Which nitrogen form is used as a parameter in wastewater analysis for nitrogen content?

• A. Nitrate nitrogen
• B. Organic nitrogen
• C. Ammonia nitrogen
• D. Nitrite nitrogen

Answer: (C)

Nitrogen in wastewater shows up in several forms, but the parameter most commonly used to express nitrogen content is ammonia nitrogen. This form, encompassing both unionized ammonia (NH3) and ammonium (NH4+), is the one that’s readily available to microbes and directly drives the treatment steps of nitrification and denitrification. It’s also the primary inorganic form that poses aquatic toxicity and contributes to oxygen demand, so plants monitor and control it closely. Nitrate and nitrite are oxidized products that come later in the process and are usually tracked separately to evaluate the progress of nitrification/denitrification. Organic nitrogen is part of the broader total Kjeldahl nitrogen measurement, but ammonia nitrogen remains the standard single parameter for indicating nitrogen content in wastewater analysis.