Study On Optimization Of A~2/O Process Operation In Urban Wastewater Treatment Plant

In this paper,the A²/O process of a wastewater treatment plant of the North of China was taken as the research object.The general situation,the change of the actual influent and effluent volume,and water quality of the wastewater treatment plant were analyzed,and the key enterprises discharged into the wastewater treatment plant were investigated.The reasons were studied that the poor effect of nitrogen and phosphorus removal in operation of the wastewater treatment plant,factors of nitrogen and phosphorus removal using A²/O small-scale test device and proposed corresponding measures.The water quality,water quantity,production process and water treatment facilities of the key wading enterprises were investigated.The results showed that the COD_Crr concentration in the effluent was high,the drainage color of the clothing company was high,the chromium-containing wastewater was discharged by packaging material company,and has a effect on the water influent of the wastewater treatment plant.The effluent of COD_Cr,TP,NH₄⁺-N,TN concentration of the wastewater treatment plant were 70.51mg/L,1.05mg/L,42.29mg/L,60.98mg/L,and the effluent quality didn't meet Class A standard of the Pollutant Discharge Standard for Urban Wastewater Treatment Plants?GB18918-2002?.The possible reasons for the failure of the nitrogen and phosphorus in the wastewater treatment plant to reach the standard are as follows:the influent C/N of the wastewater treatment plant was relatively low,the carbon source and alkalinity was insufficient,and the nitrogen removal effect of the system was obviously reduced.The high redox potential and nitrate concentration in the anaeric zone,which affected the phosphorus removal efficiency.The mixed liquid was too large in reflux,and a large amount of dissolved oxygen was carried to the anoxic pool,which has a great impact on denitrification and poor nitrogen removal effect of the system.To solve the above problems,the optimization of operation test was carried out,study the A²/O process small-scale test and the corresponding optimization mesures were put forward.The ratio of carbon to nitrogen in raw water was controlled at about 5,the reflux ratio of mixture was adjusted to 200%,the dissolved oxygen was controlled below 0.20 mg/L,the aeration tank dissolved oxygen was controlled at about 2.5 mg/L,Through the above optimization measures,the effluent quality of the wastewater treatment plant was obviously improved.The the main pollutant effluent concentration COD_Cr,TP,NH₄⁺-N,TN index were 37.62 mg/L,0.45mg/L,9.06mg/L,15.74mg/L,the average removal rates were 85.30%,90.41%,87.39%and 82.07%,the effluent quality of the wastewater plant was improved,it provides theoretical support for stable operation of the wastewater plant.