Electrochemical regeneration of macroporous anion exchange membrane Adsorbers for the removal of natural organic matter (NOM)

The removal of Natural Organic Matter (NOM), a major precursor to potentially toxic disinfection by-products, is a challenge in water treatment. Porous anion-exchange (AEX) membrane adsorbers (MAs) combine convective transport and selective adsorption, offering a promising approach. However, conventional AEX regeneration relies on chemical treatments that generate secondary waste. This study presents a sustainable, chemical-free regeneration method using localized electrochemical pH modulation via the oxygen reduction reaction (ORR) at a graphite felt electrode near planar MAs. Electrochemical analysis identified an optimal potential window (+100 to −1000 mV vs. Ag/AgCl), enabling localized alkalinization with minimal hydrogen evolution. Regeneration efficiencies ranged from 20 to 60% for groundwater (GW), surface water (SW), and model NOM compounds under standard conditions, with highest values observed for GW and SW. A flux of 100 LMH ensured best mass transport for oxygen during ORR, and higher pH promoted alkaline deprotonation of weak basic AEX, enhancing regeneration. Under optimized conditions with elevated pH 10 efficiencies reached up to 77 ± 6% regeneration of UV 254 active NOM and 85 ± 4% TOC, respectively. Cyclic operation was successful despite mainly initial irreversible fouling and minor loss thereafter. This electrochemical approach has the potential to extend MA lifespan and postpone disposal or chemical regeneration. The additional energy requirement is low, at 0.02 kWh per m 3 treated water. Overall, this chemical-free, energy-efficient method represents a potentially more sustainable NOM removal via AEX MAs. • Electrochemical regeneration uses external electrodes near anion exchange membrane adsorbers to modulate local pH. • Oxygen reduction reaction induces localized alkalinity, enabling regeneration of weak base anion exchange membranes. • Regeneration efficiency depends on feedwater pH, flow rate, and applied cathodic potential. • Regeneration efficiencies up to 77% (UV 254 ) and 85% (TOC) were achieved under optimized conditions. • Multiple reuse cycles with low additional energy consumption and extended membrane adsorber lifespan.