Rapid granulation and sludge retention for tetrachloroethylene removal in an upflow anaerobic sludge blanket reactor

A laboratory scale upflow anaerobic sludge blanket (UASB) reactor was operated at 35 °C for over 200 days to investigate the granulation mechanism during tetrachloroethylene (TCE) biodegradation. Anaerobic, unacclimated sludge and glucose were used as seed and primary substrate, respectively. TCE-degrading granules developed after 1.5 months of start-up. They grew at an accelerated pace for 7 months. The TCE-degrading granules had a maximum diameter of 2.5 mm and specific methanogenic activity of 1.32 g chemical oxygen demand (COD) g−1 total suspended solid (TSS) day−1. 94% COD and 90% TCE removal efficiencies were achieved when the reactor was operating at loading rates as high as 160 mg TCE l−1 day−1 and 14 g COD l−1 day−1, after 230 days of continuous operation.