Response of activated sludge microbial communities to influent quality shock loading and corresponding process control

This study took a large municipal wastewater treatment plant （WWTP） in northern China as the research object， and systematically investigated the influence characteristics and response mechanism of abnormal influent shock load on the structure of activated sludge microbial community. The results showed that influent shock caused drastic changes in the structure of activated sludge microbial community： the abundances of core functional flora such as Proteobacteria and Bacteroidetes decreased significantly by 55.30% and 44.35%， respectively； the community diversity was reduced， the nitrification function was weakened， and the concentration of effluent ammonia nitrogen increased. Meanwhile， shock-resistant flora such as the genus SJA-28 within Chlorobi proliferated rapidly， showing a 5.68‑fold increase in relative abundance compared to the normal period， which helped sustain the pollutant removal capacity of the system to some extent. These findings confirmed that the activated sludge system has strong shock resistance and self-recovery capacity. The implementation of regulatory measures such as shortening sludge retention time （SRT） and increasing the dosage of sodium acetate and phosphorus removal chemicals was shown to be conducive to the rapid recovery of functional flora. Based on these findings， it is suggested that in practical operation， SRT adjustment strategies should be flexibly adjusted according to influent quality characteristics and temperature conditions， so as to improve the stability and resilience of the wastewater treatment system in responding to shock loading.