Study On A Dynamic Membrane Anaerobic System Of Co-digestion With Food Waste And Cow Manure At High Load Rate

Anaerobic Dynamic Membrane Bioreactor（DMBR）has been widely used for its advantages of good solid-liquid separation and low cost.However,the existing research mainly focuses on wastewater treatment,and the application of solid waste treatment is less.In this study,a self-made DMBR was used to start anaerobic co-digestion methane production system,before which a bitch test of optimization has been carried out,for efficient treatment of food waste（FW）and cow manure（CM）to explore the effect on methane production by An DMBR.After stable operation under high load,the change of feedstock mixing ratios（FW/CM）and substrate to inoculum ratio（S/I）on the performance of sludge after long-term acclimatization was explored compared to unacclimted sludge.The effects of biological enzymes and microbial community structure during the stable operation of DMBR were further explored to the reason that stability of the long-term operation.At the same time,the difference between the continuous stirred tank reactor（CSTR）and DMBR under the same organic load（7.1±0.5 g VS/L/day）has explored.The conclusions reached are as follows:（1）FW/CM and S/I will significantly affect the efficiency of four anaerobic fermentation steps（hydrolysis,acid production,acetic acid production,and methane production rate）and kinetic parameters in the single or co-digestion of FW and CM.Under the condition（FW/CM=2.5 g VS/g VS,the S/I ratio≤0.56 g VS/g VS）,the mesophilic anaerobic co-digestion bioreactor can be successfully started and run stably,which further confirms the above optimal conditions.It can be provide scientific basis for energy recovery of co-digestion of FW and CM.（2）During the semi-continuous DMBR operation,stable and high-rate anaerobic digestion can be achieved through the co-digestion of CM and FW.At an organic load rate（OLR）of 11.9 g COD/L/day,the methane yield and methane production were 250m L/g COD and 2.71 L CH₄/L/day.At the same time,the degradation rates of cellulose,hemicellulose and lignin are 78.3%,58.8%and 47.5%,respectively,which is consistent with the analysis of FTIR.The content of coenzyme F₄₂₀ and the level of lignocellulolytic enzymes,the co-digestion of FW and CM can increase the anaerobic rates of hydrolysis and methanogenesis in DMBR.The co-digestion system of CM and FW can run stably for a long time,which has good elasticity of inhibition,and it also helps the work of enzymes and microorganisms to improve the performance of methanogenesis.（3）The optimal FW/CM ratio of unacclimated sludge is 2.5 g VS/g VS,and the optimal S/I ratio is not higher than 0.56g VS/g VS.After starting the AD system,gradually increase the OLR.The sludge has been acclimated for a long time,the optimal FW/CM ratio has been optimized to 3.5 g VS/g VS,and the optimal S/I is not higher than 0.79 g VS/g VS.Through high-throughput sequencing analysis,it can be clarified that the long-term acclimatization of the reactor sludge can increase the abundance and diversity of bacteria,archaea and fungi in DMBR.Moreover,the microbial structure changes significantly,and the AD and cellulose degrading enzymes secreted by the increasing microbes,which promotes the hydrolysis rate of the system.On the other hand,the increasement in the abundance of hydrogen trophic methanogens（such as Methanoculleus）with high tolerance to ammonium makes the system more stable and has a higher impact load resistance and capacity effect.（4）In high OLR operation,both DMBR and CSTR can operate at the same organic loading（7.1±0.5 g VS/L/day）,and its both show a good operating performance,which indicated that domesticated sludge is stronger for different reactor configurations.DMBR showed better performance,CH₄ yield reached 250±31 m L CH₄/g COD higher than CH₄ yield of CSTR（218±23 m L CH4/g COD）,and DMBR had longer SRT and higher secretion of the content of AD enzyme and cellulase enzyme that keep the efficient and stable operation of the reactor.