Anaerobic treatment of domestic wastewater in a membrane-coupled expended granular sludge bed (EGSB) reactor under moderate to low temperature

The performance of an expended granular sludge bed (EGSB) reactor coupled with hollow fibre membrane filtration for treating domestic wastewater was monitored during 7-month period in the range 11-25 °C, and at the hydraulic retention time (HRT) of 3.5 to 5.7 h. With temperatures above 15 °C, the system was capable of removing 85-96% of total chemical oxygen demand (COD) and 83-94% of total organic carbon (TOC). At 11 °C, increasing HRT from 3.5 to 5.7 h, the total COD removal was increased from 76 to 81%. Applying a higher upflow velocity contributed to better effluent removal efficiency and a higher membrane permeability. The results of tests showed that cake layer resistance was the major resistance. More extracellular polymer substances (EPS) tended to be accumulated on the membrane surface than in the granules since its content was higher on the membrane surface than in the granules.