A Comparative Study Of Three Bioreactor Systems For Food Waste On Anaerobic Digestion Performance And Microbial Community

The content of easily degraded organic matter in food waste is high,If used for anaerobic digestion to produce methane,it can both reduce pollution and recycle energy.At present,the mainstream anaerobic digestion technology in China is wet anaerobic digestion,because it is easy to manage.Meanwhile,the technology also has many disadvantages,such as high costs,low processing capacity and high energy consumption.In Europe,most organic waste is treated by dry anaerobic digestion process.Take Dranco as an example,the advantages of this process mainly include: saving space and costs,no scum and sediment,saving energy and so on.Therefore,dry plug flow system was simulated and compared with wet continuous stirring tank reactor and dry continuous stirring tank reactor under the same condition to observe the similarities and differences between them on methane-producing performance and microbial communities,and select out the reactor with the best methane-producing performance.During the whole experiment,the wet continunous stirring tank reactor,the dry plug flow reactor and the dry continunous stirring tank reactor operate stably under an organic load of 3kgVS·L-1·d-1,during which the methan-producing rate,pH,volatile fatty acids,alkalinity,ammonia nitrogen are measured.After stable operation for a period of time,the fermentation liquor in three reactors are sampled and sequenced.The measured results indicate that the methane yield,ammonia nitrogen,volatile fatty acids,alkalinity and pH of the wet continuous strring tank reactor are 0.55L/gVS,654mg/L,128 mg /L,3545 mg /L,7.21,which is 0.48/gVS,565 mg /L,403 mg /L,5377 mg /L and 7.46 in the dry plug flow reactor,and 0.50L/gVS,3014 mg/L,962 mg/L,11319 mg/L and 7.49 in the dry continuous strring tank reactor.Sequencing results show that the dominant bacterium genuses in the wet continuous strring tank reactor are ST-12K33 norank,Anaerolineaceae norank,Actinobacteria unclassified,and Ruminococcaceae unclassified.The dominant archaean genuses in the wet continuous stirring tank reactor are methanosaeta,methanobacterium and methanospirillum.In the dry plug flow reactor.,Anaerolineaceae norank,Christensenellaceae_R-7_group and Georgenia are dominant bacterium genuses.,and methanosaeta is the dominant archaean genu.Christensenellaceae_R-7_group,WS6 norank,Fastidiosipila,vadinBC27_wastewater-sludge_group are dominant bacterium genuses and methanosacrina and methanosaeta are the dominant archaean genuses in the dry continuous strring tank reactor.The main conclusions are as follows: 1)under the load of 3kgVS·L-1·d-1,the wet continuous strring tank reactor has the best methane-producing performance.Compared with the two dry reactors,its concentration of ammonia nitrogen,VFA and alkalinity are much lower that it is less likely to inhibit the system and corrode the reactor.2)there are more species of archaea and bacteria in the dry system than the wet one,and the microbial communities between them are quite different.3)systems with higher concentration of volatile fatty acids have larger abundance of firmicutes.4)Of all the three reactors,the dry plug flow reactor has the highest relative abundance of family Anaerolineaceae,indicating that the solid content,stirring and ammonia concentration had a certain influence on its growth.5)Three reactors are dominated by acetotrophic methanogens,but the inhibition of ammonia nitrogen on methanosaeta causes the dominant bacteria to change from methanosaeta to methanosacrina,and the relative abundance of hydrotrophic methanogen in the wet reactor is higher than that in the dry reactor.