pH值调控对秸秆两阶段厌氧发酵产沼气的影响

摘要

两阶段厌氧发酵产沼气是秸秆沼气化利用的重要方式之一。秸秆厌氧发酵过程包括水解产酸和产甲烷两个阶段，水解产酸是秸秆沼气化的限速步骤，也是目前的研究重点。pH值是影响物料水解产酸的重要因素，目前的研究多集中于酸性环境对物料水解产酸的影响，碱性环境对物料水解产酸的影响还未见研究报道。在实验室条件下，每天调节水解产酸反应器发酵液pH值至8.0（T1）、9.5（T2）和11.0（T3），CK在实验过程中不调节水解产酸反应器发酵液pH值，水解产酸反应器排出的水解酸化液直接用蠕动泵泵入产甲烷反应器内产甲烷，分析了发酵过程中水解产酸反应器日产气量、甲烷含量、水解酸化液 pH 值、COD 浓度以及产甲烷反应器产气特性的变化。结果表明：在不调节水解产酸反应器水解酸化液pH值条件下，秸秆两阶段厌氧发酵可以正常进行，秸秆干物质（TS）产气量为281.28 mL·g-1，平均甲烷含量为47.36%；T1水解产酸反应器内水解酸化液pH值稳定在7左右，系统累积产气量、总产甲烷量和平均甲烷含量分别较CK大幅增加了24.51%、29.39%和2.5个百分点；T2和T3水解产酸反应器产气明显受到抑制，水解酸化液后续产甲烷亦受到明显抑制，产甲烷反应器累积产气量分别仅为CK的89.97%和17.48%，总产气量仅为T1的67.67%和10.20%；维持水解产酸反应器至碱性条件促进了秸秆中半纤维素的溶出和木质素的破坏，但不利于纤维素的溶出，TS损失率的结果与产气的结果一致。综合以上结果，调节水解产酸反应器水解酸化液pH值至8.0对提高秸秆两阶段厌氧发酵产沼气有明显的促进作用。%Two-stage anaerobic digestion of agricultural straw is an important way for biogas production in China. The anaerobic digestion process was divided into two stage, hydrolysis and acidification, and methanogenesis. Large literature search showed that hydrolysis and acidification is the limiting step of biogas production of biosolid wastes. How to improve the hydrolysis and acidification rate of biosolid wastes? Much work has been done, including pretreatment, co-digestion, high efficient microbial inoculants, fermentation process control, et al. PH value is an important factor to hydrolysis and acidification of biosolid wastes. Much work has been done on characteristics of hydrolysis and acidification of biosolid wastes in acidic environment, but there was little information on characteristics of hydrolysis and acidification of biosolid wastes in alkaline environment. In order to evaluate the effect of alkaline environment control on hydrolysis and acidification and subsequent biogas production of agricultural straw, changes of daily biogas yield, methane content, pH value, COD content of hydrolysis and acidogenic phase and characteristics of biogas production of methanogenic phase were studied. The results showed that two-phase anaerobic fermentation of agricultural straw could be operated normally and TS biogas yield and average methane content were 281.28mL/g TSadded and 47.36%, respectively. Cumulative biogas yield of hydrolysis and acidogenic phase, average methane content and cumulative methane yield of treatment of adjusting pH value of hydrolysate to 8.0 daily was improved by 24.51%. 2.5 percent and 29.39%. Adjusting pH value of hydrolysate to 9.5 and 11.0 daily could inhibit biogas production of hydrolysis and acidogenic phase and increase COD content of hydrolysate, but it was bad for biogas production of hydrolysate and cumulative biogas yield of methanogenic phase were only 89.97% and 17.48% to that of CK. Maintaining hydrolysis and acidogenic phase in alkaline environment was beneficial for dissolving out of hemicellulose and lignin but bad to cellulose.