The majority of the nitrogen present in raw sewage is from urea and fecal material, although small amounts are found in some household cleaners. Nitrogen is an essential chemical element and nutrient for all life forms. It constitutes 78 percent of the atmosphere by volume and is present in surface water and groundwater as ammonia, nitrite, nitrate and organic nitrogen. Total nitrogen is the measure of the complete nitrogen content in wastewater including nitrate (NO3-), nitrite (NO2-), ammonia (NH3), ammonium (NH4+), and organic nitrogen (expressed as mg/L of N); all these forms of nitrogen, as well as nitrogen gas (N2), can
