Study On Improving Quality And Efficiency Of By-Products Of Anaerobic Fermentation Of Corn Straw

With the continuous development and rapid growth of the number of biogas projects in my country,the comprehensive utilization of（biogas slurry and biogas residue）has become a hot issue in today’s research.The biogas slurry and biogas residue after anaerobic fermentation has high fertilizer value.However,direct return to the field may cause problems such as increased soil salinity and accumulation of polycyclic aromatic hydrocarbons,causing potential risks to the soil environment.There are problems such as complicated application operation and low utilization rate.Therefore,the pollution-free treatment of biogas slurry and biogas residue and the improvement of quality and efficiency have become urgent problems to be solved in large-scale biogas projects.Based on this,this paper uses the biogas slurry and biogas residue produced by the corn straw biogas project as the experimental raw materials.The biogas slurry is filtered by a microfiltration membrane and adsorbed by biochar and then returned to the anaerobic fermentation system.High temperature aerobic composting is carried out for the turbidity of anaerobic fermentation to realize the improvement of quality and efficiency of anaerobic fermentation waste resource utilization.The biogas slurry filtered by the microfiltration membrane and adsorbed by biochar was returned to the anaerobic fermentation system to explore its effect on the gas production characteristics;the effect of adding biogas residue to the biogas slurry turbidity on the composting process was studied.The purpose of this study is to promote the high-value utilization of anaerobic fermentation residue resources through biogas slurry reflux and biogas residue composting,and to provide a theoretical reference for the high-value utilization of anaerobic fermentation residues.The main research contents and results are as follows:（1）Use four pore size PES（polyethersulfone）microfiltration membranes of 0.65μm（S1）,1.20μm（S2）,3.00μm（S3）,and 5.00μm（S4）to filter the biogas slurry.The filtration effect of suspended solids),COD（chemical oxygen demand）and ammonia nitrogen.The results showed that the retention effect of S1 was the best,and the content of SS,COD and ammonia nitrogen in the permeate obtained by S1filtration was the lowest,which were 81.23%,44.19%and 22.46%lower than that of CK,respectively.（2）Biochar was added to the biogas retentate obtained by S1 treatment according to 4g/L（K1）,7g/L（K2）,10g/L（K3）,13g/L（K4）for adsorption,and the different additions were explored.The adsorption effect of biochar on SS,ammonia nitrogen and COD in biogas slurry retentate.The results showed that all treatment groups had certain effects on SS,COD and ammonia nitrogen,which were reduced by5.62%-11.93%,23.28%-32.35%,and 2.55%-5.64%,respectively.（3）Sequencing batch type biogas slurry reflux anaerobic fermentation experiment was used to explore the effect of four levels of biogas slurry retentate supernatant reflux on the gas production characteristics of the anaerobic fermentation system.The results showed that,compared with CK（without biogas slurry reflux）,the gas production peak of the treatment groups（T1-T4）with biogas slurry return was 1 day earlier,and the cumulative methane production and the maximum daily methane production were both increased by,0.24%-26.46%,9.34%-42.54%.The modified Gompertz model was used to fit the data（R²>0.98）,indicating that the supernatant reflux of biogas slurry retentate can shorten the lag period of anaerobic fermentation by 0.5-0.79d.Comprehensive analysis shows that T2（the supernatant reflux treatment group after adsorbing the retentate at the addition level of 7g/L biochar）can achieve the maximum daily methane production(39.20 m L g VS^-1)and cumulative methane production(137.14 m L g VS^-1).（4）The biogas slurry turbidity produced by the adsorption of biogas slurry with four different amounts of biochar was added to the aerobic compost using biogas residue as raw material,and the effect of adding biogas slurry suspension to aerobic composting of biogas residue was explored.The results show that the addition of biogas slurry suspension can shorten the time for the reactor to reach the high temperature period.Compared with CK（without biochar addition）,the peak temperature of the reactor increases by 4.9°C（T1）,and the duration of the high temperature period increases by 3-4d.The addition of biogas slurry suspension decreased the conductivity（EC）of the compost,and the EC decreased by3.1%-6.2%compared with CK at the end of composting.GI also improved,among which T2 was the highest（107%）.