Study On The Performance Of The Co-digestion Of Rice Straw And Excess Sludge

With the substantial increase in the output of urban surplus sludge and rice straw,its harmless and efficient resource treatment and disposal have attracted much attention.Anaerobic digestion technology,as a technology for the reduction and recycling of organic solid waste that has attracted international attention,can not only realize the stabilization of organic solid waste,but also generate clean energy（Biogas）.Therefore,in order to solve the problems of low single digestion efficiency of surplus sludge and insufficient utilization of rice straw as a resource,this study selected three main varieties of indica rice,japonica rice and glutinous rice to carry out joint anaerobic digestion batch experiments with surplus sludge.Add in the ratio of organic matter VS _{inoculated sludge}:VS _{rice straw}=1:1.5,to explore the effects of different varieties of rice straw on the stability of anaerobic digestion of excess sludge,biogas production performance,and changes in microbial community structure.Based on the selection of the best varieties of rice straw,a semi-continuous combined anaerobic digestion experiment was carried out to analyze the stability of the digestive system,the performance of biogas production,the performance of sludge dehydration and the nutrient composition,with a view to constructing efficient and stable anaerobic co-digestion system of rice straw and sludge.Research shows:（1）The addition of different varieties of rice straw has a significant impact on the p H value and volatile fatty acid content（VFAs）of the sludge anaerobic digestion system.Among them,the anaerobic co-digestion of glutinous rice straw and sludge experiment group（S3）has better hydrolysis performance,and it has the most obvious effect on promoting methane production in the sludge anaerobic digestion system.The average methane content is determined by the sludge single digestion experiment group（CK）40.74%to 56.29%（S3）,the cumulative biogas production is 543.16m L/g VS,and the cumulative methane production is 305.75 m L/g VS..（2）The addition of different varieties of rice straw significantly affects the diversity of microbial communities in the sludge digestion system.In each experimental group,Bacteroidetes,Actinobacteria,Proteobacteria,Methanosarcina,Methanosaeta and Candidatus＿Nitrocosmicus changed significantly,and the relative abundance of each dominant bacterial group during the digestion process kept the same.At the same time,in the anaerobic digestion system,VFAs are negatively related to most bacteria and archaea.When VFAs are too high or too low,they will affect the growth of microorganisms in the system.Therefore,controlling VFAs in a certain range is an important factor to maintain the growth and reproduction of microorganisms in the anaerobic digestion system.（3）In the semi-continuous experiment of combined anaerobic digestion of glutinous rice straw and sludge,the average daily gas production after adding glutinous rice straw increased from 757.825 m L/d in the sludge single digestion experiment group（A）to 3052.25 m L/d（B）,an increase of 302.76%,φ（CH₄）increased from 38.6%（A）to 53.7%（B）.The addition of glutinous rice straw has a greater impact on the dehydration performance of the digestive juice.On the 38th day,the polysaccharide content increased to 22.34 mg/g,and the CST time reached 308.4s,which greatly reduced the dehydration performance of the sludge,which was not conducive to Subsequent dehydration treatment of digestive juice.（4）Biogas slurry and biogas residue contain a large amount of nitrogen（N）and phosphorus（P）nutrient elements.The addition of glutinous rice straw increases the content of total nitrogen（TN）and total phosphorus（TP）in biogas slurry and biogas residue.The N element mainly remained in the biogas residue.The TN content of the biogas residue in the experimental group with glutinous rice straw increased to4200～7700 mg/kg.P element mainly remained in the biogas slurry,and the TP content of the biogas slurry in the experimental group added with glutinous rice straw increased to 21.11～34.17 mg/L.