Tennessee Wastewater Operator Practice Exam

Which process is primarily responsible for nitrogen removal in wastewater treatment?

1. Settling

2. Denitrification

3. Filtration

4. Coagulation

The correct answer is: Denitrification

Denitrification is a crucial biological process in wastewater treatment specifically aimed at removing nitrogen compounds. During this process, bacteria convert nitrates (NO3-) and nitrites (NO2-) present in the wastewater into nitrogen gas (N2), which is then released into the atmosphere. This transformation is vital because excess nitrogen can lead to problems like eutrophication in receiving waters, negatively impacting aquatic ecosystems. Denitrification generally occurs in anoxic conditions, meaning in the absence of oxygen, often in specific treatment stages such as in biological treatment systems or in engineered wetlands. The organisms involved in denitrification use the nitrate as an electron acceptor during the metabolic process when oxygen is scarce, effectively reducing nitrogen levels in the effluent. In contrast, settling primarily deals with the physical separation of solids from liquids in sedimentation tanks, filtration is aimed at removing suspended particles from the wastewater stream by passing it through porous media, and coagulation involves the addition of chemicals to aggregate and remove fine solids. Therefore, while all these processes play significant roles in wastewater treatment, denitrification specifically targets nitrogen removal, making it the correct answer for this question.