water treatment

This NAWI-funded led by Texas A&M University, focused on improving potable water reuse by developing an electrocoagulation/electrooxidation (EC/EO) treatment process for secondary-treated municipal wastewater. The project aimed to create a more streamlined and cost-effective treatment train capable of meeting strict public health requirements for controlling viruses while also reducing membrane fouling and reliance on hazardous treatment chemicals.

Currently, the “gold standard” potable reuse system involves multiple treatment stages, including microfiltration/ultrafiltration, reverse osmosis, advanced oxidation, and disinfection and occasionally conventional coagulation for pretreatment. Traditional coagulation approaches involves transporting, storing, and handling corrosive chemicals. The project investigated iron-based electrocoagulation as an additional pretreatment alternative wherein a sacrificial iron anode released coagulant precursors directly into the water through electrochemical reactions, nearly eliminating the need for chemical dosing. Researchers further hypothesized that pairing electrocoagulation with electrooxidation can simultaneously remove viruses through coagulation and inactivate them through oxidative reactions.

The research team evaluated both iron-iron (Fe-Fe) and iron-carbon (Fe-C) electrode systems using batch and flow-through reactors designed to mimic municipal secondary wastewater effluent conditions. Key objectives included increasing virus mitigation, enhancing ultrafiltration productivity, reducing long-term electrode fouling/passivation, and performing technoeconomic analysis. The Fe-C EC/EO configuration showed the strongest performance. According to the project findings, the Fe-C system outperformed both Fe-Fe electrocoagulation and conventional ferric chloride coagulation by more than two orders of magnitude or two virus log reduction values (LRVs). At pH 6.5 and an iron dose of 20 mg/L, the Fe-C system achieved greater than 3-log virus reduction in under five minutes, while Fe-Fe systems required approximately ten minutes. Flow-through testing demonstrated that LRVs greater than 4 were achievable after about 20 minutes of flocculation.

The enhanced virus control appears to result from combined physical removal and oxidative inactivation mechanisms. Researchers identified electro-Fenton chemistry as an important contributor, with the Fe-C system producing hydrogen peroxide and reduced iron i.e., Fe(II), which generate reactive oxidative species capable of inactivating viruses. The project also developed electrochemical and kinetic models that successfully predicted concentrations of Fe(II), total iron, dissolved oxygen, and hydrogen peroxide during operation.

Another important aspect of the project was membrane pretreatment. Electrocoagulation pretreatment significantly reduced ultrafiltration fouling, particularly at pH 6.5, where large iron flocs improved water quality and ultrafilter performance. The team also addressed operational durability by using polarity reversal to reduce electrode passivation. Reversing electrode polarity helped dislodge fouling layers, restore operational voltage, improve Faradaic efficiency, and decrease energy consumption during long-term operation.

The project included collaborations among Texas A&M University, Oak Ridge National Laboratory, Lawrence Berkeley National Laboratory, Orange County Water District, WaterTectonics, and other industry and research partners. Advanced characterization tools such as electron microscopy, neutron scattering, matrix assisted laser desorption ionization-time-of-flight mass spectrometry, and X-ray spectrometry supported the research, while technoeconomic analysis evaluated the feasibility of up-scaling the technology. Preliminary analysis suggested that EC/EO systems may reduce capital costs (CAPEX), although operational costs (OPEX) could increase.

Overall, the project demonstrated that iron-based EC/EO systems are promising alternatives to conventional coagulation and can increase virus LRVs during potable reuse applications. If successfully optimized at scale, these modular and electrified treatment systems could lower pretreatment costs, improve system resiliency, reduce hazardous chemical use, and support broader adoption of potable water reuse technologies.

Inland brackish groundwater desalination has the potential to expand water supplies in water-scarce areas, but adoption is constrained by the high costs and environmental impacts of concentrate (brine) disposal. Brine valorization—selectively extracting marketable products from desalination brines—offers a pathway to offset disposal costs, reduce environmental impacts, and improve economic feasibility. The challenge is that market potential depends both on technical recoverability of constituents and the ability of local or regional markets to absorb them.

