Seawater-augmented potable reuse: simulating reverse osmosis treatment of integrated feedstreams

Water Reuse · 2026-04-10

ABSTRACT Conceptual diagram depicting key trends in closed-circuit reverse osmosis performance with seawater augmentation at potable reuse facilities, including system pressure and energy changes, permeate quality, and concentrate composition. Seawater-augmented potable reuse at an advanced water purification facility can provide additional water supplies without significant increases in infrastructure. Operational flexibility in the reverse osmosis (RO) process was conceptually analyzed using closed-circuit RO simulations. Feedwater-shortage and increased-production scenarios were compared with a baseline scenario with no seawater augmentation. Seawater augmentation increased the feedwater total dissolved solid (TDS) concentrations but diluted the wastewater constituents (organics and nutrients), and thus decreased the likelihood of RO membrane fouling. Maximum recovery rates, determined using pressure and solubility criteria, decreased from 90 in the baseline to 77% when blended with 30% seawater. The reduced recovery rates required increased RO feedwater flowrates and resulted in increased RO concentrate flowrates. With 30% seawater augmentation, the concentrate flowrate is ∼2.7 times higher, with a TDS ∼4.5 times higher than the baseline; this may require modifications to outfall infrastructure. On the other hand, nutrients in the concentrate to be discharged were diluted, which could reduce impacts on aquatic life and human health. Specific energy consumption increased from 1.36 in the baseline to 4.20 kWh/m3 with 30% seawater augmentation; however, low-pressure energy recovery devices can be implemented to mitigate energy penalties. Modifications to piping may also be required to increase corrosion resistance.

Role of wetting state in improved prediction of wetting resistance in membrane distillation

Separation and Purification Technology · 2026-01-10 · 1 citations

Membrane wetting remains a critical limitation in membrane distillation (MD), yet contact angle ( θ ) measurements that are commonly used to assess wetting resistance are defined and interpreted inconsistently in the MD literature. In this study, we characterize the surface properties and wetting resistance of three commercially available polytetrafluoroethylene membrane distillation (MD) membranes and clarify the physical meaning of commonly reported contact angles. By adapting an established method to quantify wetting-state transitions, we show that conventional contact angle measurements ( θ m , conv ) correspond to a Cassie-Baxter wetting state. We further demonstrate that the transition to a Wenzel wetting state occurs at applied pressures of ~270–290 Pa, well below typical MD operating pressures, indicating that these hydrophobic membranes operate in a Wenzel wetting state during MD. To more accurately characterize wetting resistance during MD, we introduce methods to calculate a pore-scale Wenzel state contact angle, θ W ∗ , based on measured membrane roughness and intrinsic contact angle ( θ 0 ). The resulting θ W ∗ values are unique: θ W ∗ is significantly greater (by 12–17%) than θ 0 and significantly less (by 11–17%) than θ m , conv . Importantly, the different definitions of contact angle lead to large discrepancies (20–185%) in predicted liquid entry pressure (LEP). Using electrochemical impedance spectroscopy to precisely measure LEP, we show that theoretical LEP values based on θ m , conv overestimate wetting resistance, while those based on θ 0 underestimate it. In contrast, LEP predictions based on θ W ∗ are in closest agreement with experimental measurements for all three membranes. This indicates that θ W ∗ best represents contact angles at pore entrances under MD operating conditions. This work provides new methods and physically meaningful metrics (i.e., θ W ∗ and theoretical LEP based on θ W ∗ ) for predicting wetting resistance, with direct implications for membrane design and operation.

Enhanced Cross-Sectional Imaging of the Selective Layer of Reverse Osmosis Membranes

Environmental Science & Technology Letters · 2026-01-30

The integrity and morphology of the selective layer of RO membranes significantly influence transport phenomena and membrane performance, motivating its cross-sectional imaging. Focused ion beam scanning electron microscopy (FIB-SEM) is a less complex technique for cross-sectional imaging that offers a broader field of view and a greater depth of focus, albeit with less resolution than transmission electron microscopy (TEM). In this study, we introduce and demonstrate a new surface-milling approach to improve the FIB-SEM imaging of RO membranes. We develop a bilayer conductive Pt coating topped with a protective carbon deposit; this approach avoids the need to cryo-fracture the membranes, which overcomes drawbacks associated with TEM and conventional FIB-SEM cross-sectional milling (e.g., curtaining and polymer melting). Applied to a commercial RO membrane, the method enabled robust quantification of key structural features and clear visualization of void spaces within the ridge-and-valley structure of the selective layer and pores in the uppermost portion of the support layer. The bilayer platinum coating enhances the delineation of the upper boundary of the selective layer, enabling rapid and accurate identification. With a field of view more than 20 times larger than TEM, FIB-SEM imaging captures a substantially greater cross-sectional area, yielding more representative measurements.

