Energy regeneration of hydrolyzed polyacrylamide-containing wastewater in anaerobic activated sludge biosystem: Biohydrogen, extracellular polymeric substances and functional microorganisms

How to utilize the organic residues of industrial wastewater to achieve subsequent value-added energy recovery is a top priority in wastewater treatment. Currently, the bioconversion of hydrolyzed polyacrylamide (HPAM)-containing wastewater to biohydrogen (BioH2) is currently unknown and requires further study. Influent HPAM level played a key role in bioH2 production, extracellular polymeric substance (EPS) intensity and microbial interaction. As the influent HPAM level increased from 100 to 500 mg·L−1, HPAM biodegradation concentration rose from 82.6 to 359 mg·L−1, and the bioH2 output improved from 0.38 to 0.504 mL·mg−1HPAM. Acetate, propionate, butyrate and valerate appeared as typical metabolite volatile fatty acids (VFAs) in anaerobic activated sludge biosystem. Acetate content kept an upward tendency from 20.3 to 88.3 mg·L−1 and butyrate content went up from 5.42 to 23.5 mg·L−1 and the total VFA production grew up from 27.1 to 118 mg·L−1 as the influent HPAM level elevated. Tyrosine/tryptophan proteins dominated key advantage in all EPS types. The fluorescence intensity of EPS showed a rapidly increasing trend with the elevation of influent HPAM level. Pseudomonas, Bacillus, Clostridium, Acetobacter, Enterobacter, Xanthomonas, Citrobacter, Actinomyces, Sporolactobacillus, Streptococcus, Veillonella, Butyrivibrio and Klebsiella fulfilled the function of bioH2 production from those biosystems. Those bioH2-generating functional bacteria were associated with HPAM biotransformation, bioH2 yield, VFA production and EPS intensity in the anaerobic activated sludge biosystem with different influent HPAM level. Finally, bioH2 production from HPAM-containing wastewater was assessed from the economic perspective. This study realizes the energy regeneration of HPAM-containing wastewater bioconversion to bioH2, which is of great practical significance and application value for oilfield output wastewater treatment.