dewatering sludge? 

  9. A. 0.2% active.
    B. 0.5% active.
    C. 1.0% active.
    D. 1.2% active.

  10. What is the minimum aging time recommended for dry polymers? 

  11. A. 15 minutes.
    B. 30 minutes.
    C. 45 minutes.
    D. 60 minutes.

  12. What is the minimum aging time for emulsion polymers? 

  13. A. 10 minutes.
    B. 30 minutes.
    C. 45 minutes.
    D. 60 minutes.

  14. At larger wastewater treatment plants, which of the following major dewatering costs is likely smallest? 

  15. A. Hauling and tipping.
    B. Polymer.
    C. Electricity.
    D. These are usually equal.

  16. When should the dewatering process be optimized?  

  17. A. Once, when the system is installed.
    B. Monthly.
    C. When costs or upstream processes change.
    D. Just before applying for a new land application permit.

Questions were developed by Peter LaMontagne with Peter LaMontagne P.E., (New Britain, Pa.). The Association of Boards of Certification (Ames, Iowa) Validation and Examination Committee reviewed the questions.

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

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