Megan H. Plumlee

Natural attenuation of pharmaceuticals and alkylphenol polyethoxylate metabolites during river transport: Photochemical and biological transformation

The capacity of rivers to naturally attenuate trace organic compounds is an important but poorly understood process because the many factors that control attenuation are interrelated and difficult to study in isolation. To better understand the relative importance of chemical (photolysis and sorption) and biological attenuation processes, contaminant removal along a 12-km stretch of the Santa Ana River (SAR) was determined as a function of travel time, distance, and irradiance. Target contaminants included three pharmaceuticals (gemfibrozil, ibuprofen, and naproxen) and their metabolites, and the metabolites of alkylphenol polyethoxylates (APEMs). The APEMs included alkylphenols (APs), short-chain alkylphenol polyethoxylates (APEOs), alkylphenol polyethoxycarboxylates (APECs), and carboxyalkylphenol polyethoxycarboxylates (CAPECs). Overall removals ranged from 50% for APs to 100% for naproxen and increased with distance and time, in many cases following first-order kinetics. For naproxen, which is photolabile, average removals were 20 to 30% more during the day than at night; the nighttime and daytime half-lives were 3 h and 1.7 to 1.9 h, respectively. Comparison of field and laboratory data suggests that approximately 40% of the daytime naproxen removal can be attributed to photolysis with the remainder due to other processes, most likely sorption. For ibuprofen and gemfibrozil, half-lives were 5.4 and 2.7 h, respectively, and laboratory data suggest that biotransformation is the principal attenuating process. The APEM attenuation might be due to sorption and biotransformation; phototransformation may also play a minor role. These data demonstrate that travel times on the order of hours can significantly mitigate the impact of effluent discharge on the water quality of shallow rivers.

Perfluorochemicals in water reuse

Faced with freshwater shortages, water authorities are increasingly utilizing wastewater reclamation to augment supplies. However, concerns over emerging trace contaminants that persist through wastewater treatment need to be addressed to evaluate potential risks. In the present study, perfluorinated surfactant residues were characterized in recycled water from four California wastewater treatment plants that employ tertiary treatment and one that treats primary sewage in a wetland constructed for both treatment and wildlife habitat. Effluent concentrations were compared with surface and groundwater from a creek where recycled water was evaluated as a potential means to augment flow (Upper Silver and Coyote Creeks, San Jose, CA). In the recycled water, 90-470 ng/l perfluorochemicals were detected, predominantly perfluorooctanoate (PFOA; 10-190 ng/l) and perfluorooctanesulfonate (PFOS; 20-190 ng/l). No significant removal of perfluorochemicals was observed in the wetland (total concentration ranged 100-170ng/l across various treatment stages); in this case, 2-(N-ethylperfluorooctanesulfonamido) acetic acid (N-EtFOSAA), perfluorodecanesulfonate (PFDS), and PFOS were dominant. Though there is currently no wastewater discharge into the creeks, perfluorochemicals were found in the surface water and underlying groundwater at a total of 20-150 ng/l with PFOS and PFOA again making the largest contribution. With respect to ecotoxicological effects, perfluorochemical release via recycled water into sensitive ecosystems requires evaluation.

Economic and Ecological Costs and Benefits of Streamflow Augmentation Using Recycled Water in a California Coastal Stream

Streamflow augmentation has the potential to become an important application of recycled water in water scarce areas. We assessed the economic and ecological merits of a recycled water project that opted for an inland release of tertiary-treated recycled water in a small stream and wetland compared to an ocean outfall discharge. Costs for the status-quo scenario of discharging secondary-treated effluent to the ocean were compared to those of the implemented scenario of inland streamflow augmentation using recycled water. The benefits of the inland-discharge scenario were greater than the increase in associated costs by US

Near real-time N-nitrosodimethylamine monitoring in potable water reuse via online high-performance liquid chromatography-photochemical reaction-chemiluminescence

1.8M, with recreational value and scenic amenity generating the greatest value. We also compared physical habitat quality, water quality, and benthic macroinvertebrate community upstream and downstream of the recycled water discharge to estimate the effect of streamflow augmentation on the ecosystem. The physical-habitat quality was higher downstream of the discharge, although streamflow came in unnatural diurnal pulses. Water quality remained relatively unchanged with respect to dissolved oxygen, pH, and ammonia-nitrogen, although temperatures were elevated. Benthic macroinvertebrates were present in higher abundances, although the diversity was relatively low. A federally listed species, the California red-legged frog (Rana draytonii), was present. Our results may support decision-making for wastewater treatment alternatives and recycled water applications in Mediterranean climates.

An inline ion-exchange system in a chemiluminescence-based analyzer for direct analysis of N-nitrosamines in treated wastewater

Direct potable reuse requires stringent water quality assurance to protect public health. This study developed an online analytical technique—high-performance liquid chromatography followed by photochemical reaction and chemiluminescence detection (HPLC-PR-CL)—for determination of the concentration of N-nitrosodimethylamine (NDMA) and three other N-nitrosamines. Its feasibility for near real-time analysis was evaluated by analyzing an ultrafiltration (UF)-treated wastewater before and after a pilot-scale reverse osmosis (RO) treatment system. The online instrument with a method detection limit of 0.3–2.7 ng L−1 requires a direct injection (i.e., no sample pre-concentration) of only 20–200 μL sample volume for the determination of N-nitrosamine concentrations every 20 min. NDMA concentrations in UF-treated wastewater were successfully monitored in a range of 50–200 ng L−1 over the course of 24 h. Likewise, NDMA concentrations in RO permeate ranged from 26–81 ng L−1 over the course of 48 h. The online monitor was capable of recording variations in N-nitrosamine concentration in RO permeate that occurred following changes in feedwater concentration and temperature. This study demonstrates the potential for online water quality assurance via direct measurement of trace levels of organic contaminants, which is highly relevant to the implementation of potable reuse.

N-nitrosodimethylamine (NDMA) removal by reverse osmosis and UV treatment and analysis via LC–MS/MS

A newly developed, ion exchange-based inline pretreatment system was used to mitigate the effect of background constituents in natural water and treated wastewater to achieve rapid, reliable, and sensitive analysis of N-nitrosamines. The pretreatment system (anion exchange module, AEM) was incorporated into a high-performance liquid chromatograph (HPLC) coupled with a photochemical reactor (PR) and chemiluminescence (CL) detector (HPLC-PR-CL), which can analyze four hydrophilic N-nitrosamines at ng/L levels. This system requires no pre-concentration of the water sample nor the use of deuterated surrogates, unlike other conventional N-nitrosamine analytical techniques. The AEM converted anions in the eluent to hydroxide ions after HPLC separation and increased eluent pH, allowing for the subsequent photochemical reactions, which are otherwise achieved by pH conditioning with an additional dosing pump of basic chemical. The AEM also removed anionic interfering compounds (e.g. nitrate) from the samples, allowing for improved N-nitrosamine analysis in treated wastewater. The operating conditions of the AEM and PR were optimized to obtain sensitive and stable analytical performance. As a result, the lowest-concentration minimum reporting levels of N-nitrosodimethylamine, N-nitrosomorpholine, N-nitrosomethylethylamine, and N- nitrosopyrrolidine using the optimized system were 0.42, 0.54, 0.58, and 1.4 ng/L, respectively. The improved analytical method was validated by comparing the results with a conventional method based on gas chromatography coupled with a mass spectrometric ion trap detector. These results indicated that HPLC-PR-CL equipped with an inline AEM can be competitively applied as a rapid analytical technique for the determination of N-nitrosamines in various water matrices.