Predicting the fate of emerging trace organic contaminants of concern during MBR treatment based on their molecular properties

摘要

We demonstrate that the fate of emerging trace organic contaminants during membrane bioreactor (MBR) treatment can be qualitatively predicted by assessing their molecular properties. This work further expands the qualitative framework for the prediction of trace organic removal by MBR treatment reported in our recent study [1]. A set of 30 emerging trace organic contaminants was selected for this investigation. The removal efficiency of some of these emerging trace organics by MBR have not been previously reported in the literature. Examples include phytoestrogens (such as enterolactone and formnonetine) and UV filters (such as benzophenone, oxybenzone, and octocrylene) which are frequently found at trace levels in natural water and raw sewage in Australia [2-3]. A laboratory scale MBR system was used in this study (Figure 1). The MBR system was equipped with an external ceramic membrane module (nominal pore size of 0.1 μm), a temperature control unit, a glass reactor (of 5 L of active volume), air pump, and influent and effluent pumps which were controlled by a personal computer. The MBR system was seeded with sludge obtained from the Wollongong Wastewater Treatment Plant in Wollongong, Australia. A synthetic wastewater was used in this study and the composition of this synthetic wastewater is available elsewhere [4]. After over 100 days of acclimatisation, trace organic contaminants were continuously introduced into the synthetic wastewater each at a concentration of approximately 5 ug/L. The MBR system was operated under a constant condition with the hydraulic retention time, temperature, dissolved oxygen concentration, and mixed liquor pH of 26 h, 25.8 ± 0.3 °C, 2.3 ± 0.3 mg/L, and 7.2 ± 0.3, respectively. The mixed liquor suspended solid concentration in the reactor was maintained at 5.0 ± 0.5 g/L by withdrawing the excess sludge every 3-4 days, resulting in a sludge retention time of approximately 88 days.