沼液回流对秸秆与污泥混合中温厌氧消化的影响

为了提高秸秆与市政污泥混合厌氧消化的消化产率，以秸秆污泥混合物作为底物，在批次实验中研究不同沼液回流对中温（35 ℃）混合厌氧消化过程的影响。实验采用0% 、20%、30%、40%、50%和60%等6种不同的沼液回流量，分析不同沼液回流量下产气量、甲烷含量、发酵过程氨氮含量、sCOD、总挥发酸（VFAs）的变化情况。结果表明：50%的沼液回流产气量和甲烷产量均最大，分别是1 645 mL和797.5 mL，TS和VS去除率达到17.5%和47.8%，单位VS甲烷产量为613.45 mL·g-1，较未加沼液的发酵瓶提高了37.7%，且无VFAs积累。过高的沼液回流量提升了厌氧反应的氨氮浓度，对厌氧产气过程产生了抑制。50%沼液回流量可以作为秸秆污泥混合厌氧消化最佳回流量。

Effect of slurry recirculation on mesophilic anaerobic digestion of straw and sludge

In order to improve the digestibility of anaerobic co-digestion of straw and municipal sludge, the effects of slurry recirculation on the anaerobic co-digestion process at medium temperature (35 ℃) were studied in batch experiments with the mixture of straw and sludge as the substrate. The recirculation ratio of 0%, 20%, 30%, 40%, 50% and 60%, were adopted and the change of gas yield, methane content, ammonia nitrogen content, sCOD and total volatile acid (VFAs) were analyzed in the fermentation process. The results showed that the maximum gas and methane production (1 645 mL for gas production and 797.5 mL for methane production) were obtained at a recirculation ratio of 50% with a TS removal efficiency of 17.5% and a VS removal efficiency of 47.8%. The methane production rate was up to 613.45 mL·g-1, which was 37.7% higher than that without slurry recirculation, and there was no VFAs accumulation. Excessive slurry recirculation enhances the concentration of ammonia nitrogen in anaerobic reaction and inhibits anaerobic gas production process, therefore, the recirculation ratio of 50% can be used as the optimal ratio in anaerobic digestion of straw and sludge.