Ultraviolet membrane bioreactor for enhancing the removal of organic matter in micro-polluted water

Abstract

This research investigated the organic matter removal performance using an ultraviolet (UV) treatment membrane bioreactor (UV–MBR) in micro-polluted surface water. Compared with a conventional MBR process, the UV–MBR achieved higher removal efficiencies in terms of the reduction of CODMn and UV254, which were reduced by 58 and 63%, respectively. The organic matter removal rate increased significantly arising from biodegradation mechanisms. Furthermore, the ammonia nitrogen and nitrite nitrogen were removed almost completely and not affected by the subsequent UV treatment. Through the UV treatment, a fraction of refractory organics was transformed into biodegradable organics available to the microbial consortium in the reactor. UV treatment of the raw water leads to an increase of BDOC content from 0.22 to 0.88 mg L−1 after 5 d inoculation. According to the analysis of the characteristics of hydrophobic/hydrophilic compounds, the relative molecular weight distribution and the fluorescence excitation–emission matrix of the organics, it can be indicated that the organics were transformed into biodegradable organics because part of molecules were split into simple structures during the UV treating process. Furthermore, the organics removed by the UV–MBR were hydrophobic fractions.