Investigation On Anaerobic Digestion Performance Of Batch Experiment And Sequencing Experiment For Ammonia-Potassium Compound Modification Rice Straw

The lignin contained in rice straw hinders the accessibility of cellulose and hemicellulose to microorganisms,and restricts the progress of anaerobic digestion.At present,a single modifying reagent cannot meet the demand for destroying complex lignocellulose structures.At the same time,the complete mixing setup of the single-stage CSTR leads to the phenomenon of"short-circuit" of the material,The materials in effluent are not completely degraded,resulting in the loss of material and microorganism,which limits the anaerobic digestion potential.Therefore,in this study,the method of composite modification of rice straw with KOH and ammonia was designed to more effectively disrupt the crystal structure of cellulose,increase the accessibility of cellulose,hemicellulose,and anaerobic microorganisms,and further increase anaerobic digestion production,to improve the nutritional value and economic value of biogas residue biogas slurry.Two-stage anaerobic digestion system was adopted to solve the "short-circuit" problem of the CSTR reactor and improve the anaerobic digestion efficiency.Firstly,different concentrations of ammonia-potassium hydroxide were investigated on the anaerobic digestion performance of rice straw.The results showed that the modification effect was improved at 1%KOH-1%NH3.The highest daily biogas production was achieved(1350 mL)and the cumulative methane production was 9824.3 mL,which increased by 35.0%and 15.3%respectively compared with the untreated group.The biogas yield,TS reduction rate and VS reduction rate were 16.0%,14.2%and 21.8%higher than that of control,respectively.Secondly,the effect of 1%KOH-1%NH3 combined modification on the anaerobic digestion performance of single CSTR was studied.The results showed that the methane yield and TS reduction rate of pretreated group(R1)were 4.5%-5.9%and 48.4%-55.4%higher than the control(R0),also Ri showed better system buffering capability.The system stability with 90 gTS·L-1 organic loading rate fluctuated significantly,while stable state could be recovered more quickly than the control.Thirdly,HRT36+12d and HRT24+24d serial anaerobic digestion system were operated and compared to the conventional single CSTR at the same HRT of 48 d.The result showed that the anaerobic digestion process was mainly carried out in first-stage reactor.The VS removal rate of HRT24+24d first-stage and HRT36+12d first-stage were accounted for 85.1%-97.2%and 87.5%-97.3%of the total VS removal rate,respectively.The methane yield of HRT36+12d was 4.01%-4.05%,10.4%-13.3%and 16.9%-19.5%higher than that of HRT24+24d,the modification single system(Ri)and no modification single system(R0),respectively.At the same time,HRT36+12d showed better system stability than HRT24+24d.The stability of two system at 85 gTS· L-1 fluctuated significantly,while HRT24+24d system fluctuated earlier and had a longer recovery time.These was mainly because the HRT24+24d first-stage reactor had a larger daily feeding volume than HRT36+12d,which had a greater impact on the anaerobic system.The first order kinetics model and R-X graphical methods of all systems were used to simulate the hydrolysis rate,and the result showed that the two-stage system was better than the single.Finally,microbial diversity and community structure of single system and two-stage system(HRT36+12d)were analysis by high-throughput sequencing.The first-stage system of two-stage could increase the bacterial abundance,while the second-stage could significantly increase the bacterial diversity,which was different from the single-stage system bacterial flora.In the distribution of archaea,Euryarchaeota was the dominant phylum,accounting for 51.2%,70.2%and 36.2%of the total archaea in HRT36+12-?,HRT36+12-? and R1,respectively.