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.
Department of Water Pollution Control, De Dreyen 12, 6703 BC Wageningen, The Netherlands.
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Lettinga
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Roersma
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