Anaerobic treatment of raw domestic sewage at ambient temperatures using a granular bed UASB reactor.

Results obtained in a 120 liter 2 m high UASB-reactor with raw domestic sewage and using a granular sugar beet waste cultivated seed sludge, reveal the feasibility of this type of anaerobic treatment for domestic sewage. Under dry weather conditions 65-85% COD reduction can be achieved at temperatures in the range of 8-20 degrees C and at hydraulic loads as high as 2 m(3) x m(-3) x day(-1). In the case of heavy rainfall the COD-reduction drops to 50-70% and occasionally, viz.at very low influent COD, even below 50%. The net methane production amounts to 7.1-7.3 m(3) x PE(-1) x year(-1), and the excess sludge production ranges form 5.0-8.6 kg TS x PE(-1) x year(-1). Regarding the results obtained anaerobic treatment of raw sewage not only looks an attractive proposition for tropic areas but also for moderate climatic areas.