| With the constant development of small towns, the water emission of small town increase rapidly. Because of lack of appropriate technologies, the environmental problems caused by indiscriminate discharge of small town wastewater have become increasingly prominent, so the study on wastewater treatment technologies of small town is getting hotter. Based on the characteristics of domestic sewage in small towns, the multi-media bio-contact oxidation process for treatment of domestic sewage was selected in this paper. The effluent intended for urban greening.The appropriate parameter of biological contact oxidation in laboratory test, the three-dimensional fluorescence spectroscopy (3DEEM) characteristics of influent and effluent as well as properties of biofilm were studied, the following results were obtained through the research:there is about two weeks for the reactor to format biofilm, when the water temperature is between16℃and 32℃, HRT=12h, DO is 5-6mg/L, the removal rates of COD, NH4+-N, TN and TP are 75.8%,71.8%,45.9% and 35.7% respectively, each quota of the treated water meets the quality standard of urban greening in wastewater reuse(GB/T 18920-2002). There are aromatic protein I and aromatic protein II, microbial Metabolite and fulvic acid fluorescent peak in the three-dimensional fluorescence spectroscopy of sewage. Filamentous bacteria are skeleton and internal cocci and channel is visible in Biofilm. The dehydrogenase activity of biofilm can be affected by operation parameters.The optimum operation parameters, the 3DEEM and ultraviolet spectrum characteristics of wastewater, EPS characteristics and dehydrogenase activity of biofilm as well as the influence of DO and exchange water volume on EPS were studied, when the room temperature is between 28℃and 40℃, the best parameters of reactor are anaerobic time=4h, aerobic time=7-8h, the ratio of change water volume=1/2, when C/N ratio is 5.6, the removal rate of TN is up to 50%, the TN concentration for effluent is 13.9mg/L. organic compounds of B areas in sewage are more easy to degradate, and organic compounds of c, d, e areas are hard to degradate. the change of related substances can be shown from ultraviolet spectrum of wastewater. The content of EPS and dehydrogenase activity in the system are changing when DO; the organic matter; aerobic, anaerobic microbial metabolic activity are changing, aromatic protein I, aromaticity protein II, microbial and humic substances could be found in composition of EPS.Comparing this two operation modes, it can be seen that the effluent TN concentration in contact oxidation process is 53.6mg/L, and 37.5mg/L in SBBR in the case of pollutant concentrations of raw water are similar, which indicates that changing operation modes can reach rise of nitrogen removal efficiency.When the water flow is 1-2m3/d, The removal rate of COD, ammonia nitrogen and TP are not affected by reduce of temperature, but the removal rate of TN is decreased. The average effluent concentration of COD, NH4+-N, TNand TP are 28.2mg/L,0.4mg/L,15.4mg/L and 1.7mg/L respectively, which meets the quality standard of urban greening in wastewater reuse (GB/T 18920-2002). Except TP, the water quality indexes have reached the level B standards of urban sewage treatment plant emission (GB/T 18918-2002). |
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