Advancing decentralized water reuse: pilot-scale testing of a membrane bioreactor – air gap membrane distillation system

Water Reuse · 2026-03-11

ABSTRACT Figure showing side of shipping container and a schematic of the treatment system Mobile water reuse units can be used in off-grid communities or conflict zones to provide sanitation and drinking water during times of need. In this study, a pilot-scale membrane bioreactor (MBR) – air gap membrane distillation (AGMD) system was installed in a CONEX shipping container, tested at one water reclamation facility, and subsequently transported to a second facility with different infrastructure and water quality. The MBR-AGMD treated approximately 1,000 L/day of municipal wastewater and consistently produced high-quality water with low total dissolved solids and only trace levels of organic contaminants. Non-volatile species were reduced by over 99% (2-log10). Total coliforms, Escherichia coli, somatic coliphages, and male-specific (F+) coliphages were reduced to levels below the limit of detection (1 Most Probable Number/100 mL) before reaching the MD system, representing reduction values of approximately 6-log10 and 5-log10 for bacteria and viruses, respectively. A co-spike test into the MD system was performed with >4-log10 removals for each virus tested. At the second site, pretreatment requirements were identified, as clogging from high levels of wastewater solids challenged the MBR unit. Additional components, including an external pre-filter tank, were added to increase flexibility for wastewater streams lacking treatment by screens or primary clarification.

The Future of Municipal Wastewater Reuse Concentrate Management: Drivers, Challenges, and Opportunities

UNC Libraries · 2026-04-15

Water reuse is rapidly becoming an integral feature of resilient water systems, where municipal wastewater undergoes advanced treatment, typically involving a sequence of ultrafiltration (UF), reverse osmosis (RO), and an advanced oxidation process (AOP). When RO is used, a concentrated waste stream is produced that is elevated in not only total dissolved solids but also metals, nutrients, and micropollutants that have passed through conventional wastewater treatment. Management of this RO concentrate─dubbed municipal wastewater reuse concentrate (MWRC)─will be critical to address, especially as water reuse practices become more widespread. Building on existing brine management practices, this review explores MWRC management options by identifying infrastructural needs and opportunities for multi-beneficial disposal. To safeguard environmental systems from the potential hazards of MWRC, disposal, monitoring, and regulatory techniques are discussed to promote the safety and affordability of implementing MWRC management. Furthermore, opportunities for resource recovery and valorization are differentiated, while economic techniques to revamp cost-benefit analysis for MWRC management are examined. The goal of this critical review is to create a common foundation for researchers, practitioners, and regulators by providing an interdisciplinary set of tools and frameworks to address the impending challenges and emerging opportunities of MWRC management.

Making waves: Conceptualization of seawater-augmented potable reuse

Water Research · 2025-08-29 · 1 citations

This study presents the novel concept of seawater-augmented potable reuse. Four treatment trains are conceptualized for indirect and direct potable reuse scenarios at a coastal potable water reuse facility. Treated wastewater is supplied by a wastewater reclamation facility with either a conventional activated sludge or membrane bioreactor process. Seawater from three intake types was integrated into the potable reuse facility such that existing advanced water purification processes were fully utilized without compromising potable water production. Seawater pretreatment requirements varied with raw seawater quality, seawater intake type, and existing treatment processes at the wastewater reclamation and potable reuse facilities. Seawater augmentation can provide additional water supply at coastal potable reuse facilities without significant increases in infrastructure. Supply and demand risks associated with independent seawater desalination and potable reuse projects can be reduced. Laboratory and pilot testing are required in further consideration of seawater-augmented potable reuse. Strengthened collaborations across water, wastewater, and desalination industry partners are also needed.

Chrome Plating Facility Siting Is Associated with Neighborhood Demographic and Socioeconomic Factors and Elevated Per- and Polyfluoroalkyl Substances in Blood in California

Environmental Science & Technology · 2025-06-16 · 2 citations

Chrome plating facilities release toxic chemicals, including perfluoroalkyl and polyfluoroalkyl substances (PFAS), disproportionately affecting nearby neighborhoods. We analyzed census-tract-level demographic and socioeconomic data using the American Community Survey (2018–2022) alongside 2019 data on chrome plating facilities from the California State Water Board. Two cohorts were included: adolescents from the Study of Latino Adolescents at Risk of Type 2 Diabetes (SOLAR; n = 238; recruited between 2001 and 2012) and young adults from the Metabolic and Asthma Incidence Research study (Meta-AIR; n = 118; 2014–2018). Plasma PFAS were measured via liquid chromatography–high-resolution mass spectrometry. Multiple linear regression assessed associations between neighborhood characteristics, numbers of chrome plating facilities, and PFAS concentrations in participants’ plasma. Compared to areas without chrome plating facilities, neighborhoods with one (or more than one) facility had 11% (22%) more Hispanic residents, 6% (9%) more residents without a high school education, and 3% (3%) more individuals below the poverty line. In Meta-AIR, residents within 3 km of these facilities were correlated with elevated plasma PFOS, PFHxS, and PFOA concentrations, and in SOLAR, with PFDA and PFHpS. Chrome plating facilities are concentrated in socioeconomically disadvantaged neighborhoods in California. Proximity to these facilities is linked to elevated blood PFAS levels.

