Texas Wastewater Class B Practice Exam

Which of the following is NOT a nitrogen transformation process in the activated sludge plant?

1. Assimilation

2. Dissociation

3. Nitrification

4. Denitrification

The correct answer is: Dissociation

Dissociation is indeed not a nitrogen transformation process typically recognized in the context of activated sludge treatment. In wastewater treatment, particularly in activated sludge processes, nitrogen undergoes various transformations that are crucial for its removal and conversion into less harmful forms. Assimilation refers to the process where microorganisms incorporate inorganic nitrogen sources, like ammonium, into organic molecules, effectively contributing to biomass growth. This process is essential for microbial development within the system. Nitrification is the biological oxidation of ammonia to nitrites and then to nitrates, facilitated by specific nitrifying bacteria in the activated sludge. This process is significant because it converts ammonium, which can be toxic in high concentrations, into nitrates that can be further processed. Denitrification, on the other hand, involves the reduction of nitrates back to nitrogen gas or, in some cases, to nitrous oxide in anoxic conditions, where nitrates serve as an electron acceptor. This is crucial for removing nitrogen from the system, thus preventing its release back into the environment in a form that could cause problems, like eutrophication. The term dissociation typically relates to the process of separating molecules or ions in solution and is not recognized as a nitrogen transformation process in the context of activated sludge treatment.