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.