Answer to problem 1.

1. Examine the following statements about denitrification:

  1. It is an anaerobic process
  2. It only occurs in the presence of a few specific species of microbes
  3. It involve chemical reduction
  4. It is invariably beneficial to the ecosystem of a receiving body of water.
  5. It involves nitrogen in compounds: NO3, NO2 and N2.

Which of the above statements are true?

  1. I and II
  2. I, III, and V
  3. I, IV, and V
  4. II, III, V

    B is the correct answer. I and III are basic: denitrification is anaerobic and is the reduction of NO3 to N2. V is a little trickier, the pathway for denitrification is NO3--NO2--N2. As for II, many species are capable of denitrification, not just a few. Which ones are present in a wastewater plant depends on the plant. As for IV, all receiving waters have some capacity to handle a nitrate load without adversely effecting the ecosystem. If that capacity is still unmet, denitrification offers no advantages.


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