The persistence and transformation of trace organic chemicals (TOrCs) through wastewater treatment (WWT) systems is of interest due to their possible impacts on human and environmental health. Traditionally biological WWT processes were not designed to treat TOrCs. Membrane bioreactor (MBR) technology is an advanced treatment technique desirable for its flexibility, compactness, and combination of biological treatment and filtration processes. Investigation of MBR’s ability to remove TOrCs has largely focused on aerobic processes and relied on targeted or suspect screening approaches for analytical analyses, which can miss potentially important unknown or unexpected chemicals. This research uses a comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS) based nontargeted approach, to provide a more comprehensive comparison of aerobic and anaerobic MBRs for treating TOrCs in domestic wastewater. Two laboratory-scale AeMBR and AnMBR systems were operated and maintained in parallel. While both systems shared one feed tank, the biological treatment steps (bioreactors) for the AeMBR and AnMBR utilized an aeration tank (with activated sludge) and an anaerobic baffled reactor, respectively. Composite samples corresponding to the hydraulic retention times were collected from the feed, bioreactor effluents, and membrane permeates. Fluorescence and general water quality parameters such as chemical oxygen demand, total suspended solids, and nutrients were assessed. For nontargeted analysis, samples were extracted and concentrated, then analyzed by GC×GC/TOF-MS followed by ChromaTOF statistical compare analysis. Additionally, a hierarchal clustering analysis was performed. Total number of GC peaks detected per sample, as well as a semi-quantitative evaluation of a subset including 1,095 chemicals will be reported. These 1,095 chemicals were classified into several groups: persistent compounds, removed compounds, and transformation products. Of the 1,095 chemicals discussed, 353 chemicals were tentatively identified with high confidence and an additional physicochemical analysis using available data on their molecular descriptors is in progress and will be presented. This research may uncover chemicals not previously known to be present in WWT systems and help us better understand potential removal mechanisms in AeMBR and AnMBR treatment.

Evaluating aerobic versus anaerobic membrane bioreactors’ for treating trace organic chemicals using GC×GC/TOF-MS based non-targeted approach

ACS Spring 2022

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