Research On The Effect Of Nitrogen And Phosphorus Removal From Polluted River-water By Inverted A~2/O Process

Urban rivers play an important role in urban living and city economy. When rivers are polluted, it will cause the deterioration of city environment and ecological imbalance; hence limit the development of city economy. Shenzhen River is a boundary river between Hong Kong and Shenzhen, and is of great significance to both cities. Buji River is the upstream branch of Shenzhen River which is heavily polluted due to the area's economy development. 50% pollution of Shenzhen River comes from Buji River. As a result, the treatment of Buji River becomes extremely urgent.This experiment adopted inverted A2/O(Anoxic/Anaerobic/Oxic)process reactor to carry out the treatment of polluted Buji River. Inverted A2/O process is a pre-denitrification technology; it strengthens the ability of nitrogen removal. Inverted A2/O process reactor is suitable for the treatment of southern river water with lower ratio of carbon to nitrogen. The operation parameters of the reactor are: hydraulic retention time (HRT) is 11h, sludge retention time (SRT) is 22d, inner recycling ratio is 200%, sludge return ratio is 75%.Results of the reactor running experiment show that: Effluent COD concentration is below national wastewater discharge gradeⅡstandard(100 mg/L) according to discharge standard of pollutants for municipal wastewater treatment plant GB18918—2002, and under most conditions, it is below national gradeⅠB standard (60 mg/L). The average removal rate of COD is 70.6%; Effluent BOD5 concentration is below national wastewater discharge gradeⅠB standard (20 mg/L), and the average removal rate of BOD5 is 91%; Effluent TN concentration is below national wastewater discharge gradeⅠB standard(20 mg/L), and the average removal rate of TN is 44%; Effluent TP concentration is below national wastewater discharge gradeⅡs tandard (3 mg/L), and the average removal rate of TP is 46.6%. In a word, the inverted A2/O process reactor performs well in treating the polluted Buji river water.An experiment was carried out on six heavy metals, Ni,Cu,Zn,Pb,Cr and Cd. Each heavy metal has a different effect on the reactor. The results indicate that: chromium chloride affects effluent COD concentration a lot; copper sulfate has certain influence on effluent ammonia nitrogen concentration; lead acetate and chromium chloride have a great impact on effluent TP concentration; cadmium chloride and copper sulfate affect effluent turbidity greatly. The result shows that, the reactor will turn to normal no matter which heavy metal affects.