To combat this challenge, a team of NAWI researchers, led by Alison Fritz at the National Energy Technology Laboratory (NETL), along with Alexander Dudchenko (SLAC), Casey De Finnda (UC Davis), and Meagan Mauter (Stanford), focused on two objectives. First, to develop a geospatially resolved market assessment that identified existing and potential markets for bulk constituents by pairing brine composition and expected volumes with market data on building materials, fertilizer, road salts, and chemicals, including caustic soda and hydrochloric acid. Second, to conceptualize and develop process models for brackish groundwater treatment and valorization and perform an economic and life cycle assessment of the proposed treatment.

To achieve the first goal, the project team used the U.S. Geological Survey brackish water databases to quantify volume and composition of groundwater sources across the United States. By pairing this volume and composition data with regional market demand for building materials, fertilizers, road salts, and industrial chemicals, the team conducted mass balances to determine how much recovered material local markets could realistically absorb. Next, to model the performance and costs of these prospective systems, they used NAWI’s WaterTAP platform to construct a digital reference treatment train. They then built a superstructure optimization model capable of evaluating the costs of thousands of candidate process configurations for treatment and valorization.

The preliminary optimization results indicate that in most scenarios, byproduct valorization is not the economically optimal configuration. The costs of the extraction schemes can outweigh the low market value of the recovered commodities. However, for certain water chemistries it can be valuable. For example, in highly saline scenarios, generating sodium chloride for road salt and hydrochloric acid and sodium hydroxide yielded outcomes that reduced net water treatment costs. The project also learned through stakeholder engagement that adaptable technologies that allow valorization decisions to follow market trends can improve the economics in volatile product markets.

Read the project brief and check out the project poster to learn more. To learn more about WaterTAP, register for NAWI’s upcoming webinar.

Conventional scale mitigation methods—anti-scalant addition, ion-exchange resins, and solvent extraction—require significant chemical or thermal inputs, which complicate brine management. While electrodialysis (ED) can potentially separate mono- and divalent ions, current membranes lack the selectivity needed for effective scaling control.

This project, led by Jovan Kamcev at the University of Michigan with partners at Lawrence Berkeley National Laboratory and Veolia WTS, focuses on developing highly selective ion-exchange membranes to improve ED pretreatment for brackish water reverse osmosis (BWRO). The developed membranes could enable high-recovery BWRO processes that are chemical-free and energy-efficient, improving brackish water desalination sustainability and reducing concentrate management challenges.

These membranes were tested in bench-scale ED systems to determine their ability to reduce scaling potential in RO processes. Process modeling was employed to optimize operational parameters, including water recovery and energy consumption, for maximum efficiency.

Testing revealed that divalent-selective single-layer membranes achieved Ca²⁺/Na⁺ selectivity values of approximately 4 at low current densities, a performance level notably higher than that of commercial membranes. Monovalent-selective bilayer membranes exhibited extremely high Na⁺/Ca²⁺ selectivity across various brackish water chemistries; however, their ion transport fluxes were about an order of magnitude lower, reflecting the reduced limiting current density inherent to the design. Membranes featuring sulfonate and phosphate functional groups demonstrated the best Ca/Na separation factors under realistic brackish water compositions, indicating strong potential for practical scaling control.

Following bench-scale validation, the membranes will be scaled up for pilot plant demonstrations in collaboration with an industrial partner. A technoeconomic analysis will also be conducted to evaluate the commercial viability and overall feasibility of these pretreatment solutions.

The next phase will focus on conducting ED experiments using larger membrane stacks, with findings intended to calibrate the ED process model developed by WaterTAP. This progression marks a significant step toward bridging bench-scale insights with pilot-scale application readiness.

Access the project poster for more information.

