Nitrate and nitrite are most often measured using a colorimetric method, which means the color of treated sample reflects the concentration of the parameter. This test can be done visually, comparing the treated sample to a set of reference colors. However, it is more accurate to use an electronic colorimeter, which uses a light source and a photodetector to find the concentration based on how much light is absorbed by the sample. The volume of acid required to change the color of the sample reflects the ammonia concentration of the sample. The more acid needed, the more ammonia in the sample.
Ammonia is the least stable form of nitrogen, so it can be difficult to measure accurately.
The proportion of unionized ammonia can be calculated, using formulas that contain factors for pH and temperature. Effluent Human waste is significant contributor of nitrogen to water. Ammonia, nitrite, and nitrate are decomposition products from urea and protein, which are in human waste. Ammonia is an ingredient in many household cleaning products and is sometimes used to remove carbonate from hard water. Nutrients in sewage effluent have been among the primary targets of pollution-control legislation, beginning with the Clean Water Act in 1972.