Research On Co-digestion Treatment Of Food Waste And Excess Sludge In Anaerobic Membrane Bioreactor

With the improvement of the people's quality of life and the level of urbanization,the food waste and waste activated sludge generated in China every year are gradually increasing.Co-fermentation technology is considered to be the best way to deal with food waste and waste activated sludge,which can effectively alleviate the problems of single substrate fermentation.The treatment efficiency and stability of conventional anaerobic fermentation systems are insufficient,which will affect the co-fermentation process,and the high-efficiency interception of the membrane components of the anaerobic membrane bioreactor?AnMBR?realizes the effective separation of SRT and HRT,and improves the sludge.The effect of concentration,system stability and anaerobic fermentation efficiency.Therefore,in this study,through co-fermentation continuous experiments,active batch experiments,membrane resistance experiments,and high-throughput sequencing,we analyzed the co-digestion of anaerobic membrane bio-fermentation systems for food waste?self-provisioned?and waste activated sludge under different load conditions The impact of the efficiency,stability and kinetic characteristics of the system explored the microbial community changes at different stages and their correlations,and obtained the following main conclusions:?1?The organic load for the stable operation of the anaerobic membrane bioreactor gradually increased from 3.2gCOD/L/d to 12.9gCOD/L/d,and the corresponding HRT was gradually shortened from 30 days to 7.5 days.The methane content has been maintained above 60%,and the pH value in the system is 7.5?7.8,which is in a suitable range.The membrane module was replaced 4 times during the operation process.With the increase of organic load,the value of dTMP/dt is from 0.70kPa/d increased to 2.36kPa/d afterwards,?2?the membrane pollution speed was accelerated,and the cake layer pollution was the main cause.When the organic load is 9.7gCOD/L/d,a certain amount of volatile fatty acids?VFAs?accumulate in the system,the concentration is 0.454gCOD/L,mainly acetic acid;when the organic load is12.92COD/L/d,The concentration of VFAs in the system increased to 2.09gCOD/L,mainly propionic acid.When the organic load was increased to 19.4gCOD/L/d?the corresponding HRT was 5 days?,the pH value in the system dropped to 3.22 within a few days,the VFAs concentration was as high as 6.1gCOD/L,and the reaction system collapsed.?2?During the stable operation of the anaerobic membrane bioreactor,the degradability of organic matter has been in good condition,the removal rate of COD,polysaccharides and proteins has been maintained above 90%,the methane production rate has been maintained at 0.21?0.27LCH₄/gCOD.The yield is maximized when the organic load is 6.5gCOD/L/d,at which time the system has the best methanogenic efficiency and the highest COD utilization.?3?As the organic load increases from 3.2gCOD/L/d to 12.9gCOD/L/d,the specific methanogenic activity of the anaerobic membrane bioreactor with acetic acid as the substrate is from 0.14gCH₄-COD/VSS/d Increased to 0.924gCH4-COD/VSS/d,and the experimental results showed that the specific methanogenic activity with acetic acid as the substrate all reached the maximum at the concentration of 8gCOD/L.The specific methanogenic activity with propionic acid as the substrate achieves the maximum when the organic load is 9.7gCOD/L/d,the specific methanogenic activity is 0.588gCH4-COD/VSS/d,and the organic load is 12.9gCOD/L/d The specific methanogenic activity with propionic acid as a substrate showed a downward trend.At this time,a large amount of VFAs mainly propionic acid accumulated in the system.?4?At the bacterial level,Firmicutes,Bacteroidetes,Chloroflexi,and Proteobacteria account for the main part of the entire bacterial community and are anaerobic membrane organisms.Dominant bacteria in the bacterial community at all stages of the reactor.At the archaeological level,Methanosarcina is the dominant genus of mixed nutrients at various stages in the reactor.According to redundancy analysis,the specific methanogenic activity of Methanosarcina and propionic acid as substrate is positively correlated?r=0.74?,Which has a significant positive correlation with alkalinity?r=0.85,p<0.05?,indicating that the ability of this system to handle propionic acid is related to the enrichment and growth of Methanosarcina.Increasing the relative abundance of Methanosarcina in the system may improve the system to a certain extent The degradation ability of propionic acid,in addition,the high alkalinity value of the operation process of this system may be one of the reasons why Methanosarcina has become the dominant genus.Another hydrogen-trophic Methanobacterium with obvious change trend during operation was found to have a significant positive correlation with HRT?r=0.960,p<0.01?,pH?r=0.959,p<0.01?through the redundant analysis,indicating It is suitable for growth in a higher pH environment,and a shorter HRT will adversely affect its enrichment growth.