Current reverse osmosis and nanofiltration membranes, which are often extremely delicate and thin, generally do not tolerate waters with suspended solids or high loadings of organics. Pretreatment is nearly always employed to reduce these contaminants which can foul or even abrade membranes. Current pretreatment approaches rely on decades-old technology, are expensive or chemically intensive, and can constitute a majority of the system footprint. They are also difficult to adapt for different treatment systems and typically struggle to entirely prevent fouling.

NAWI’s 5.22 project, “Printed Polyelectrolyte Complex (APEC) Membranes for Ultra-high Permeance Nanofiltration,” aims to create the first nanofiltration (NF) membranes for universal pretreatment. These NF membranes would streamline the pretreatment process to be more efficient across different types of treatment systems or water sources while simultaneously saving costs, energy, and treating more water with better output quality.

This project achieve this using a newly developed additive manufacturing process. This process, known as electrospray, which uses high voltage to induce fine, nano-scale sprays to deposit thin and defect-free layers of polymer electrolyte and produce multi-layered membranes with better control. This technique, called “electrospray additive manufacturing,” can form exceptionally thin (~10s of nanometers per layer or less) and defect-free films from any solution-processable polymer.

Electrospray is suited for forming amphiphilic polyelectrolyte complexes (APECs), which bring the positively and negatively charged polymers together to form a material that is both hydrophilic and hydrophobic. These specific properties of APECs create a stronger, adjustable material that better prevents fouling. By using numerous yet exceedingly thin bilayers, the goal of the research is to prevent membrane defects and make pretreatment more efficient, while creating NF membranes with the potential for 5-10 times higher permeance than commercial NF membranes made today.

NAWI has funded a number of pilot projects that are intended to demonstrate the scaling of new technologies from bench scale or laboratory prototypes to large—and often mobile—field-deployed systems on relevant waters at or near their source. One such pilot project, led by Purdue University, is looking at batch reverse osmosis (BRO).

BRO has been proposed as a more energy-efficient alternative to conventional reverse osmosis (RO), primarily due to the former’s ability to operate closer to the brine’s osmotic pressure during permeate production. In this work, David Warsinger and his team designed, constructed, and tested a pilot-scale conventional RO, closed-circuit RO (CCRO), double-acting reciprocating piston BRO, and bladder-based BRO configurations within the combined system. By using the same pilot system across all tests, the influence of variables such as feed water composition, membrane type, piping, and pump selection is minimized. The pilot system is fully operational and can automatically run using a LabView VI.

The system is designed to handle high-salinity water and is comprised of several components (e.g., check valves, 3-way valves, and 2-way valves). A 5-micron cartridge filter was installed to protect the RO membrane and remove small particles. A feed tank provides the necessary feed water to the system, while separate tanks are used to store the brine and permeate flows. Additionally, different sensors and transducers are used to monitor the main operational variables in the system such as flow rates, pressure, conductivity, pH and temperature.

Experimental results obtained with the pilot system were used to parameterize and validate a predictive model. This model discretizes the membrane module’s feed channel in both the axial and transverse directions to capture the effects of concentration polarization and pressure losses on system performance. By simulating the pressure evolution over time, this model can calculate the system’s specific energy consumption (SEC).

The system has operated continuously for over 900 hours, with seamless switching between configurations. To date, more than 800 million data points have been collected.

The pilot has been operated with different feed salinities (brackish and seawater) and a range of water fluxes and recovery ratios. Preliminary results support previous predictions, showing that CCRO and Batch RO outperform Conventional RO in energy efficiency and achievable recovery.

The results also show that the selected performance indicators are being met with minimal to no leaks observed at operating pressures of up to 1000 psi. Both SEC and the recovery ratio remained within 5% of initial values throughout testing, even after consecutive operating cycles.

For more information, access the project research brief.

