Application of aerobic granular sludge in polishing the UASB effluent.

Stable aerobic granules were successfully developed in a sequencing batch reactor (SBR) fed with glucose and sodium acetate as the main carbon sources, and then en they were acclimatized to polish the effluent from an up-flow anaerobic sludge blanket (UASB) reactor. It was found that more than 95% chemical oxygen demand (COD) and 85% suspended solids (SS) in the UASB effluent could be removed by an aerobic granular SBR as a post treatment unit. The performance of the SBR was stable over the whole experimental period. At an organic loading rate (OLR) of 4.5 to 5.4 g 1(-1) d(-1), the acclimatized aerobic granules had an average diameter of 3.5 to 6.0 mm and a minimal settling velocity of 72 in m h(-)1. The biomass concentration in the SBR was as high as 8.4 g (dry weight) 1(-1). This study showed for the first time that aerobic granular sludge in SBR Would be an effective means to polish the effluent from UASB reactor.