Study On The New Technology Of BCO+SBBR Aerobic Treatment For Scaled Pig Farms Wastewater(Biogas Slurry)

With the rapid development of large-scale breeding industry, excrements of livestock and sewage discharge have increased continuously, which threatened the water safety of rivers and lakes. The environmental pollution caused by the pig industry has become an important pollutant source after industrial pollution. Since it has great influence on ecology and environment, it is necessary to put forward effective disposal methods. At present, the biogas slurry after anaerobic treatment of most large-scale pig farms which could not meet the discharge standard needs further research and development of aerobic post-processing techniques and crafts. Analyzing the reasons why the aerobic post-processing effects of anaerobic biogas slurry in the waster water of pig farms are bad; exploring the methods of improving the aerobic post-processing property for biogas slurry; developing the new effective craft of aerobic treatment for swine waste water; establishing proper and effective design approaches and engineering commissioning simulation and prediction model for aerobiont bioreactors. The study found that:1. Regarding electron transfer system(ETS)activity as the index and using triphenyl tetrazolium chloride(TTC)and iodo nitro tetrazolium chloride(INT)as the electron acceptor, the research on biological activity TTC-ETS and INT-ETS of aerobic sludge in SBBR and comprehensive toxicity IC50( half inhibiting concentration)of heavy metal and antibiotics on aerobic micro-organisms has been carried on. Single Cu(Ⅱ), Zn(Ⅱ)and Cr(Ⅲ)and single OTC, CTC and TC have inhibiting effects on aerobic sludge TTC-EST and INT-EST. With the concentration increase, the inhibiting percentage enhances. IC50 ranks as the following: IC50(Cr-TTC)>IC50(Zn-TTC)>IC50(Cu-TTC), IC50(Cr-INT)>IC50(Zn-INT)>IC50(Cu-INT), the toxicity of Cu(Ⅱ)on the aerobic activated sludge is the strongest; IC50(OTC-TTC)>IC50(TC-TTC)>IC50(CTC-TTC); IC50(OTC –INT)>IC50(TC-INT)>IC50(CTC –INT), the toxicity of CTC is the strongest; the unified expression of the influence for the union of different concentrations of Cu(Ⅱ), Zn(Ⅱ), CTC and OTC on the inhibition ratio of TTC-ETS and INT-ETS activity is antagonism.2. Researches on the single effect, compound effect and combined effect of heavy metal(Cu(Ⅱ), Zn(Ⅱ)and Cr(Ⅲ))and antibiotics(OTC, CTC and TC)in SBBR treatment on the waste water(COD, NH3-N, TN and TP)in the pig farms have been carried on respectively. Finally, the selected heavy metal-antibiotic combination has been put into BCO+SBBR treatment system; and its actual treatment effects have been studied. Single effects would have influence on the average removal rate and relative inhibition ratio of COD, NH3-N, TN and TP. With the concentration increasing, the influence would be enhanced. While the compound effect and combined effect are less than single effects, all the effects could present antagonism. Putting the same heavy metal–antibiotic combinations into SBBR equipment and BCO+SBBR equipment respectively and making a comparison, the results show that the treatment effect of BCO+SBBR is obviously better than that of SBBR.3. According to the probability theory, using residence time distribution(RTD)density function t E)( and residence time distribution(RTD)function t F)( to describe the back-mixing degree of pollutant infinitesimal in the running system quantificationally. The design model of practical reactor BCO has been deduced:(1)Adopting the continuous stirred tank reactor( CSTR) : ;(2)Adopting the tandem N-step CSTR(continuous stirred tank reactor): , effective reactor volume is: ; the design model for the SBBR practical reactor is: , the required time for each batch of operation is: tTotal=t + t0, that is the effective volume of reactor is: V=v0tTotal=v0(t + t0).4.Established the swine wastewater(biogas slurry)BCO + SBBR aerobic treatment technology. With the manner of phased progressive increase of waste water concentration, sludge was carried out in the BCO and SBBR. After the cultivation and domestication of inoculated sludge for 40 days, the reactor domesticated successfully.SBBR add 30% raw water and then taken to increase the C/N ratio, SBBR effluent COD, NH3-N and TP removal rate reached 66%, 67% and 59%,respectively. The BCO + SBBR combination aerobic process during normal operation, daily processing wastewater quantity is 150 m3 /d, the average COD, NH3-N, TP removal rate reached 82.5%, 94.1%, 78.5%. After artificial wetland treatment, the effluents are better than the standard values stipulated in the Pollutant Discharge Standard for Livestock and Poultry Industry(GB/T18596-2001).5. Neural network has been introduced to effluent quality prediction of aerobic treatment processing on the swine waste water. It establishes neural network model by regarding the effluents of acidification regulating reservoir and BCO as the input variables and regarding effluent of SBBR as the output variable. PSO algorithm has been brought in to optimize the weight of BP neural network. Thus, PSO-BP mixed model has been established. Then a comparison between PSO-BP mixed model and traditional BP model has been made. The models evaluation results show that during the training period and verification period, the Re%,R2 and NSE of COD are 3.51, 0.95, 0.93 and 4.22, 0.96, 0.92; the Re%, R2 and NSE of NH3-N are 2.15, 0.96, 0.93 and 4.16, 0.95, 0.94,simulation precision of COD and NH3-N is relatively high, and it shows well simulation effects. Meanwhile, it shows that the convergence rate and generalization ability of PSO-BP mixed model are better than those of traditional BP model by comparing PSO-BP mixed model and traditional BP model.