抄録
In order to develop an appropriate technology for sewage treatment in developing countries, a novel process was proposed in this study, which consists of a UASB pre-treatmentunit and the following DHS (Downflow Hanging Sponge-cubes) reactor for polishing up the UASB effluent. The DHS reactor has prominent advantages, in such points as a low-cost and easy-maintenance, because it requires no external aeration input. Our proposed system was installed at a municipal sewage treatment plant site, and its feasibility was evaluated by conducting a long-term experiment with actual sewage as a feed. Three DHS units were in parallel operated at three different modes; R1 was one-through, R2 was addition of the sewage to midpoint, and R3 was an addition of the sewage with recirculation. The proposed whole system verified to perform not only superior organic removal but also excellent nitrification, achieving more than 90% of total-BOD removal and 80% of nitrification at a overall HRT of 8.5hr. Approximately 18% of nitrogen was removed through denitrification in R3-DHS unit. Moreover, DHS reactor exhibited to accomodate a high density of biomass, i. e., 30 g-SS-1-1 sponge volume on average, and the respiration rate was not so low. Over the whole experimental duration no sludge withdrawal was made from all reactors. A simple model accounted for no excess sludge production from the system.
