| In China, the livestock and poultry breeding wastewater has been bringing about increasingly serious harm to the environment and human health. At present, most of the wastewater is discharged without any treatment. The existing treatment processes have not been popularized widely due to their low removal rate or high cost.Aerobic biofilm reactor has gathered extensive attention because of its high performance, small floor space and easy operation. Aerobic biofilm reactors can be divided into fixed bed and fluidized bed according to the status of carriers they used. In our research we applied the semifixed polypropylene tubes in aerobic reactor. Firstly, good-appearing biomembranes were bestrewed on these carriers through sludge domestication. Then three sets of single factor experiments (the water temperature, the C/N ratio and the CODCr loading of simulated wastewater) were designed based on the properties of real livestock wastewater. Processing parameters were optimized by determining the removal rates of various substances in the sewage at different HRT. Finally the practical performance was examined through treating real livestock and poultry wastewater.Batch inflow, intermittent circulation and continuous aeration were employed during the course of experiment. Changes of different forms of nitrogen, pH and DO values were determined at different HRT when the simulated wastewater was fed. The biofilm samples were collected and subjected to microbiological analysis. The seperated and purified dominant bacterias were authenticated after plasmid DNA extraction, PCR amplification for16S rDNA and sequence analysis based on the NCBI database, which provided better understanding of the process mechanisms of various pollution substrates in the reactor. The research shows:(1) In aerobic biofilm reactor with semifixed carriers, the floating carriers were evenly dispersed in the reactor, which avoided bottom blocking by the sinking of heavier carriers. Besides, the interaction among the carriers, water and air flows could enhance the biofilm renewal and activity, and reduce the energy consumption. The average biomass (dry weight) of membranes accumulated on the carriers was total up to75g/m2.(2) The COD removal rates were ca.90%at HRT=8h for both simulated and real livestock wastewater when the water temperature was20～35℃, the C/N ratio was5-20and the COD loading was500～4000mg/L.(3) At the level of C/N=20:1, the removal rates of NH4+-N and TN were the highest (Removal rates of NH4+-N>95%and removal rates of TN>90%at HRT=8h); however, their removal rates would decrease when C/N ratio deviated from20:1. The removal rates of NH4+-N and TN were>70%when the C/N ratio was between5and10; the removal rates decreased to nearly60%when the C/N ratio was increased to40.(4) In the experimental design with higher water temperature, lower C/N ratio and higher COD loading, the removal rates of TP were relatively high. Under the condition of the water temperature30～35℃, the C/N ratio5-10, and the COD loading2000～4000mg/L, removal rates of TP were kept50～90%at HRT=8h.(5) In aerobic biofilm reactor with semifixed carriers, the main denitrogen path was simultaneous nitrification and denitrification under the condition of various temperatures, C/N ratios and COD loadings, and the ESND was up to98～100%.(6) The different colonial morphologies on the culture medium showed that at least20kinds of bacteria were present in the reactor. The dominant bacteria were Pseudomonas fluorescens, Lysinibacillus fusiformis, Bacillus, Aeromonas respectively by16S rRNA sequence analyses and biochemical tests, among which Pseudomonas fluorescens was typical denitrifying and phosphate accumulating bacteria. |
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