In what four forms is nitrogen commonly found in wastewater?

Nitrogen is typically found in wastewater in various biochemical forms, each playing a significant role in the nitrogen cycle within treatment systems. The correct choice outlines the four most common forms: Organic nitrogen, Ammonia (NH3), Nitrite (NO2-), and Nitrate (NO3-).

Organic nitrogen is derived from proteins, nucleic acids, and other biological materials, mainly originating from human and animal waste. Ammonia is an important form of nitrogen in wastewater, often the result of the breakdown of organic nitrogen through the actions of microorganisms.

Nitrite and nitrate are intermediary and end products of the nitrification process, where ammonium is oxidized ultimately to nitrate through the specific actions of nitrifying bacteria. These forms are critical as they are involved in various biochemical processes, such as nutrient cycling and can have significant implications for water quality.

While the other choices mention nitrogen species, they introduce forms that either do not accurately represent the nitrogen forms commonly found in wastewater or include incorrect substances that are not prevalent in this context. Thus, choice A accurately captures the primary states of nitrogen around which wastewater treatment processes center.