Potential of hydrolyzed polyacrylamide biodegradation to final products through regulating its own nitrogen transformation in different dissolved oxygen systems

Abstract

Potential of hydrolyzed polyacrylamide (HPAM) biodegradation to final products was studied through regulating its own nitrogen transformation. Under the conditions of 2, 3 and 4 mg/L of DO, HPAM removal ratio reached 16.92%, 24.51% and 30.78% and the corresponding removal ratio reached 49.15%, 60.25% and 76.44% after anaerobic biodegradation. NO₃^--N concentration was 9.43, 14.10 and 17.99 mg/L in aerobic stages and the corresponding concentration was 0.17, 0.07 and 0.008 mg/L after anaerobic biodegradation. Oxygen as electron acceptors stimulated the activities of nitrification bacteria and other functional bacteria, thus further enhanced nitrification and HPAM biodegradation. NO₃^- (from HPAM oxidation) as electron acceptors stimulated the activities of nitrate-reducing, acetate-producing and methanogenic microorganisms and they could form a synergistic effect on denitrification and methanogenesis. Thermodynamic opportunity window revealed that NO_x^- could accelerate anaerobic HPAM bioconversion to methane. Aerobic and anaerobic growth-process equations of cells verified that the metabolism on HPAM was feasible.

Keywords: Bioconversion; Cell metabolism; Electron acceptor; Hydrolyzed polyacrylamide; Nitrification and denitrification; Thermodynamic opportunity window.