Study On The Construction Of Nitrogen Removal Process Based On Combined Sewer Overflows With Low C/N And Its Estrogens Removal Behaviour

Combined sewer,whose overflows(CSOs)in rainy days has brought a series of problem to the environment,had been the most popular drainage in major city of China since the urbanization began.Though the sustainable development report has proposed that separate system must be used in construction of new urban,the existed combined sewer system is hard to transformation and upgrading,especially with high budget.The storage pond is the main method to intercept CSOs and transports it into wastewater treatment plant through sewage tube.Nevertheless,enormous overflow holes bring massive work quantity and high cost,large waste of source occurred in somewhere with low frequency of rainy,high dependence on topography strengthen the difficulty on collection and transportation,particularly in mountain city like Chongqing.Meanwhile,the concentration of estrogens up to ng/L in aquatic environment,such as CSOs,transforms the gender of fish contributed by the influence to vitellogenin.This study has constructed a process of nitrogen removal,which treats CSOs to satisfy the wastewater discharge standard and whose removal behavior on estrogens to reduce the risk of ecology,according to the analysis of the CSOs with low C/N intercepted by storage pond.The research results have shown below:(1)Corncob,in comparison with loofah,PBS,PCL,is more likely biodegraded by microbes.Dried corncob compared with corncob with alkali treatment has high biodegradability,which stems from tyrosine,tryptophan and aromatic protein,and will not release brown substance to influence water quality.Gross of matter has been released within 24 h in dried corncob,the stable static release rate after 24 h of COD is 4.83 mg / g·L·h.(2)The effect of TN removal: sponge iron>zeolite>quartz sand.The COD in effluent of sponge iron and quartz sand out of standard in some times,while never happened in effluent of zeolite.The accumulation of nitrite occurred in zeolite and quartz sand,whose concentration reach to 3.94 mg/L and 4.22mg/L,respectively.The color in effluent of sponge iron was black,but colorless in zeolite and quartz sand.(3)The better operation parameters in zeolite filter is HRT=1.6h,C/N=5.23-7.54.The effluent of denitrification unit has cost 8 days to satisfy the standard during biofilm culturing period,the accumulation of nitrite occurred in carbon source column and zeolite column,whose concentration up to 1.53 mg/L and 2.75 mg/L,respectively.5h operation after backwashing,the denitrification unit recovered.(4)Immobilized bacteria domestication under 10-15? cost 16 days,the removal rate of ammonia is 84%.The process of nitrogen removal was made up of nitrification unit,denitrification unit and filtration unit,the majority removal of ammonia was happened in nitrification unit,who contributed 74.45%,the massive removal of nitrate was arisen in denitrification unit,whose removal rate is 64.02%.The TN and COD in effluent of this process is 8.73mg/L and 26.78mg/L,respectively,which below the A level of standard.The fitting denitrification dynamic constant of carbon source column and zeolite column is 0.1298 and 0.0586.The removal rate of E1,E2,EE2 in this process is 60-70%,90%,80%,which can run stably after 12 days.7 days may cost to recover this process after 30 days paused.(5)Actual CSOs has little influence on such process,61.52% of COD in influent biodegraded by nitrification unit and white biofilm formed on immobilized bacteria simultaneously.The removal of TN was taken place in carbon source column,the removal quantity in carbon source column has occupied 70.94% in the whole process.The removal rate of TN in the whole process with actual CSOs is 63.03%,which blows 70.28% with artificial water distribution.The biodegradation of corncob increased the concentration of SS in zeolite column,SS was most removed in zeolite column and filtration unit,the SS of effluent in this process is 4.63 mg/L.A large amount of estrogens was degraded in nitrification unit,in the meantime,the concentration of estrogens in effluent was lower than limit of quantitative as a result of adsorption and interception of corncob,zeolite and quartz sand.