Fang Fang

Influent fluctuations are a ubiquitous phenomenon in municipal wastewater treatment plants. However, the underlying mechanism for influent fluctuation on aerobic granular sludge (AGS) pollutant removal performance remains unclear. This research explored the impact of different influent fluctuations for AGS performance by operating four reactors (control group, carbon, nitrogen, and simultaneous carbon-nitrogen fluctuations), and revealed the impact mechanisms by perspective of removal performance, typical cycle tests, carbon allocation analysis, and microbiota characterization. Results indicated that although water quality fluctuation caused certain variations in effluent ammonia and total nitrogen, the fluctuation groups achieved TN removal of 77.83-79.33%, higher than Rc (67.13%). Meanwhile, COD and TP removal of fluctuation groups remained stable at approximately 96% and 90%, respectively. Further analysis revealed that carbon fluctuations promoted the enrichment of DNBs and GAOs, enhanced the expression of denitrification-related genes, leading to improved total nitrogen removal. Nitrogen fluctuations favored GAOs and PAOs/DPAOs, strengthened intracellular carbon storage, resulting in optimal pollutant removal efficiency. Carbon-nitrogen fluctuation enriched DNBs, promoted carbon allocation toward exogenous denitrification, thereby improved nitrogen removal. This study elucidates the mechanisms by which microbial regulation of carbon allocation affects pollutant removal under influent fluctuations. The findings provide fundamental guidance on engineering application of AGS processes under the fluctuating influent conditions.

Polystyrene nanoplastics mitigate Cu-induced stress in Pseudomonas stutzeri by enhancing EPS secretion and nitrogen metabolism gene expression, improving denitrification efficiency. Mechanistic insights are revealed via transcriptomic analysis.