Synchronous achievement of sludge reutilization, carbon emission reduction and N2O mitigation through partial denitrification driven by periodate-pretreated sludge fermentation

A novel strategy for achieving partial denitrification (PD) driven by sludge fermentation products (SFPs) based on periodate (PI) pretreatment was proposed. Results showed that PI pretreatment significantly enhanced short-chain fatty acids (SCFAs) yield by promoting waste activated sludge (WAS) disintegration and substrate conversion while stimulating the activity of acidogenic bacteria. Specifically, the maximal SCFAs yield increased from 552.5 ± 16.3 to 3219.0 ± 37.4 mg COD/L with PI dosage increasing from 0 to 0.25 g/g TSS. In batch tests, PD driven by 0.05 g PI/g TSS-pretreated SFPs fermentation exhibited excellent performance, achieving higher nitrite (NO 2 − -N) accumulation (22.7 mg/L) and nitrate transformation ratio (97.26 %) compared to other PI-pretreated SFPs. Remarkably, compared with sodium acetate as the carbon source, SFPs reduced N 2 O emissions during denitrification by 35.6 %–52.7 %. Linear discriminant analysis of effect size (LEfSe) indicated that PI pretreatment selectively enriched fermentative functional bacteria. Metagenomic analysis revealed that PI pretreatment significantly upregulated the expression of key functional genes involved in hydrolytic and acidogenic pathways, while inhibiting methanogenesis-related genes. Particularly, the PI-pretreated SFPs exhibited superior multi‑carbon metabolic pathways, causing more electron flow toward nitrate reduction, thereby confirming the outstanding NO 2 − -N accumulation capacity in the PD. Furthermore, the addition of 0.05 g PI/g TSS reduced the total abundance of antibiotic resistance genes (ARGs) in WAS by 12.7 %, achieving effective ARGs removal. This strategy innovatively enabled both efficient WAS utilization and carbon emission reduction, providing a practical and sustainable approach for the operation of wastewater treatment plants.