进料浓度对鸡粪长期高温甲烷发酵的影响

通过固定水力停留时间（HRT）为20d，逐步提高进料总固体（TS）浓度为5.0%，7.5%和10.0%的方式提高有机负荷（OLR），在高温（55±1）℃条件下开展鸡粪长期甲烷发酵实验并测定了各阶段污泥的比产甲烷活性（SMA），探究氨氮浓度对鸡粪高温甲烷发酵的影响.结果显示，当进料TS由5.0%增至10.0%，出料氨氮浓度由（2.5±0.3）g/L增至（6.1±0.2）g/L，挥发性脂肪酸（VFAs）由（0.4±0.1）g/L增至（26.1±1.5）g/L，pH值由（8.3±0.2）降至（6.9±0.1），产气率由（267.2±12.5）mL/g TS_in降至49.8±8.2mL/g TS_in，甲烷浓度由（67.2±1.3）%降至（36.0±1.7）%.长时间采用TS 10.0%的进料浓度，发酵系统中氨氮浓度最高达到7.5g/L，VFAs浓度达到27.0g/L，产气下降明显.氨氮抑制鸡粪高温甲烷发酵产气的初始浓度为2.5~3.0g/L.进料TS大于7.5%，鸡粪高温甲烷发酵会受到氨氮抑制.氨氮浓度的升高导致高温发酵体系利用乙酸产甲烷的能力降低，氨氮浓度达到5.5g/L，SMA降低60.0%；氨氮浓度达到7.0g/L，污泥利用乙酸产甲烷的活动几乎停止.

Effect of feed concentration on long-term thermophilic methane fermentation of chicken manure

Effect of improved feed concentration, which lead to ammonium accumulation, on chicken manure methane fermentation under thermophilic condition (55±1)℃was investigated by using an integrated approach in a laboratory-scale semi-continuously stirred tank reactors. The reactor operated for 267days at a fixed hydraulic retention time of 20days, with feed concentration based on total solid increased from 5.0% to 7.5% and 10.0%. With feed concentration increased from 5.0% to 10.0%, the ammonia concentration increased from (2.5±0.3) g/L to (6.1±0.2)g/L, the volatilized fatty acids (VFAs) increased from (0.4±0.1)g/L to (26.1±1.5)g/L, when pH value, biogas production rate and methane content dropped from (8.3±0.2) to (6.9±0.1), from (267.2±12.5)mL/g TS_in to (49.8±8.2)mL/g TS_in and from (67.2±1.3)% to (36.0±1.7)%, respectively. The highest ammonia concentration of 7.5g/L and highest VFAs concentration of 27.0g/L were achieved at 197^th day when the feed concentration elevated to 10.0%, causing obvious inhibition on methane fermentation system. The effect of ammonia accumulation on biogas production and VFAs accumulation was analyzed using the method of linear cumulative effect. It was said that the initial ammonia concentration of 2.5~3.0g/L will inhibit the thermophilic digestion of chicken manure. The biogas production would be decrease or ceased when the feed concentration greater than 7.5%. During the operation, the specific methanogenic activity (SMA) test was carried out with sodium acetate as substrates. At feed TS concentration of 7.5% and 10%, ammonia concentration of 5.5 and 7.0g/L caused a drop in SMA by 56.0% and 100%, respectively.