Photo-biological degradation of Bisphenol A, UV/ZnO/Iodide process at the center of biological reactor

Abstract

The goal of this study is to achieve zero waste with UV/Iodide/ZnO (UIZ)-based photocatalytic-biological reactor (IPBR) containing baffles was devised to degrade Bisphenol A (BPA), completely. Degradation efficiency of the UIZ, UV/Iodide, UV/ZnO, and only UV processes were determined as 97.4%, 78.4%, 71.4% and 51% respectively (reaction time: 30 min, BPA concentration: 200 mg L−1 and pH 7). According to additional study, the optimal Molar ratio was obtained 0.87:1:50 of Iodide /ZnO/BPA. Analyzing effluents of the UIZ reactor by liquid chromatography–mass spectroscopy after 5, and 10 min reaction time revealed that BPA decomposes to ring-shaped compounds convert to linear compounds within 10 min reaction time. Pseudo first-order kinetic model demonstrated that the observed rate constant (kobs) increased from 0.0728 to 0.1186 min-1 and the observed BPA degradation rate (robs) increases from 3.64 to 23.72 mg L-1 min-1 with increasing the BPA concentration. Meantime, the EEO (Electrical energy per order) values calculated according to the kinetics model results decreased from 11.60 to 7.12 kWh m-3, respectively (with the increase of BPA concentration from 50 to 200 mg L-1). Analysis of effluent dilution effect and toxicity assessment on Escherichia coli exhibited that no growth inhibition in presence of effluents that have been extracted after 10 min BPA degradation even after long incubation periods. Finally, feeding effluents of the UIZ photoreactor to biological treatment helped to reduce COD levels of 100, 200 and 300 mg L-1 BPA solutions to almost zero after 5, 9, 14 h aeration, respectively. Therefore, the proposed photo catalyst-biologic process is a promising technology for complete treatment of BPA containing wastewaters.