Oxygen-limited aeration for relieving the impact of phenolic compounds in anaerobic treatment of coal gasification wastewater

• Recovery strategy was to tackle shock loading in the EB-GAC reactor treating CGW.
• Oxygen-limited aeration and addition of PAC were the efficient recovery strategies.
• Oxygen-limited aeration reduced microbial inhibition and restored sludge activity.

Anaerobic digestion is an efficient tool for improving aerobic biodegradability of coal gasification wastewater, but the shock loading usually results in a failed performance of the anaerobic process. The oxygen-limited aeration was conducted to handle the impact of coal gasification wastewater in an anaerobic expanded-bed GAC reactor. Results indicated that the oxygen-limited aeration of 0–0.5 mgO2/L could shorten the recovery time from 23 to 11 days under natural condition, and the addition of 1 g/L PAC could reduce the recovery time to 14 days. The corresponding removal efficiencies of COD and phenolic compounds could increase to above 60 and 50%, respectively. The phenol utilization rates of sludge reached 83.9 ± 5.7 mg phenol/(g VSS d) after recovery of reactor performance by using oxygen-limited aeration, and only 70.4 ± 3.8 mg phenol/(g VSS d) by using natural recovery and 65.2 ± 5.9 mg phenol/(g VSS d) by using PAC addition. The recovery strategy of oxygen-limited aeration might be helpful to relieve the inhibitory effect of phenolic compounds and restore metabolic activity of anaerobic bacteria.