Flocculation, Anaerobic and Microaerobic Treatment Process of Normal Temperature Low Concentration Domestic Sewage

Domestic sewage was treated by adopting flocculation, anaerobic and microaerobic combined process under normal temperature. The result demonstrates: total hydraulic retention time is 5.5h (chemical flocculation 1.0h, UASB reactor 2.0h and MUSB reactor 2.5h). UASB reactor can achieve anaerobic sludge granulation under normal temperature and is fairly feasible for low concentration domestic sewage treatment. Compared with single stage UASB reactor, hydraulic retention time of flocculation-UASB combined technique reduces from 4h to 2h. COD removal rate rises from 45% to 50%-60% and suspended COD is mainly removed. DO of microaerobic MUSB technique after anaerobic treatment is 0.2mg/L-0.5mg/L with air and water ratio of 1:1. Effluent quality is stable, in accordance with first standard of Synthetical Draining Standard of Sewage, GB8978-1996.