September 2009, Vol. 21, No.9

Certification Quiz

Test Your Knowledge of Lab Practices

    True or False Questions:
  1. T F Consistently high blanks (>0.2 mg/L) can be an indication of poor quality source water (such as distilled water).
  2. T F When a wastewater treatment plant uses ultraviolet light to disinfect effluent, BOD and CBOD samples taken downstream from the disinfection point do not need to be seeded because bacteria in the effluent are not killed by ultraviolet light but rather are unable to reproduce.
  3. T F The conversion of ammonia (NH3) to nitrate (NO3-), a process that depletes dissolved oxygen in a sample, does not take place if a nitrification inhibitor is added to the sample in accordance with the method.
  4. T F The seed control bottle (used to determine the seed correction for seeded samples) must deplete at least 2.0 mg/L of dissolved oxygen to be considered valid.

  5. Multiple Choice Questions:
  6. What does the biochemical oxygen demand test measure in a wastewater treatment plant?

  7. A. The concentration of organic material in a waste sample.
    B. The concentration of organic material and reduced forms of nitrogen (e.g., ammonia) in a waste sample.
    C. The oxygen-depleting capacity of a waste sample.
    D. The dissolved-oxygen concentration of a waste sample.

  8. For which test or tests is it acceptable to store dilution water (source water to which nutrients and buffers have been added) in the BOD incubator?
  9. A. When testing BOD or CBOD.
    B. When testing CBOD, but not BOD.
    C. When testing BOD, but not CBOD.
    D. Only if testing ultimate BOD.

  10. When analyzing effluent BOD from a wastewater treatment plant that uses chlorine disinfection, which of the following reagents is the best choice to ensure excess chlorine is removed before proceeding with the test?

  11. A. Dilute sulfuric acid.
    B. Dilute sodium hydroxide.
    C. Sodium thiosulfate.
    D. Sodium sulfite.

  12. Which of the following options most likely provides the best source water from which to prepare dilution water for a BOD test?

  13. A. Distilled water put through deionization columns including an activated carbon filter.
    B. Purified drinking water purchased from a drugstore.
    C. Distilled water filtered using a 0.45 micron (e.g., fecal coliform) filter.
    D. Water taken from receiving waters at least 1000 m downstream from a wastewater treatment plant.

  14. What is the saturation point of dissolved oxygen in water dependent upon?

  15. A. Temperature, atmospheric pressure, elevation of the lab, and salinity.
    B. Temperature, atmospheric pressure, and salinity.
    C. Temperature and salinity only.
    D. Atmospheric pressure and salinity only

  16. Given the following data, what BOD should be reported for Sample A?

    Blank = 0.01 mg/L.

    Seed control average using 2 mL of seed = 2.0 mg/L.

    Volume of seed used in GGA and Sample A = 1.0 mL.

    GGA standard = 194 mg/L.



    DO on Day 1

    DO on Day 2


    5 mL

    8.80 mg/L

    4.50 mg/L


    10 mL

    8.80 mg/L

    1.80 mg/L


    15 mL

    8.80 mg/L

    0.90 mg/L

  17. A. 180 mg/L.
    B. 189 mg/L.
    C. 198 mg/L.
    D. 204 mg/L.

Questions were developed by Perry Brake, environmental consultant and retired manager of the Washington State Environmental Laboratory Accreditation Program.

Answer Key:
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The Association of Boards of Certification (Ames, Iowa) Validation and Examination Committee reviewed the questions.