A recent article in the Chemical Engineering Journal details a study of how electromagnetic field (EMF) technology can reduce mineral scaling in water treatment systems and why results vary across applications. Mineral deposits such as calcium carbonate, gypsum, and silica—often called scale—can coat pipes, heat exchangers, and membranes, reducing efficiency, blocking flow, and increasing maintenance and cleaning demands. Conventional chemical antiscalants can be effective but raise concerns about handling, cost, waste, and the long-term complexity of continuous dosing and system monitoring.

The study by NAWI researchers Pei Xu, Xuewei Du, Huiyao Wang, Yanxing Wang, Fangjun Shu, Lawrence Anovitz, Ke Yuan, and others, shows that EMF treatment can reduce scaling by influencing both minerals suspended in water and crystals growing on surfaces. Bench tests on heat-exchanger and membrane-distillation systems showed fouling dropped by 15–79%, while pilot and field studies in reverse osmosis systems saw scaling fall by 40–45%. EMF effectiveness is highly dependent on water chemistry, system configuration, and operating conditions, which helps explain why some systems see strong results and others see less benefit.

EMF works through two main mechanisms: homogeneous nucleation in the bulk solution and heterogeneous crystal growth on surfaces. The study also explores how EMF strength, frequency, waveform, and flow velocity affect outcomes. By combining pilot-scale experiments and modeling simulations, the study shows how adjusting these parameters can optimize performance for different water treatment setups.

EMF systems operate without chemicals, produce no secondary waste, and require minimal energy. Case studies in cooling towers and reverse osmosis systems show reduced cleaning downtime, energy savings, and longer water reuse before blowdown or discharge. The study notes that hybrid approaches, combining EMF with low-dose antiscalants, may further improve reliability and cost-effectiveness, but systematic testing is needed to confirm performance and compatibility.

The authors conclude that EMF shows real potential for chemical-free scale control, but its effectiveness depends on a clear understanding of how it affects mineral behavior in water and how deposits attach to surfaces. Although long-term, full-scale validation and standardized testing protocols are still needed, the study sheds light on the mechanisms and operational factors that drive performance. By clarifying how EMF interacts with different water chemistries and system conditions, the study highlights the circumstances under which EMF could provide a reliable, cost-effective approach to reducing mineral scaling in a range of water systems.

Per- and polyfluoroalkyl substances (PFAS)—often called “forever chemicals”—are among the most stubborn contaminants found in drinking water today. Designed to resist heat, water, and degradation, these synthetic compounds persist in the environment and accumulate in the human body, making them notoriously difficult to remove using conventional treatment methods.

In a new study, researchers from the University of California Berkeley, the Colorado School of Mines, and Konkuk University in Seoul, and report a promising new approach: a family of porous polymer materials designed to rapidly and efficiently capture PFAS from water.

Rather than relying on a single material, the team developed a library of sponge-like adsorbents, each engineered with distinct chemical features intended to attract PFAS molecules. As contaminated water flows through the adsorbents, PFAS compounds bind to the material while clean water passes through. Testing the materials side by side allowed the researchers to directly compare how different chemical interactions embedded within the materials influence PFAS capture under realistic water conditions.

One clear trend emerged. Materials containing a positive charge were especially effective at drawing PFAS molecules in, highlighting electrostatic attraction as a key design principle for future PFAS adsorbents. Among the materials tested, one stood out for its performance—though the researchers emphasize that effectiveness alone is not enough.

The study also addresses a critical, and often overlooked, question in PFAS remediation: what happens after PFAS are removed from water? Captured PFAS must still be managed safely to avoid simply shifting contamination from one place to another. The researchers explore strategies for concentrating recovered PFAS so they can be more efficiently destroyed using emerging treatment technologies.

By considering adsorption and material regeneration together, this work underscores the importance of PFAS treatment solutions that function across the entire treatment lifecycle. Beyond demonstrating strong performance, the study provides practical design guidance for developing next-generation materials that are safer, more effective, and better suited for real-world water treatment systems.

As communities continue to grapple with widespread PFAS contamination, this research represents an important step toward technologies capable of addressing not just the presence of PFAS—but the full challenge of removing and ultimately eliminating them from water supplies.