The Research Of Domestic Sewage Treatment Technology In Middle And Small Railway Station Areas

In this paper, on the basic of investigation and research on the existing middle and small railway stations in Northeast,Southwest and East of China, according to characteristics of sewage in China's railway station area and differences of geographical environment in different areas,it has proposed the "new energy-saving ecological wastewater treatment system" by combining new energy-saving technology with the traditional sewage treatment method.We has established medium-sized energy-saving wastewater treatment systems in Iron ASTRI Huairou test site, and used mathematical models to analysis and optimize the result of system's sewage treatment, proposed the boundary conditions of system running in different situations. Finally, this paper used AHP and fuzzy number method to make comprehensive benefit analysis for energy-efficient wastewater treatment system.The conclusions are as following:(1) According to the survey of actual situation,it can get the characteristics of sewage emissions in middle and small station area:①the inflow of sewage water is small and uneven, with many points and long line, pollution sources is dispersed;②wastewater quality better than normal municipal wastewater, the normal is:CODcr 50～220mg/L, ammonia nitrogen 10～50 mg/L, SS 50～200 mg/L;③the wastewater quantity and quality has two peak periods in one day, one is 11am to 14am, one is around 5 pm, the change is not large in the rest time,in the two time periods generally COD is 100～200 mg/L, ammonia nitrogen is 30～50mg/L, SS is 90～200 mg/L, wastewater quantity and pollution load at night is lower than the day, and after midnight Water quantity and pollution load is lower than early night.(2) Research and practice has proved that it is difficult to achieve the goal by a single ecological treatment process to deal with the the railway station sewage,the best technical solution should be new energy-saving eco-processing system has combination features of super deep anaerobic pond, aeration tank, constructed wetland bed. Super deep anaerobic pond in sewage treatment system has been desigend by 2m3/d flow, and each wetland unit is designed by 0.5m3/d flow, the size of the system structure and technical parameters are as follows:reservoir 1.5×1.5×1.2m; super deep anaerobic pond 1.1×10.7m; aeration tank 1×1×1.5m; horizontal subsurface flow constructed wetlands 4.5×2.2×1m; vertical flow constructed wetland 4.5×2.2×1.3m. (3) Studies have shown that main factors which affect the pollutants removal result of energy-saving sewage treatment system are time, temperature, organic load and oxygen demand. When the staying time t=1～2d, temperature T=6℃, the organic load F/M=4mg/L, oxygen demand R=39.658kg/h, the removal rates of system on COD, BOD5, NH4-N, SS were 97%,88%,93%,66%. When the staying time t=5～6d, the water temperature T=20℃, the organic load F/M=2mg/L, oxygen demand R= 39.656kg/h, the removal rates of system on COD, BOD5, NH4-N, SS removal rates were 99%,97.5%,97%,86%. The system's issue water achieved first standard of other sewage disposalunits in "Integrated Wastewater Discharge Standard" (GB8978-1996)(4) Using AHP and fuzzy number method for research, according to the linear weighting function Uj(x) to analysis and judge the benefit. The results show that wetland treatment system Uj(x)=0.7736 of the test site in Huairou, is ecological economic system which is running good, and its long-term benefits are remarkable.