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

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Abstract
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°C and at hydraulic loads as high as 2 m3 · m−3 · 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 m3 · PE−1 · year−1, and the excess sludge production ranges form 5.0‐8.6 kg TS · PE−1 · 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.