Examining disparities in PFAS plasma concentrations: Impact of drinking water contamination, food access, proximity to industrial facilities and superfund sites

Environmental Research · 2024-11-14 · 16 citations

BACKGROUND: Most of the US population is exposed to per- and polyfluorinated substances (PFAS) through various environmental media and these sources of PFAS exposure coupled with disproportionate co-localization of PFAS-polluting facilities in under-resourced communities may exacerbate disparities in PFAS-associated health risks. METHOD: We leveraged two cohorts in Southern California with 8 PFAS concentrations measured in plasma. We obtained PFAS water testing data from the Third Unregulated Contaminant Monitoring Rule and state monitoring data, census tract-level information on food access using the Food Access Research Atlas, the location of Superfund sites on the National Priorities List, and data on facilities known to release PFAS pollutants. These data were then spatially linked to the participants' home addresses. RESULTS: In the first cohort, we found that detections of PFOS, PFOA, and PFHxS in drinking water were associated with 1.54 ng/mL (95% CI: 0.77, 2.32), 0.47 ng/mL (0.25, 0.68), and 1.16 ng/mL (0.62, 1.71) increase in plasma PFOS, PFOA, and PFHxS. The presence of Superfund sites was associated with higher plasma concentrations of PFOS, PFHxS, PFPeS, and PFHpS (betas [95% CIs]: 0.96 [0.21, 1.71], 0.9 [0.22, 1.58], 0.04 [0.02, 0.06] and 0.05 [0.02, 0.09], respectively). Each additional PFAS-polluting facility present in the neighborhood was associated with a 0.9 ng/mL (0.03, 0.15) increase in the concentration of PFOS. In the other cohort, we found that the presence of Superfund sites was associated with higher plasma PFDA, PFHpS, PFOS (betas [95% CIs]: 0.03 [0.01, 0.06], 0.05 [0.01, 0.09], and 1.96 [0.31, 3.62]). Neighborhood low access to food was associated with a 2.51 ng/mL (0.7, 4.31) increase in plasma PFOS, 0.6 ng/mL (0.16, 1.06) increase in plasma PFOA and 0.06 (0.02, 0.1) increase in plasma PFHpS. CONCLUSION: Reducing sources of PFAS exposure in under-resourced neighborhoods may help reduce disparities in human exposure levels.

Practical Minimum Energy Use of Seawater Reverse Osmosis

SSRN Electronic Journal · 2024-01-01

Onset, rate, and depth of wetting front progression in membrane distillation

Journal of Membrane Science · 2024-08-28 · 14 citations

In this study, electrochemical impedance spectroscopy (EIS) is used to characterize the onset, rate, and depth of wetting front progression in real time through commercial polytetrafluoroethylene (PTFE) membrane distillation (MD) membranes. Results showed that higher salinities, elevated transmembrane hydraulic pressures, and larger membrane pore sizes are associated with earlier onset, higher rates, and/or greater depths of wetting front progression – but, notably, in the absence of pore breakthrough. It was also shown that wetting is not an on/off switch; instead, membrane wetting resistance acts as a frictional force that can slow down or stop wetting front progression at different depths in the membrane. PTFE MD membranes were observed to often operate in a deeply wetted, but stable, transition state with normalized impedance values of ∼0.6 to ∼0.1, indicating mid-depth wetting, where the wetting front progresses into the bulk of the membrane and holds its position, or deep wetting, where the wetting front holds its position near the distillate-side surface of the membrane without pore breakthrough. Normalized impedance values as low as 0.04 held constant throughout a 14-day experiment in which pore breakthrough did not occur. These new impedance results strongly support the hypothesis that during MD, for saline feed solutions and under elevated transmembrane pressures – and especially for larger membrane pore sizes – the distillate-side surface can act as a final barrier to pore breakthrough. • Electrochemical impedance spectroscopy to measure wetting front progression in MD. • Stable mid-depth and deep transition wetting states exist in hydrophobic membranes. • Membranes can operate in a deeply wetted, stable transition state for 14 days. • Pore size, feed salinity, and pressure affect onset, rate, and depth of wetting. • Distillate-side surface acts as a final barrier to pore breakthrough.