Enhanced phenol degradation under different shock-stress in LAC/AS system: The combination effects of LAC toxicity mitigation and microbial community shift

The lignite activated coke-facilitated activated sludge (LAC/AS) process has proved to be an effective method for increase of phenol biodegradability, yet the interactions between LAC toxicity mitigation and microbial community shift remain unclear. In this study, the phenol degradation rate under different shock-stress for 51 days were investigated. LAC/AS system can tolerate higher phenol shock stress but phenol removal rate starts to descend at 200 mg/L. The system settling performance deteriorated as the filamentous bulking appeared after 40 days but the phenol removal rate was maintained. The results indicated that the microbial community tend to shift for phenol biodegradation when the effect of LAC toxicity mitigation subdued. However, the SVI increased sharply from 40 to 226 mL/g in a relatively long operation period along with the increase of floc size and reduction of TB EPS. Flavobacterium and Bacteroides were the dominated species in the LAC/AS bulking system, correlating to the sustained phenol removal. This work enhances our understanding on the interactions between LAC and microbial community in LAC/AS system, which can be employed for further optimizing LAC/AS technology.

Automated summary

The study found that the LAC/AS system can tolerate higher phenol shock stress, but the removal rate begins to decrease at 200 mg/L. Despite the appearance of filamentous bulking after 40 days, the system maintained its phenol removal efficiency. The microbial community tends to shift for phenol biodegradation when the effect of LAC toxicity mitigation weakens, indicating the need for further optimization of LAC/AS technology.