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In this study, we demonstrate the potential of an osmotic membrane bioreactor (OMBR)-membrane distillation (MD) hybrid system for simultaneous wastewater reuse and seawater desalination. A stable OMBR water flux of approximately 6 L m-2 h-1 was achieved when using MD to regenerate the seawater draw solution. Water production by the MD process was higher than that from OMBR to desalinate additional seawater and thus account for draw solute loss due to the reverse salt flux. Amplicon sequencing on the Miseq Illumina platform evidenced bacterial acclimatization to salinity build-up in the bioreactor, though there was a reduction in the bacterial community diversity. In particular, 18 halophilic and halotolerant bacterial genera were identified with notable abundance in the bioreactor. Thus, the effective biological treatment was maintained during OMBR-MD operation. By coupling biological treatment and two high rejection membrane processes, the OMBR-MD hybrid system could effectively remove (> 90%) all 30 trace organic contaminants of significant concern investigated here and produce high quality water. Nevertheless, further study is necessary to address MD membrane fouling due to the accumulation of organic matter, particularly protein- and humic-like substances, in seawater draw solution.

The bacterial community in different redox regimes of an anoxic-aerobic MBR under different operating conditions was investigated using pyrosequencing. With internal recirculation (IR) between the anoxic and aerobic reactors, the bacterial communities in these reactors were highly similar in structure and phylogenetic relationship, indicating IR as a key driving force shaping the bacterial communities that are responsible for the core function in the system. Without IR, each redox condition sustained the growth of distinct bacterial communities according to their oxygen requirement, and the anoxic community presented a low capacity of nutrient and trace organic contaminant (TrOC) removal. Higher bacterial diversity under longer sludge retention time (SRT) was evident; however, except for a few TrOCs, removal efficiency of TOC, TN and TrOCs were the same irrespective of the SRT. The presence of TrOCs induced shifts in bacterial communities, and a correlation between bacterial communities and TrOC transformation was noted. The important candidates for TrOC biotransformation were the taxa within Proteobacteria, particularly Methylophilales and Myxococcales. Other bacterial groups potentially contributing to TrOC biotransformation were those related to nitrogen removal, such as Rhodocyclales and Plantomycetes. In contrast, the detected members of Cytophagaceae (Bacteroidetes) appeared not to contribute to TrOC biotransformation.

The occurrence of a broad spectrum of trace organic contaminants (TrOCs) in raw sewage from a small resort town and their removal by a full- and a pilot-scale membrane bioreactor (MBR) was analysed in this study. The MBR systems demonstrated similar reduction of chemical oxygen demand. However, the full-scale MBR sustained higher and more stable nutrient removal (>95% for both total nitrogen, TN and phosphate, View the MathML sourcePO43−-P) than the pilot-scale system (ca. 80% TN and 30% View the MathML sourcePO43−-P removal). Of the 45 monitored TrOCs including pharmaceuticals and personal care products (PPCPs), industrial chemicals, steroid hormones, and pesticides, 41 compounds were detected in the raw sewage above detection limits of 5-20 ng L−1. A correlation between the removal of TN and eight TrOCs (atenolol, caffeine, naproxen, ibuprofen, gemfibrozil, DEET, estrone and diuron) was observed. Additionally, the full-scale MBR demonstrated higher and/or more stable removal for sulfamethoxazole, trimethoprim, diclofenac, diuron and amitriptyline. With the exception of caffeine, estrone and triclosan, TrOC concentrations in MBR effluent were lower than the Australian Guidelines for Water Recycling: Augmentation of Drinking Water Supplies.

The impacts of four simulated hazardous events, namely, aeration failure, power loss, and chemical shocks (ammonia or bleach) on the performance of an anoxic-aerobic membrane bioreactor (MBR) receiving real wastewater were investigated. Hazardous events could alter pH and/or oxidation reduction potential of the mixed liquor and inhibit biomass growth, thus affecting the removal of bulk organics, nutrients and trace organic contaminants (TrOC). Chemical shocks generally exerted greater impact on MBR performance than aeration/power failure events, with ammonia shock exerting the greatest impact. Compared to total organic carbon, nutrient removal was more severely affected. Removal of the hydrophilic TrOCs that are resistant and/or occur at high concentrations in wastewater was notably affected. The MBR effectively reduced estrogenicity and toxicity from wastewater, but chemical shocks could temporarily increase the endocrine activity of the effluent. Depending on the chemical shock-dose and the membrane flux, hazardous events can exacerbate membrane fouling.