Abstract: In order to clarify the influence of biogas slurry reflux on anaerobic fermentation performance，experiments with different reflux ratios，0（control），25%，50%，75%，100% were carried out under the condition of mesophilic temperature（35℃）with chicken manure and corn stover as co⁃digestion materials by semi⁃continuous anaerobic fermentation.Parameters such as gas production，physical and chemical properties of the slurry and chemical oxygen demand（COD）removal rate were analyzed to establish the optimum biogas slurry reflux ratio of anaerobic co⁃digestion of chicken manure and corn stover.The results showed that the maximum total methane production 96.87 L，6.56% higher than that of the control（90.90 L）and the highest COD average removal rate 62.40%，2.18 percentages points higher than that of the control（60.22%）were obtained at the reflux ratio of 25%. The changes of pH，VFA，ammonia nitrogen and COD in the fermentation system were steady and the ratio of volatile fatty acids to total alkalinity（VFA/TA）less than 0.3 indicated the stability of the fermentation system.VFA，ammonia nitrogen and COD increased，the total methane production and COD degradation rate gradually decreased with the increase of reflux ratio when the reflux ratio was greater than 25%.When the reflux ratios were increased to 75%，100%，VFA and ammonia nitrogen increased rapidly with the extension of fermentation time，showing accumulation in the fermentation system，and the average contents of free ammonia（FAN）were 303.14，522.15 mg/L，respectively，which greatly exceeded the limit of FAN inhibition（200 mg/L）.When the reflux ratios were 50%，75%，100%，the total methane productions were 87.08，79.31，69.66 L，respectively，which were 4.20%，12.76%，23.37% lower than the control，and the COD average removal rates were 48.46%，37.85%，29.56%，respectively，which were 11.76，22.37，30.66 percentage points lower than that of the control group.The VFA/TA less than 0.3 indicated the stability of the fermentation system when the reflux ratio was 50%，and the VFA/TA more than 0.3 indicated the instability of the fermentation system when the reflux ratios were 75%，100%.In conclusion，the optimal reflux ratio is 25%.Excessive slurry reflux ratio enhances the accumulation of VFA andammonia nitrogen and inhibits the gas production in the anaerobic fermentation system.

Key words: Biogas slurry, Reflux ratio, Chicken manure, Corn stover, Anaerobic co?digestion, Fermentation performance

摘要： 为明确沼液回流对厌氧发酵特性的影响，以鸡粪和玉米秸秆为混合发酵原料，设置0（对照）、25%、50%、75%、100% 5个不同回流比，在中温（35 ℃）条件下进行半连续式厌氧发酵试验，通过测定和分析产气指标、发酵料液的理化性质及化学需氧量（COD）去除率，确立鸡粪和玉米秸秆混合厌氧发酵适宜的回流比。结果表明，回流比为25%时，系统产气效果最好，甲烷总产量为96.87 L，较对照（90.90 L）提高6.56%；COD平均去除率最高，为62.40%，较对照（60.22%）提高2.18个百分点；此时，发酵系统的pH值及挥发性脂肪酸（VFA）、氨氮、COD质量浓度等均较稳定，发酵系统处于稳定状态（VFA/TA<0.3）。当回流比>25%时，VFA、氨氮、COD质量浓度等开始随回流比的提升而增加，甲烷总产量和COD去除率则随回流比的提升而逐渐降低。回流比提升至75%、100%时，VFA、氨氮质量浓度在其发酵周期内随发酵时间的延长而快速增长，出现明显累积，此时游离氨（FAN）平均质量浓度分别为303.14、522.15 mg/L，大大超过了FAN的抑制限值（200 mg/L）。回流比为50%、75%、100%时，甲烷总产量分别为87.08、79.31、69.66 L，较对照分别降低4.20%、12.76%、23.37%；COD平均去除率分别为48.46%、37.85%、29.56%，较对照分别降低11.76、22.37、30.66个百分点。回流比为50%时，VFA/TA<0.3，发酵系统处于稳定状态；回流比为75%、100%时，VFA/TA>0.3，发酵系统不稳定。综上，鸡粪和玉米秸秆混合厌氧发酵适宜的回流比为25%，回流比过高时会引发厌氧发酵系统VFA和氨氮的累积，抑制产气。

关键词: 沼液, 回流比, 鸡粪, 玉米秸秆, 混合厌氧发酵, 发酵性能