Novel insight into the degradation of polyacrylamide by thermophilic anaerobic digestion

Polyacrylamide (PAM) is a commonly used flocculant for sludge dewatering in wastewater treatment plants. The degradation of PAM has been proved by anaerobic digestion (AD) however, the effect of PAM on AD under the thermophilic condition at various pH has not been studied yet. The current study investigated the degradation of PAM during the AD process under thermophilic conditions. The results showed that the PAM at the concentration of 10 g/kg TSS depicted a 60% degradation in control and an accelerated rate of 70% in TR-II (pH 9) within fifteen days. The production of VFAs in the blank reactor was 3826 ( +/- 137) mg COD/L which was 1.2-fold higher than the control (3224 ( +/- 143)). Similarly, a higher VFA production of 3452( +/- 172.6) mg COD/L was observed in TR-II than in TR-I (3074 ( +/- 153.7)). The optimal methane production was 261 mL/g VS, 181 mL/g VS, 172 mL/g VS, and 193 mL/g VS in the blank, control, TRI, and TR-II respectively. The Gompertz model and the modified Gompertz model were excellently fitted to the results of TR-I and TR-II with R2 values of 0.996 and 0.997 respectively. This study is of great importance for understanding and application of thermophilic AD in wastewater treatment plants.