Process and plant for waste water purification comprising dephosphorisation and anaerobic/aerobic treatment

摘要

Waste water is disposed in a flocculation mixing tank 1, an anaerobic tank 2 and an aerobic tank 3 connected in series. First, a dephosphorization flocculating agent and, if necessary, a polymeric flocculating agent are added to waste water in order to produce and grow phosphorus-containing flocs therein. Then, to the water is added a recycling solution from an aerobic tank 3, said solution containing nitrates and nitrites. The mixture water is charged in an anaerobic tank 2 until microbially decomposable components (herein referred to BOD components), nitrates and nitrites are anaerobically and microbially decomposed and gas is produced. In the aerobic tank 3 is charged a supernatant solution from the anaerobic tank 2, said solution containing ammonium compound and BOD components, to nitrates, nitrites and CO2. At least a part of supernatant solution containing the nitrates and nitrites is recycled to the anaerobic tank 2. Solids discharged from the anaerobic tank 2 and the aerobic tank 3 are wasted. Nitrogen compounds and phosphorus compounds as well as BOD components are removed from waste water. IMAGE