Tetrachloroethylene (TCE) removal during anaerobic granulation in an upflow anaerobic sludge blanket (UASB) reactor

The anaerobic biotransformation of TCE was investigated during the granulation process by reducing the HRT and increasing the chemical oxygen demand (COD) and TCE loadings in a 21 laboratory-scale upflow anaerobic sludge blanket (UASB) reactor. Anaerobic unacclimated sludge and glucose were used as seed and primary substrate, respectively. Initial granules were developed after 1.5 months of start-up, which grew at an accelerated pace for 7 months and then became fully grown. The effect of operational parameters such as influent TCE concentrations, COD and TCE loading, food to microorganism (F/M) ratio and specific methanogenic activity (SMA) were also considered during granulation. The granular sludge cultivated had a maximum diameter of 2.5mm and SMA of 1.32gCOD(gTSSday)(-1) while 94% COD and 90% TCE removal efficiencies were achieved when the reactor was operating at loading rates as high as 160mgTCE(lday)(-1) and 14gCOD(lday)(-1), respectively after 230 days of continuos operation. This corresponds to HRT of 0.28 day and F/M ratio of 0.60 gCOD (gTSS day)(-1). Kinetic coefficients of k (maximum specific substrate utilization rate), K-s (half velocity coefficient), Y (growth yield coefficient) and b (decay coefficient) were determined to be 2.38 mgCOD (mgTSS day)(-1), 108mgCODl(-1), 0.17mgTSS(mgCOD)(-1) and 0.015 day(-1), respectively during TCE biotransformation based on glucose-COD during granulation.