Treatment of coal gasification wastewater by a two-continuous UASB system with step-feed for COD and phenols removal

摘要

A two-continuous mesophilic (37±2°C) UASB system with step-feed was investigated as an attractive optimization strategy for enhancing COD and total phenols removal of the system and improving aerobic biodegradability of real coal gasification wastewater. Through the step-feed period, the maximum removal efficiencies of COD and total phenols reached 55-60% and 58-63% respectively in the system, at an influent flow distribution ratio of 0.2 and influent COD concentration of 2500mg/L; the corresponding efficiencies were at low levels of 45-50% and 43-50% respectively at total HRT of 48h during the single-feed period. The maximum specific methanogenic activity and substrate utilization rate were 592±16mg COD-CH_4/(gVSSd) and 89±12mg phenol/(gVSSd) during the step-feed operation. After the anaerobic digestion with step-feed, the aerobic effluent COD concentration decreased from 270±9 to 215±10mg/L. The results suggested that step-feed enhanced the degradation of refractory organics in the second reactor.