In sewage treatment operation, there are a large number of carbon-containing organic matter and nitrogen-containing organic matter in sewage treatment. The former uses carbon, hydrogen, and oxygen as the basic elements. The latter uses nitrogen, sulfur, and phosphorus as the basic elements. Nitrogen containing organic matter will eventually be converted into inorganic substances such as ammonia nitrogen fertilizer, nitrite nitrogen fertilizer, nitrate nitrogen, water and carbon dioxide during aerobic decomposition. Therefore, the determination of the above three indexes in sewage treatment operation can reflect the decomposition process and the degree of inorganic treatment after treatment.
When only a small amount of nitrite nitrogen appears in the secondary sewage treatment plant, the treated water is not yet stable. When the oxygen is insufficient, most of the organic nitrogen in the sewage treatment operation is converted into inorganic substances, and the outflow water flows into the water body. It is relatively stable. In general, the ammonia nitrogen value of sewage entering the plant is about 30 to 70 mg / L. The water entering the plant generally does not contain nitrite and nitrate. Secondary sewage treatment plants in sewage treatment operations generally can not remove large amounts of nitrogen fertilizer. When the treatment level is high, some ammonia nitrogen can be converted into nitrate nitrogen.