Kinetics and thermodynamics of hydrolyzed polyacrylamide (HPAM) biodegradation in anaerobic and aerobic activated sludge biochemical treatment systems were explored to determine the maximum rate and feasibility of HPAM biodegradation. The optimal nutrient proportions for HPAM biodegradation were determined to be 0.08 g.L (1) C6H12O6, 1.00 g.L (1) NH4Cl, 0.36 g.L (1) NaH2PO4 and 3.00 g.L (1) K2HPO4 using response surface methodology (RSM). Based on the kinetics, the maximum HPAM biodegradation rates were 16.43385 mg.L (1).d (1) and 2.463 mg.L (1).d (1) in aerobic and anaerobic conditions, respectively. The activation energy (Ea) of the aerobic biodegradation was 48.9897 kJ.mol (1). Entropy changes (DS) of biochemical treatment system decreased from 216.21 J.K (1) to 2.39 J.K (1). Thermodynamic windows of opportunity for HPAM biodegradation were drawn. And it demonstrated HPAM was biodegraded into acetic acid and CO2 under laboratory conditions. Growth-process equations for functional bacteria anaerobically grown on polyacrylic acid were constructed and it confirmed electron equivalence between substrate and product. (C) 2016 Elsevier Ltd. All rights reserved.