| Biological hydrogen production method anaerobic fermentation due to short reaction cycle,simple operating conditions,low cost has been widely studied,in order to effectively improve the efficiency of anaerobic fermentation hydrogen production,researchers have carried out the addition of biochar,metal ions,and some trace elements as fillers or efficient additives research.In this experiment,corn stover biochar and activated sludge were used to carry out anaerobic hydrogen production fermentation,and the effects of appropriate biochar addition on the hydrogen production performance of activated sludge anaerobic fermentation and community structure microbial diversity in activated sludge were explored.In this experiment,Hungate roller tube and anaerobic culture technology were used to screen high-efficiency hydrogen-producing bacteria from activated sludge samples,compare and analyze the effects of biochar addition on gas production and hydrogen production of hydrogen-producing bacteria,and determine the optimal amount of biochar.The effects of the addition of appropriate amount of biochar and the control of influent COD concentration and hydraulic residence time HRT on the operation of the reactor were comprehensively analyzed,and the COD removal rate,p H value,redox potential ORP,effluent suspended solids TS,activated sludge suspended solids mass concentration MLSS,volatile suspended solids mass concentration MLVSS were comprehensively analyzed during reactor operation.Changes in liquid phase fermentation products and glucose utilization.The changes of microbial community structure in activated sludge in the reactor were analyzed by high-throughput sequencing technology,the influence of environmental factors on microbial community composition was analyzed,and the function of microbial community was predicted.A high-efficiency hydrogen-producing bacterium was screened from activated sludge,named G-42,with a cumulative gas production of 2970 m L·L-1 culture and a cumulative hydrogen production of 903.4 m L·L-1 culture after 36 h culture,which was identified as Clostridium beijerinckii.Set the biochar addition amount to 0,5,10,15g·L-1,the hydrogen-producing bacteria G-42 were cultured by static experiments,and the results showed that when the amount of biochar was 10 g·L-1,the highest gas production per unit volume and hydrogen production were obtained,and the cumulative gas production was 3960 m L·L-1 culture,which increased by 33.3%compared with the addition of biochar hydrogen producing bacteria,and the cumulative hydrogen production was 998.4 m L·L-1 culture,which increased by 10.5%compared with the addition of biochar hydrogen producing bacteria.After 72 h aeration pretreatment,the sludge settlement performance of activated sludge improved and appeared flocculent.Combine activated sludge with 10 g·L-1 corn stover biochar is added to the CSTR reactor,which starts operation at low load.The results showed that when the COD concentration of the influent water was 4000 mg·L-1,HRT is 12 h,the reactor runs the highest gas production and hydrogen production,the average daily gas output reaches 42.9 L·d-1,the average daily hydrogen output reaches 16.1 L·d-1,the average hydrogen content in the gas reaches about 38.8%,and the highest hydrogen content reaches 56.3%.The p H value was stable at 4.3～4.4,and the total mass concentration of the liquid phase fermentation product was 1319 mg·L-1,the reaction fermentation broth was mainly acetic acid,butyric acid and ethanol,and the mass concentration of ethanol reached 320 mg·L-1.The sum of the mass concentrations and ethanol and acetic acid was 810 mg·L-1,accounting for 61.4%of the total mass concentration,the fermentation type is ethanol and butyric acid mixed fermentation.The activated sludge inoculated into the reactor is abundant in unclassified Anaerolineaceae,Thiobacillus,Polaromonas,unclassified Betaproteobacteria,and Ornatilinea at the genus level.The rich flora in the reactor ensures the microbial diversity of the inoculated sludge.Biochar and activated sludge were added to the reactor to start operation,and at the beginning of the first stage of reactor operation,the microbial community in the activated sludge changed significantly,including Prevotella,Clostridium sensu stricto,and unclassified Lachnospiraceae.When the reactor was run to the middle and late stages of the first stage and the second stage,the dominant flora in the activated sludge changed to Ethanoligenens,Prevotella and Enterobacter,and ethanol bacillus in the reactor became the dominant flora,with a community abundance of up to 49.4%.The addition of a specific amount of biochar and the control of COD concentration and hydraulic residence time HRT in the reactor influent water increased the number of hydrogen-producing bacteria participating in ethanol-type fermentation with the progress of the anaerobic fermentation reaction,which was conducive to the anaerobic fermentation in the reactor. |
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