Abstract

A comparison of two bioreactors--ASBR (Anaerobic Sequencing Batch Reactor) and UASB (Upflow Anaerobic Sludge Blanket) reactors was preformed in the experiments. The results show that the performance in the ASBR was better than that in the UASB reactor without a recirculation system at the two temperatures under all organic loading levels. In the ASBR, the soluble COD obtained the reduction of 57%-95% and 70%-93% under an OLR of 2 kg/m 3 d.-20 kg/m 3 .d at room temperature and 35C̕, respectively. In the UASB reactor without a recirculation system, the soluble COD reduction was 49%-78% and 65%-80% under the same OLR with the ASBR at room temperature and 35C̕, respectively. Methane production was measured in the ASBR at both temperatures. Results were close to the theoretical data under an OLR of 2 kg/m 3 .-6 kg/m 3 .d, lower than theoretical data under an OLR of 8 kg/m 3 .d-20 kg/m 3 .d. VFA concentrations in both reactor effluents increased with an increase in the OLR under all loading levels at the two temperatures. Both reactors could maintain the biomass inside the reactor so as to achieve low VSS levels in both reactor effluents throughout the whole experiment. In many full-scale or lab-scale experiments, the UASB reactor is operated with or without recirculation system, and the ratio of recirculation to feed is changed from 0 to 10. Based on the obtained results of soluble COD reduction in the UASB reactor without recirculation, under an OLR of 6 kg/m 3 .d to 20 kg/m 3 .d at room temperature and 8 kg/m 3 .d to 20 kg/m 3 .d at 35C̕, the UASB reactor requires a recirculation system; the ratio of recirculation to feed was also modelled in this study.