A large-scale wastewater treatment plant operation experience and process control analysis in Zhengzhou

Abstract

Stable operation of wastewater plants under overload has been a hot spot of concern for researchers，and efficient nitrogen and phosphorus removal is a difficult point in the process of stable operation. A wastewater treatment plant in Zhengzhou uses a pre-anoxic modified A2/O process，treating 1.2-1.8 times the design value，with influent BOD5/COD，BOD5/TN and BOD5/TP ranges of 0.19-0.88，1.38-7.21 and 13.12-89.17 respectively，and uses multi-point distribution of influent，increased internal reflux ratio，precise aeration and other operation methods. The variation of nitrogen and phosphorus in the whole wastewater process was analyzed. The results showed that the removal rates of COD，TN and TP reached 90.4%，83% and 98.55%，which were better than the Class Ⅰ A discharge standard of the Pollutant Discharge Standard for Urban Wastewater Treatment Plants（GB 18918—2002）， when the influent water was evenly distributed in the pre-anoxic，anaerobic and anoxic sections，the internal return ratio was 400% and the DO concentration in the aerobic tank was below 0.5 mg/L.Some indicators reached Surface Water Quality Standard（GB 3838—2002） Class Ⅲ standard.

Keywords

• overload
• nitrogen and phosphorus removal
• wastewater treatment