Influence of NOM and SS on the BPA removal via peroxidase catalyzed reactions: Kinetics and pathways

In the present study, horseradish peroxidase (HRP) was employed to removal bisphenol A (BPA) with the presence of natural organic matter (NOM) and suspended solids (SS). Humic acid (HA) and kaolin have been selected as the typical NOM and SS in the experiment. According to the results, HA has shown a very interesting performance, which has both inhibitory and facilitation effects on BPA removal. For the low enzyme concentration (20 u/L and 50 u/L), small amount of HA could facilitate the BPA removal, while large amount of HA could inhibit the BPA removal. For the higher enzyme concentration (100-300 u/L), the addition of HA reduced the removal transformation of BPA and the inhibition effect of HA raised with the increase of HA concentrations. The facilitation nature of HA on enzyme catalytic processes can be attributed to the mitigation of enzyme inactivation, which has been proven by HRP inactivation rate. The inhibitory effect could be caused by the inhibition effect of HA on the enzyme activity, which has been suggested by both kinetic study and enzyme inactivation analysis. Kaolin showed a negative effect on BPA removal by HRP catalyzed reactions due to the inhibition effect of kaolin on HRP activity. The results have important implications for the engineering design by employing HRP in water and waste water treatment. (C) 2016 Elsevier B.V. All rights reserved.