| With the rapid development of fowl-run intensification in china, chicken manure organic waste emissions increased rapidly. The composition of chicken manure is complex, with the characteristics of high solid percentage, high content of organics, nitrogen and phosphorus. If the chicken manure is not properly handled and then directly discharged into the environment, it will cause serious environmental pollution and endanger human health. Anaerobic fermentation is widely used in the treatment of organic waste because of the advantages of low power consumption, low sludge and odor production, and eliminating the pathogen, producing biomass energy. In the process of anaerobic fermentation, phosphorus(P) is released largely in the form of orthophosphate, if directly discharged into surface waters, it can lead to eutrophication at the high concentration of phosphorus. P is a kind of important mineral resources and chemical raw materials, but limited and nonreconerable resources, so the phosphorus recovery can realize phosphorus resource utilization.This thesis selects chicken manure as a typical representative to study the coupling technique of biogas production and recovery of phosphorus during anaerobic fermentation. As chicken manure has feature of low C/N, which easily result accumulation of ammonia nitrogen and organic acid to inhibit the action of the fermentation, a new process-three stage countercurrent fermentation process-is put forward, which can alleviate the inhibitory effect on microorganism fermentation, promote effective degradation as well as the rate of producing gas This study mainly compared three-stage countercurrent fermentation process with ordinary batch fermentation process in producing gas efficiency and phosphorus accumulation rate, studied sludge retention time (SRT) in three-stage countercurrent fermentation to produce biogas and phosphorus accumulation, using Terminal Restriction Fragment Length Polymorphism (T-RFLP) and Denaturing Gradient Gel Electrophoresisation (DGGE) to analyze the mechanisms of three-stage countercurrent process and microbial community structure, and discussed effects of pre aeration time on struvite method to recycle phosphorus in the fermented liquid nitrogen. In this paper, the research content is as follow.-(1) Compared with ordinary batch fermentation process, the three-stage countercurrent fermentation can significantly improve the efficiency of gas and the accumulation of phosphorus. Under the same condition of fermentation period, the production rate of biogas, methane cumulative and orthophosphoric by the three-stage countercurrent fermentation achieved 258 mL/(gVS),172 mL/(gVS) and 2.27 mg/(gTS) respectively,42%,64% and 54.6% higher than that of ordinary batch process. In addition, the three-stage countercurrent technique can also significantly increase the degradation rate of chicken manure, compared with ordinary batch type process, the TS and VS degradation rate increased by 24% and 25% respectively.(2) Different SRTs is studied to compare the gas efficiency and phosphorus accumulation in three-stage countercurrent fermentation process by chicken manure. When SRT is 9 d, the effect of biogas of three-stage countercurrent anaerobic fermentation was better. Productive rate of biogas and methane reached 385 mL/(gVS) and 258 mL/(gVS). And SRT for 9d and 11d, orthophosphate concentration both can be reached around 230 mg/L, higher than SRT for 5d. During three-stage countercurrent process, at SRT=9d, TS and VS of the substrate degradation rate reached 63% and 68% respectively, is meaningful for the pollution reduction treatment of chicken manure. Comprehensive comparative biogas productive efficiency and phosphorus accumulation concentrations, this paper choose the SRT for 9 d for anaerobic fermentation process by chicken manure in the follow-up study.(3) In order to provide basic data for the optimization of three stage countercurrent anaerobic fermentation process, the performance of biogas production in different stages was compared and the change of fermentation broth property was investigated. Results show that stage A1 and stage A3 are the keys to biogas production, release and accumulation of nitrogen and phosphorus, as well as degradation rate. Therefore, it is feasible to improve the performance of biogas production, accumulation concentration of nitrogen and phosphorus, and reductive production through the optimization of parameters in stage A1 and stage A3, such as concentration of chicken manure, property of inoculation sludge, and improvement of trace elements in nutrient solution.(4) According to the results of T-RFLP and DGGE, SRT=9d, the population structure of the microbial community is rich, has good uniformity. Rich in species diversity of the system is beneficial for the stability of ecological system. The advanced methane-producing bacteria mainly is Methanosaeta concilii strain, Methanoculleus marisnigri strain CoCam, Methanoculleus marisnigri strain JRI. The reactors all have methane-producing advantage bacterium which always exist or microbes strengthened, weakened and even disappeared during three stage countercurrent anaerobic fermentation process. At defferent SRTs, proportion of various advantage bacterium structure is also different.(5) The effect of pre-aeration time on phosphorus recovery from chicken manure fermentation with struvite method is studied. Results show that the performance of phosphorus recovery was equivalent in the group with pre-aeration treatment and the control group, which could reach about 98% for both of them. However, with the extension of pre-aeration time, the recovery efficiency of phosphorus with struvite method was higher. According to the analysis of SEM and XRD, the purity of MAP became higher along with the prolonging of pre-aeration time. When the pre-aeration time was 15 min, the purity of MAP reached 89.7%, which was 8.3% higher than the control group; the precipitation yield of struvite was 1.34 g/L, which was 15.5% higher than the control group. |
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