Study On Urban Sewage In Cold Areas Treament By SBBR Process Based On Simultaneous Nitrification And Denitrification

Urban sewage in cold areas is difficult to denitrify,and the traditional biological treatment process is difficult to operate steadily for a long time.Simultaneous nitrification and denitrification(SND)can produce nitrification,denitrification and carbon removal simultaneously in the same reactor,which fully proves the hypothesis that nitrification and denitrification can occur in the same environment,and is economical and environmentally friendly.However,in the low temperature environment,the microbial activity declined sharply,which made the effluent of the system unstable.Using biofilm filler can effectively enhance the capacity of the reaction system to treat urban sewage in cold areas.In order to achieve the standard treatment of urban sewage at low temperature,polyurethane biofilm filler was added to SBR reactor to construct a composite system of polyurethane biofilm filler and activated sludge.By analyzing the treatment effect of mature polyurethane biofilm filler and polyethylene biofilm filler on water distribution,the final filler used in the biofilm filler-activated sludge composite process(SBBR)was determined.Compared with polyethylene biofilm filler,polyurethane biofilm filler has larger specific surface area,and biofilm is easier to adhere to and grow on it.When it enters the reactor,it can quickly adhere to biofilm.The results showed that the effluent NH4~+-N and COD of the sewage treatment system with polyurethane biofilm filler were significantly higher than those of the sewage treatment system with polyethylene biofilm filler,and the average removal rates were 14.69%and 8.2%respectively.The results show that polyurethane biofilm filler has small pore and can be used as a good barrier to shelter the bacteria that have been attached to the growth and ensure that the bacteria grow in a good environment.A packed-enhanced SND reactor with aerobic activated sludge and polyurethane biofilm fillers was established to treat municipal urban sewage in a SBR reactor placed in a refrigerator.After 110 days of incubation,the concentration of NH4~+-N in effluent was maintained at 3~5 mg/L,and the removal rate of total nitrogen was74.45%.The results show that the denitrification capacity of the composite reactor for urban sewage has been greatly improved under the low temperature environment of 12?.By investigating the effects of different HRT,filling rate and temperature on the treatment of municipal urban sewage by SND intensification system,the treatment capacity of SND intensification process for municipal urban sewage in cold areas was further optimized.When HRT was 4 h,6 h and 8 h,the average concentration of NH4~+-N and TN in effluent was 8.05 mg/L,4 mg/L and 2.95 mg/L,respectively,and the average concentration of TN was 16.29 mg/L,13.25 mg/L and 11.01 mg/L.When filling rate was 50%,40%and 30%,the average concentration of NH4~+-N and TN in effluent was 4 mg/L,2.94 mg/L and 9.05 mg/L,respectively,and the average concentration of TN was 13.25 mg/L,11.03 mg/L and 16.17 mg/L.The average NH4~+-N concentration in effluent was 2.94 mg/L,19.18 mg/L,and the average TN concentration was 11.04 mg/L and 21.43 mg/L,respectively,when the temperature was 12?and 8?.The actual urban sewage was treated by SBBR reaction system.The concentration changes and removal rates of NH4~+-N,TN and COD in the influent and effluent were analyzed.In the first stage,50%simulated sewage and 50%actual urban sewage were mixed as the influent to gradually improve the system's direct adaptability to actual urban sewage.The removal rates of ammonia nitrogen and total nitrogen were reduced to 67.91%and 60.02%respectively.The concentration of NH4~+-N and TN in effluent reached 89.14%and 73.79%respectively by increasing the dissolved oxygen content in the reaction system step by step.In the second stage,the actual urban sewage was directly used as the reactor influent,and the removal rates of NH4~+-N and TN gradually decreased to 63.28%and 58.49%.Through constant regulation of drainage,the final removal rate of NH4~+-N and the average removal rate of TN can reach 89%and 74.45%,respectively.The influent COD fluctuated from 350 mg/L to 410 mg/L,while the effluent COD remained below 50mg/L.Microbial sequencing technology was used to detect the biofilm which had been domesticated for 20 and 110 days in low temperature environment.The characteristics of biofilm flora were analyzed at the level of bacterial diversity,phylum,class and genus.It was found that after 110 days of domestication,the activity of functional bacteria related to denitrification on biofilm was still good.