Study On Deep Treatment Of Low C/N Ratio Domestic Sewage Based On Fe-C Micro-electrolysis Carrier And Biological Processes

With the increasing living standards of the people and the deepening of the urbanization process,the amount of water in the urban sewage has gradually increased,the complexity has increased,and many domestic sewage have shown a trend of low carbon-nitrogen(C/N)ratio.At the same time,the increasing importance of environmental issues has led to an increase in the discharge requirements for domestic sewage treatment plants.As a result,traditional urban sewage treatment processes are increasingly unable to meet the requirements.Urban sewage treatment plants have limited capital resources and are extremely sensitive to operating costs.Therefore,for urban sewage treatment plants with low C/N ratio,it is necessary to explore a high-efficiency energy-saving,low-cost,no secondary-pollution,simple and stable effluent is imminent.In this paper,aiming at the problems existing in the traditional low C/N ratio urban sewage treatment,the Catalytic iron-carbon micro-electrolysis carriers(CIA-MEC)independently researched and developed by this research group are used as the fillers.By combining catalytic microelectrolysis and biological treatment,the iron matrix coupled biological carriers are proposed to handle low C/N is the new process of A/O(anoxic/aerobic)domestic sewage.Through the whole aerobic activation method,the process was successful in 59 to 67 days.The total nitrogen in the effluent was 20.32±1.73 mg/L,and the average removal rate of total nitrogen was 73±1%.The effects of this process on different dissolved oxygen,reflux ratio,and Hydraulic Retention Time(HRT)were studied,and the most suitable operating conditions for the process were established:the dissolved oxygen was about 3.5 mg/L,and the reflux ratio was 5.5:1.The HRT of the anoxic reactor was 4 h,the HRT of the aerobic reactor was 6 h,and it was continuously operated under the optimum conditions.The mean value of total nitrogen in the effluent was 8.92 ± 2.94 mg/L,and the average denitrification efficiency of the system was 87±4.%,effluent COD was 21.20±10.52 mg/L,average COD removal rate was 88±6%,TOC average removal rate was 84±7%,effluent total phosphorus concentration was 0.20±0.11 mg/L,average removal rate was 94±2%.SPASS correlation analysis results show that the system has strong resistance to TN and COD load shocks.At the same time,the average pH of the anoxic reactor in the system is 8.03±0.16,and the average pH of the aerobic reactor is 7.39±0.29,which can meet the requirements of nitrification and denitrification.The indicators of the water discharge can all meet the national Grade A standard of "Water Pollutant Discharge Standard of Urban Wastewater Treatment Plant"(GB18918-2002).The analysis of the microbial communities at different locations and carriers within the experimental device shows that different types of carriers and differences in environmental concentrations within the system can cause significant differences in the composition of microbial communities at different locations within the system;iron-matrix coupled biological carriers have many The growth of functional bacteria associated with denitrification has a significant promoting effect also can increase the overall biomass.There are iron oxidizing bacteria with Fe2+ as an electron acceptor,Thiobacillus,Ferritroplicum.Acidovorax and other genus to Fe3+ in anoxic reactors.The electron donor Geobacter showed that there was an iron circulation system inside the anoxic reactor with iron as the electron transfer medium,autotrophic and heterotrophic bacteria.In this system,especially on the surface of iron-matrix coupled biological carriers,a large number of autotrophic denitrifiers occupy a competitive advantage.Thiobacillus,an autotrophic denitrifier,is the dominant genus in the denitrification process of this system,and it is also the most abundant in anoxic reactors.The dominant bacteria account for an average of 31.16%of the overall abundance in the anoxic reactor sample and up to 42.91%in the iron matrix carrier sample at the bottom of the anoxic reactor.The kinetics of the denitrification process in the anoxic reactor was studied.The kinetic model was as follows.The correlation coefficient reached 0.90233.C=QCNO3-/0.0065AhCNO3-+QThrough the analysis of the operating cost of the process,the process can be used as a reference in the actual project with a running cost of 1.14 yuan/ton.The operating costs are lower than the sewage treatment plants currently operating in accordance with the secondary emission standards.The research and development of this technology can provide new ideas and new technologies for the urban sewage treatment plant to raise the standard transformation,deep nitrogen and phosphorus removal,and thoroughly solve the problems of low C/N ratio domestic sewage.