COVER SERIES | Pottable Water
Control Disinfection
By-Products on Both Ends of the Treatment Train
Fluidized bed ion exchange and THM stripping work together to provide safer, cleaner water.
Russ Swerdfeger | Ixom Watercare
Disinfection by-products (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs), remain some of the most persistent compliance challenges in drinking water treatment. Formed when chlorine reacts with natural organic matter (NOM), they force utilities to balance microbial safety with long-term health risk and rising treatment costs.
The DBP Challenge: Health, Compliance & Cost
THMs and HAAs are regulated in drinking water because prolonged exposure to elevated levels of these DBPs has been associated with increased risks of certain cancers and reproductive and developmental effects. These compounds can form throughout the treatment and distribution process, so even trace concentrations can affect entire communities over decades, making prevention and control a critical public health responsibility.
The Environmental Protection Agency’s Stage 1 and Stage 2 DBP rules strictly limit THMs and HAAs. Traditional approaches, like optimizing chlorine dosing or relying solely on filtration, often fall short, especially in systems with high NOM or bromide concentrations. Treatment can also introduce financial burdens, as utilities may need to invest in additional steps or alternative disinfectants to consistently meet regulatory limits. Some approaches require higher chemical and energy use as well as increased monitoring and testing, driving both capital expenditures and long-term operating costs for potable water systems.
Fluidized Bed Ion Exchange: Targeting Precursors Before Disinfection
Fluidized bed ion exchange represents a shift in water treatment strategy by focusing on precursor removal early in the treatment train. Deployed ahead of disinfection, it targets natural organic matter by removing charged fractions of dissolved organic carbon (DOC), reducing the formation potential of disinfection by-products. This allows utilities to maintain effective disinfection while improving finished water quality and disinfectant stability.
In a fluidized bed contactor, ion exchange resin is continuously suspended, maximizing contact with the water and enabling efficient removal of organic precursors. Depending on source water and system design, DOC reductions of 40% to 60% are achievable. As this organic load is reduced, downstream processes operate more effectively. Coagulant and polymer demand can decline, sludge production from clarification is reduced and filtration systems can run longer between backwash cycles, improving throughput and operational consistency. In many cases, the need for pH adjustment associated with enhanced coagulation is also minimized.
Compared to conventional approaches that rely on increasing chemical doses, upstream ion exchange addresses the root cause of DBP formation rather than reacting to it. This can be a more stable and efficient treatment process with lower chemical use and reduced operational disruption. These systems are scalable and can be integrated into existing treatment trains or deployed in standalone configurations across a range of facility sizes.
As utilities expand treatment to address emerging contaminants such as per- and polyfluoroalkyl substances (PFAS), upstream removal of competing organic matter becomes even more important. By reducing fouling and competition for adsorption sites, ion exchange improves the performance and lifespan of downstream media such as granular activated carbon, extending changeout intervals and enabling more practical reactivation strategies.
The result is a more resilient and cost-effective treatment approach that reduces chemical demand, waste generation and long-term operating expenses while improving overall system performance.
| IMAGE 1: Example fluidized bed ion exchange flow schematic (Images courtesy of Ixom Watercare)
THM Stripping: Managing Volatile DBPs After Formation
While upstream control of DBP precursors is an effective strategy, many systems still experience THM formation within storage and distribution networks. In these cases, THM stripping provides a practical downstream solution to manage concentrations and maintain compliance.
Air-stripping aeration is a widely used approach, operating on the principles of Henry’s Law to transfer volatile THMs from water into the vapor phase. By maximizing contact between air and water, these systems can effectively reduce THM levels without significantly impacting chlorine residuals. This makes them particularly well suited for storage tanks and reservoirs, where THMs tend to accumulate over time.
For more localized challenges, such as THM hotspots within specific areas of a distribution system, spray aeration offers a targeted option. By dispersing water into fine droplets, it increases surface area and promotes rapid volatilization. This approach can often be retrofitted into existing infrastructure with minimal disruption.
In systems where storage-based treatment is not feasible, in-line aeration units provide a compact alternative. Installed directly within the pipeline, these systems treat water in real time, enabling THM reduction without major structural modifications.
| IMAGE 2: Typical in-line spray aeration for THM removal
Integrated Strategy: Combining Upstream & Downstream Solutions
The most effective DBP control strategies combine both approaches. Upstream ion exchange reduces the formation potential, while downstream THM stripping manages what cannot be prevented. Together, they create a more reliable and controllable compliance framework than either approach alone.
Utilities benefit from this integrated strategy by achieving consistent compliance with Stage 2 DBP regulations, even under challenging source water conditions. Water quality improves across multiple dimensions, including taste, odor and safety, while chemical usage and energy consumption are reduced. Maintenance demands are also lowered thanks to the reduced burden on downstream filtration and disinfection infrastructure. Ultimately, this dual-layered approach supports both short-term performance goals and long-term sustainability.
Modern DBP control demands a multipronged strategy. Upstream ion exchange tackles the root cause—precursors—while THM stripping removes residual contaminants. Together, these technologies offer a scalable and cost-effective path to safer, cleaner water. As regulatory pressures mount and public health concerns grow, utilities can embrace these innovations not just as compliance tools for today, but as cornerstones of intelligent and future-ready water management.
Russ Swerdfeger is the head of marketing and strategy at Ixom Watercare. For more information, visit ixomwatercare.com.
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