water treatment

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.