Aerobic Biofilm Reactor With Semifixed Packing Treating Livestock Wastewater And Its Performance Assessment

With the rapid development of livestock and poultry breeding industry in China, the related environmental problems, mainly derived from the livestock wastewater, have become increasingly serious. Therefore, livestock wastewater must be treated to reduce its damage to environment. Based on comparison between different livestock treatment technologies, this study adopted a new treatment technology-the aerobic biofilm reactor with semifixed packing (ABRSP) to treat livestock wastewater, and explored its optimization craft parameters. Next, based on scenario analysis, this reactor was assumed to treat the livestock wastewater from the wastewater treatment plant with Anaerobic Baffled Reactor+Cyclic Activated Sludge System (ABR+CASS) craft, located in Sichuan Agricultural University-Yaan Campus, Yaan City, China, through replacing the original ABR and CASS reactors using this ABRSP reactor. And finally, the performances of the two crafts were preliminary compared using emergy synthesis and economic evaluation.Firstly, a serial of single factor experiments were carried out to decide on the optimal operation conditions for eliminating CODCr, TN and TP in the simulation wastewater, and the results were compared with these from the blank experiment which eliminates the microorganisms in the ABRSP reactor through high temperature pasteurization, to quantify the role of microorganisms in treating wastewater. Next, the microbial colony structure on the biofilm was identified by PCR-DGGE technology to analyze the related mechanism. And then the practical livestock wastewater was treated, under the optimized conditions, so as to test the adaptation of the reactor. Meanwhile, the comprehensive performance of the two scenarios (one is the ABR-CASS craft, and the other is ABRSP craft) was evaluated using the emergy analysis and economic evaluation, and the main conclusions are listed as follows.(1) The results from the single factor experiments show the optimal conditions for the ABRSP reactor:HRT 5 hours, influent CODCr concentration 1000 mg/L, and C/N ratio 20:1. Under these conditions, the removal rate of CODcr, TN and TP can reach 91.0% ±1.39%,93.3%±1.42% and 73.0%±3.65%, respectively. Accompanied by results from the blank experiment, it is found that biodegradation of microorganisms contribute 80.4% ±1.53%,88.1%±3.58% and 31.5%±5.21% to elimination of CODCr, TN and TP, respectively.(2) The results of the microbial identification indicate that the microorganisms in the biofilm belong to Bacteroidetes, Firmicutes, Proteobacteria, Acidobacteria and other unclassified groups. Therein, Proteobateria, including a-Proteobacteria,β-Proteobacteria, and y-Proteobacteria, are the most predominant phylum. And these microbes have important contribution to the removal of TN and TP.(3) The results from the practical livestock wastewater treatment show that the removal rates of CODCr, TN and TP can reach 94.0%±0.38%,86.0%±0.87% and 45.5% ±3.19%, respectively, under the optimized ones according to the simulation experiments. Compared with those results from the simulation experiment, the removal rate of CODCr increases by 3.0%, the removal rate of TN is reduced by 7.3% and the TP removal decreases by 27.5%, respectively. Generally this reactor has good adaption to the practical wastewater treatment.(4) Based on scenario analysis, the ABRSP craft is assumed to treat the livestock wastewater from the livestock wastewater plant with ABR-CASS craft, located in Sichuan Agricultural University-Yaan Compus, Yaan City, China. The comprehensive performances of ABRSP craft and the ABR-CASS craft are compared using emergy synthesis. The results show that the ABR-CASS craft has larger emergy inputs than the ABRSP craft does. The sequence of emergy flows for the two crafts are listed in a descending order, as follows:wastewater influent, local renewable resources, purchased renewable resources, purchased nonrenewable resources and local nonrenewable resources. For the two crafts, their wastewater emergy input is the same, but the other emergy flows are different due to their different characteristics. Therein, the ABRSP craft has the larger currency flow input than the ABR-CASS craft, and this leads to the slightly lower economic benefit of the former.(5) The ABRSP craft is more sustainable than the ABR-CASS craft from the perspective of environment. With the resource depletion and environmental problems, the former is more beneficial for social sustainable development.