Effect of extracellular enzyme activity on digestion performance of mesophilic UASB reactor treating high-strength municipal wastewater

Effect of extracellular enzyme activity on digestion performance of up-flow anaerobic sludge blanket (UASB) reactor was investigated for enhancement of anaerobic treatability of municipal wastewater. Two identical UASB reactors (9 L), namely Reactor-A (without enzyme addition) and Reactor-B (with enzyme addition), were simultaneously operated at mesophilic conditions (32 ± 2 °C) with a hydraulic retention time of 24 h. Preliminary test results showed that the highest total chemical oxygen demand (TCOD) removal were achieved with an extracellular enzyme dosage of 0.2 mL/L. In the activation period of the extracellular enzyme (on days 186–212), while Reactor-A removed up to 69.3% of TCOD and 55.9% of soluble chemical oxygen demand (SCOD), Reactor-B effectively removed up to 81.9% of TCOD and 72.2% of SCOD. The average VFA/alkalinity ratios were determined to be about 0.40 (±0.03) and 0.28 (±0.08) for Reactor-A and Reactor-B, respectively.