Acidogenic Fermentation Facilitates Anaerobic Biodegradation of Polycyclic Aromatic Hydrocarbons in Waste Activated Sludge

The anaerobic biodegradation of phenanthrene (PHE), a typical polycyclic aromatic hydrocarbon (PAH) in waste activated sludge (WAS), during acidogenic fermentation created by alkaline pHs and biosurfactant was examined in this study. The anaerobic biodegradation efficiency of PHE increased from 17.6% with an operation time of 8 days in the control to 47.5% at pH 10.0, and to 78.2% under the conditions of pH 10.0 and 0.3 g alkyl polyglucose (APG) per gram of total suspended solids (TSS) with a mineralization rate of 25.1%. A mechanistic exploration indicated that the bioavailability of PHE was remarkably improved because of the disruption of sludge structure, and enhancement of transfer and sorption by bacteria and transmembrane transport into microbial cells by alkaline pH and APG. Under acidogenic conditions, the abundance of key microorganisms, especially typical acidogenic bacteria that were capable of degrading PHE, activities of key microbial enzymes, and quantities of functional genes were benefitted by PHE biodegradation. The protein released from WAS facilitated electron transfer among microorganisms and stimulated the cometabolism of PHE. Possible pathways of PHE biodegradation under acidogenic conditions were presented.