Enrichment Of Methanogenic Butyrate-degrading Microbial Consortia And Bioaugmentation To Acidified ASBR

In this study,two types of methanogenic butyrate-degrading microbial consortia(hydrogen-producing acetogens and formate-producing acetogens be the dominant microbes respectively)were enriched and dosed into the acidified ASBR.The effect of bioaugmentation with enriched microbial consortia on the recovery of acidifi-cation was investigated.Furthermore,the succession of microbial community in a bioreactor was studied.The main conclusions are as follows:Microbial consortia B-H(hydrogen-producing acetogens as the dominant microbes)and microbial consortia B-F(formate-producing acetogens as the dominant microbes)were enriched successfully.The specific methanogenic activity for formate,acetate,propionate and butyrate of microbial consortia B-H and B-F were 0.441,2.546,1.125,3.110 gCOD/gVSS d and 1.540,2.031,1.137,2.855 gCOD/gVSS d respectively.The dominant microbial groups were Syntrophomonas(18.84±1.68%%),Methanosaeta spp..(22.81±0.68%),Methanobacteriales(26.28±1.75%)and Methanomicrobiales(6.03±0.23%)in consortia B-H and Syntro-phomonas(14.13±0.46%),Methanosaeta spp.(18.24±0.32%),Methanobacteriales(20.97±1.37%)and Hethanomicrobiales(9.02±0.47%)in consortia B-F.And it was speculated that Methanomicrobiales played a major role in the metabolism of formic acid to methane.Three anaerobic sequencing batch reactors(R1,R2,R3)were subjected to a double transient organic shock loads in which the influent glucose concentration was increased from 4000mgCOD/L to 8000mgCOD/L.After the shock loads,the COD removal efficiencies decreased to 43.9%,44.9%,43.9%and effluent pH were 5.3,5.4,5.12 respectively.And Smithella,Methanosarcina spp.,Methanosaeta spp.and Meth-anobacteries were inhibited by the accumulation of VFA and low pH.Among them,Smithella was the most severely inhibited in three reactors,the relative abundance of which decreased dramatically from 7.97±0.53%,7.56±1.35%,9.29±0.84%to 1.34±0.06%,2.98±0.56%,3.7±0.4%while the relative abundance of Syntrophomonas increased slightly.The results indicated that the propionate metabolic pathway of glucose was severely inhibited,which led to the accumulation of VFA.Dosing microbial consortia B-H and B-F(dosage:10%of total MLVSS in reactor)can successfully promote the recovery of acidification.The recovery time of non-bioaugmented R1 reactor,B-H bioaugmented R2 reactor and B-F bioaugmented R3 reactor were 110 days,40 days and 85 days,respectively.Moreover,bioaug-mentation of B-H and B-F enhanced the metabolic steps of methane production from hydrogen and acetic acid effectively by increasing the relative abundance of Methanosarcina spp.,Methanosaela spp.and Methanobacteriales,which contributed to the rapid recovery of Smithella because of the decrease of hydrogen and acetic acid.Due to the rapid recovery of Smithella,the acidified R2 and R3 reactors recovered more quickly than non-bioaugmented reactor.Furthermore,microbial consortia B-H showed better bioaugmentation effect than that of consortia B-F.The main reason was that the higher relative abundance of Methanobacteriales in microbial consortia B-H signigicantly enhanced the metabolism of hydrogen to methane and further promoted the recovery of Smithella.