Metagenomic analysis reveals the effects of potassium ferrate and steel slag on fate of ARGs in anaerobic sludge digestion system

Waste activated sludge (WAS) pose a potential risk for the spread of antibiotic resistance genes (ARGs). This study estimated the effect of sludge on antibiotic resistance genes (ARGs) in anaerobic sludge digestion process. Metagenomic analysis revealed anaerobic sludge with potassium ferrate (PF) and the modified PF loaded steel slag (MPF-SS) brought an increase of ARGs during digestion process. PF was found to effectively reduce most of the high-risk ARGs (i.e., acrB and mexW). Furthermore, network and correlation analysis among ARGs and genera verified that PF significantly increased the potential ARGs hosts. Mechanistic analysis revealed that PF induced oxidative stress behavior of anaerobic digestion microorganisms, and observably upregulated the relative genes about SOS response-related. These findings provide insights into the mechanism underlining PF for ARGs fate and its risk during anaerobic sludge digestion, which could offer practical guidance on the sustainable management of WAS.