Microbial community structures in an integrated two-phase anaerobic bioreactor fed by fruit vegetable wastes and wheat straw

The microbial community structures in an integrated two-phase anaerobic reactor（ITPAR）were investigated by 16 S r DNA clone library technology. The 75 L reactor was designed with a 25 L rotating acidogenic unit at the top and a 50 L conventional upflow methanogenic unit at the bottom, with a recirculation connected to the two units. The reactor had been operated for 21 stages to co-digest fruit/vegetable wastes and wheat straw, which showed a very good biogas production and decomposition of cellulosic materials. The results showed that many kinds of cellulose and glycan decomposition bacteria related with Bacteroidales,Clostridiales and Syntrophobacterales were dominated in the reactor, with more bacteria community diversities in the acidogenic unit. The methanogens were mostly related with Methanosaeta, Methanosarcina, Methanoculleus, Methanospirillum and Methanobacterium; the predominating genus Methanosaeta, accounting for 40.5%, 54.2%, 73.6% and 78.7% in four samples from top to bottom, indicated a major methanogenesis pathway by acetoclastic methanogenesis in the methanogenic unit. The beta diversity indexes illustrated a more similar distribution of bacterial communities than that of methanogens between acidogenic unit and methanogenic unit. The differentiation of methanogenic community composition in two phases, as well as pH values and volatile fatty acid（VFA） concentrations confirmed the phase separation of the ITPAR. Overall, the results of this study demonstrated that the special designing of ITPAR maintained a sufficient number of methanogens, more diverse communities and stronger syntrophic associations among microorganisms, which made two phase anaerobic digestion of cellulosic materials more efficient.

高含固率秸秆和牛粪混合物料发酵产甲烷工艺

该研究针对高含固率纤维质物料难以连续厌氧发酵、甲烷产率低的问题，利用所研制的一套能连续进出料、具有高有机负荷承载力的新型反应器，以玉米秸秆和牛粪为原料，通过调控搅拌强度和投料强度在反应器内建立了“分区发酵”体系，比较了3种高含固率（10%、15%和20%）物料在不同有机负荷下的甲烷容积产率，系统研究了物料含固率、搅拌强度和投料强度对“分区发酵”体系形成功能分区的高度、各功能区的pH值和甲烷容积产率的影响，旨在为纤维质物料产甲烷提供高效的发酵工艺和可靠的运行参数。结果表明，含固率为10%和15%的反应器，甲烷容积产率随有机负荷的增加而增加，平均甲烷体积分数稳定在52%左右，二者在有机负荷分别为13.44和20.17 kg/（m3·d）时，甲烷容积产率最高，分别为1.62和1.66 m3/（m3·d），在有机负荷分别为20.17和30.0 kg/（m3·d）时，甲烷产量明显下降；含固率为20%的反应器，甲烷容积产率随有机负荷的增加基本保持不变且较低（0.98 m3/（m3·d）），当有机负荷达到30.0 kg/（m3·d）时，发酵体系酸败，甲烷产量明显下降。双因素优化结果表明，当物料含固率为10%和15%、搅拌强度为6～12 h/d、投料强度为6.5～10 d时，发酵体系可形成高效的酸化区和产甲烷区，二者的高度之比为1.1～1.6：1，甲烷容积产率可达1.63～1.69 m3/（m3·d）。综上，该反应器可实现含固率为10%～20%的纤维质物料连续进出料，并在含固率为10%和15%时能高效、稳定地产甲烷，通过调控搅拌强度和进料强度能提高其甲烷容积产率。该发酵工艺有规模化应用的前景。