January 2007, Vol. 19, No.1

Certification Quiz

Test Your Knowledge of Nutrient Removal

    True or False Questions:
  1. Nitrification is the two-step biological conversion of ammonia to nitrite and nitrite to nitrogen gas.
  2. Nitrosomonas is the name of the bacteria that converts ammonia to nitrite.
  3. Successful operation of an enhanced biological phosphorus removal system must have sufficient readily available organic carbon and phosphorus in the secondary influent.
  4. When relying solely on chemical phosphorus removal in a nitrification plant, the effect of the chemical addition on the alkalinity must be taken into account.
  5. The four iron compounds that can be used for phosphorus precipitation are ferrous chloride (FeCl2), ferrous sulfate [Fe(SO4)], ferric chloride (FeCl3), and ferric oxide (Fe3O3).

  6. Multiple Choice Questions:
  7. What is the name of the condition where Nitrobacter growth cannot keep up with Nitrosomonas growth, and effluent concentrations of nitrite increase?

  8. A. Short-circuiting.
    B. Reverse nutrient removal.
    C. Nitrite lock.
    D. Half-saturation.

  9. What temperature range promotes the optimum nitrification rate?

  10. A. 95°F to 108°F (35°C to 42°C).
    B. 50°F to 77°F (10°C to 25°C).
    C. 35°F to 41°F (2°C to 5°C).
    D. 35°F to 41°F (2°C to 5°C).

  11.  Why would methanol be added to separate-stage denitrification reactors?

  12. A. It increases dissolved-oxygen content.
    B. It provides a food source for the denitrifying bacteria.
    C. It partially disinfects the water.
    D. It reduces the number of denitrifying bacteria to enable young growth.

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

Answer Key:
Click here to show or hide the answer key


Water Environment Federation (2005). Biological Nutrient Removal (BNR) Operation in Wastewater Treatment Plants, Manual of Practice No. 29. New York: WEF Press McGraw-Hill.