Improvement Of The Process Of Denitrification And Phosphorus Removal In The Comprehensive Sewage Treatment Plant In Development Zone

It has great significance that denitrifying and dephosphorizing the mixed sewage in the plant with high proportion of industrial sewage,and upgrade the drainage quality to improve the water environment quality,and it also provides an important reference for the similar sewage treatment plant.In this study,the upgrading and reconstruction experiment of denitrification and dephosphorization was conducted in a sewage treatment plant located in Jiangyin development zone.We compared the operation effect and effluent indexes of before and after the modification,and explored the influencing factors of biological denitrification and dephosphorization.The research results enriched the technological connotation of denitrification and dephosphorization in a comprehensive sewage treatment plant in the development zone.In the experimental area,the industrial sewage is mainly discharged by enterprises（such as textile,printing and dyeing electronic circuit）,and domestic sewage is composed of local residents’domestic sewage and initial rainwater.the ratio of industrial sewage and domestic sewage is 9:1.‘Chemical phosphorus removal+anaerobic hydrolysis+A/B/C aeration+biological filter’process was adopted in the phase-Ⅰproject.The mean treated water volume was 16,000 m³/d,and the other effluent indexes basically meet the design standard except for the total phosphorus concentration.The water quality is as follows:the COD content is 32.40～125.8mg/L and its fluctuation range is 93.4mg/L,the BOD₅ content was4.6～16.0mg/L and its fluctuation range was 11.7mg/L,the TP content was1.0～5.0mg/L and its fluctuation range was 4.0mg/L,the SS content was10～44mg/L and its fluctuation range was 34mg/L,the p H was 6.3～7.4 and its fluctuation range was 1.1,and the DO content was 2.2～5.8mg/L and its fluctuation range was 3.6mg/L.The Secondary reinforcement technology of the simultaneous denitrification and dephosphorization combinated with the tertiary reinforcement technology of the deep processing was adopted in the phase-Ⅱproject.The improvement scheme of the sewage plant was the‘coagulation+filtration’technology.The treatment process was the‘efficient sedimentation tank+frame filter+uv disinfection’.Seven months after the operation of the upgrading and reconstruction project,the effluent indexes（such as COD,SS,TP,TN,NH₃-N）tends to be stable,and the concentration significantly decreased.The running was stable in the following three years.The concentrations of COD,NH₃-N,TP and TN stably reached the discharge limits of major water pollutants in the urban sewage treatment plant level key industries in Taihu Area（DB 32/1072-2007）ClassⅡof the emission standards.The indexes of BOD,SS,and p H stably reached pollutant discharge standard of urban sewage treatment plant（GB18918-2002）Level A.The operation parameters of the integrated sewage treatmen t line after the transformation are suggested as follows:NO₃^--N<1.5 mg/L in anaerobic environment controls anaerobic section,DO<1.5 mg/L in the operation of anoxic section strictly controls internal reflux,the applied carbon source dosage should be less than 5 mg COD/mg NO₃^--N,SV%should be controlled within 20-50%and SVI within 50-150 m L/g in aerobic operation,and 0.3‰PAFC added into the sedimentation tank.After the upgrading and reconstruction,the drainage quality of tail water the standard steadily,and the cost is increased by 0.17 yuan/m³.