Abstract: In order to improve the performance of internal circulation(IC) reactor in which granular sludge had formed, an additional external circulation device was added to the reactor. The operation stability of this system was investigated at various reflux ratios of 0, 1.0, 2.0, 3.0 and 4.0. Compared with without external circulation situation, additional device do not indeed damage anaerobic conditions inside the IC reactor and the reactor operation was stable at given range of reflux ratio. When chemical oxygen demand(COD) of influent was 6000 mg·L^-1, hydraulic retention time(HRT) about 10h, and volume loading 14 kg·m^-3·d^-1, the MLSS of system (mixed liquid suspended solids) and the removal rate of COD increased with the growth of reflux ratio, and could reach the maximum 97.3% and the lowest COD of effluent 160 mg·L^-1 respectively. With increase of reflux ratio, the total quantity of biogas produced increased to 171.2 L·d^-1. The methane production increased at the beginning and then maintained stabilization, and was 91.7 L·d^-1 at reflux ratio 2.0. Remarkably, biodiversity in granular sludge had been improved due to additional external circulation. After the system with additional external circulation operated for a period of time, the dominant bacteria for methane production changed from Methanobacterium to Methanococcus. After comprehensive consideration of energy consumption and COD removal rate, the optimal reflux ratio would be 2.0.

Key words: anaerobic IC reactors, external circulation, granular sludge, reflux ratio, methane, operation efficiency

摘要： 为改善已形成颗粒污泥的IC反应器运行性能，增设外循环装置，并在回流比分别为0、1.0、2.0、3.0、4.0的情况下，进行了系统运行稳定性研究。与无外循环的情况相比，在设定的回流比范围内，附加外循环不会破坏反应器内部厌氧条件，反应器运行稳定；在进水COD为6000 mg·L^-1左右，系统HRT约为10 h，容积负荷为14 kg·m^-3·d^-1的情况下，系统污泥MLSS有所增加，COD去除率随回流比的增大而增加，最高可达97.3%，出水COD低至160 mg·L^-1；随回流比的增大，产气总量逐渐增加且最终可达171.2 L·d^-1，甲烷产量先增加后趋于稳定，在回流比为2.0时可达到91.7 L·d^-1；增加外循环运行一段时间后，厌氧颗粒污泥生物相更为丰富，产甲烷优势菌由甲烷杆菌转变为甲烷八叠球菌。结合能耗和去除效率等考虑，回流比为2.0时最佳。

关键词: 厌氧IC反应器, 外循环, 颗粒污泥, 回流比, 甲烷, 运行效果