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Quantification of Trace Anthropogenic Compounds in Reclaimed Wastewater
Civil and Environmental Engineering
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Reclaimed wastewater contains trace anthropogenic compounds that are poorly removed during conventional wastewater treatment. Notable reclaimed wastewater applications include supplementing drinking water supplies and crop irrigation. This thesis aims to quantify N-nitrosodimethylamine (NDMA), NDMA precursors, and pharmaceuticals and personal care products (PPCPs) from reclaimed wastewater applications as an indication of anthropogenic impact. The applications include aquifer storage and recovery (ASR) and crop irrigation using gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. NDMA and NDMA precursors were quantified in a treated wastewater effluent-fed recharge utility applying ASR in two sampling events from March 2017 and August 2018. Lagrangian sampling was applied for microfiltration effluent, reverse osmosis effluent, ultraviolet radiation (UV) feed, and UV product for both events in the recharge utility. Solid-phase extraction (SPE) was applied to concentrate NDMA and NDMA precursors. NDMA formation potential (FP) tests were performed to indirectly determine NDMA precursor concentration. NDMA and NDMA precursor concentration decreased after microfiltration across both events by greater than 93% and 89%, respectively. Permeate from older RO membranes contained 31% more NDMA and 14% more NDMA precursor concentration than newer membrane permeate.Another reclaimed wastewater scheme studied was crop irrigation. This releases PPCPs to agricultural soils where they can be taken up by plants in the transpiration stream. Dry mass concentration of nine PPCPs were quantified in field-grown alfalfa irrigated with treated wastewater, groundwater-irrigated crops from private farms, and market-sourced produce. For the PPCPs quantified, field-grown alfalfa had a dry mass concentration range of 0.03-54 ng g-1, groundwater-irrigated crops had a range of 0.03-62 ng g-1, and market-sourced produce had a range of 0.04-162 ng g-1. Neutral compounds more readily accumulated compared to compounds that were ionized at environmental pH, indicating that PPCP uptake was likely related to physicochemical properties. Preliminary health impacts associated with consumption of affected market produce were estimated from acceptable daily intake. Negligible health impacts were typically found due to low PPCP concentration in market produce. PPCP transport from crop irrigation to different environmental compartments was estimated using EPI Suite. Compounds with low sorption potential and long half-lives could transport to groundwater whereas compounds with intermediate to high sorption potential were predicted to accumulate in plants or remain in the soil. The approach implemented to quantify NDMA and PPCPs in different environmental media indicates that trace anthropogenic compound transport depends on the reclaimed wastewater application and compound physicochemical properties.