Segmented regeneration of ion exchange resins used for natural organic matter removal

• Sulfate desorbed at a lower brine concentration with a faster rate than NOM. • Segmented regeneration can reduce salt usage and improve the brine use efficiency. • Sulfate and NOM can be selectively recovered using segmented regeneration. • The volume ratio of 3:0.8 was the optimal condition for segmented regeneration. This study investigated the feasibility of using segmented regeneration for ion exchange (IX) resins used for natural organic matter (NOM) removal. For the first part of the study, regeneration batch tests were conducted for resins solely loaded with sulfate (i.e. Resin Sulfate ) or NOM (i.e. Resin NOM ). We found that Resin Sulfate can be fully regenerated using a lower brine concentration (40 g NaCl/L vs 100 g NaCl/L) with a much faster desorption rate compared to Resin NOM (time to reach equilibrium: < 3 min vs approximately 60 min). For the second part of the study, resins recovered from a pilot plant were regenerated in bench-scale columns using conventional (2 bed volume (BV) of 80 g NaCl/L) and segmented regeneration strategies (10 g NaCl/L followed by 120 g NaCl/L), and different volumetric ratios between low-concentration brine and high-concentration brine were assessed for segmented regeneration. It was determined that the optimal segmented regeneration, which uses 3 BV of low-concentration brine followed by 0.8 BV of high-concentration brine, achieved an equivalent regeneration efficiency (77%) to conventional regeneration while reducing salt usage by 21% and improving the brine use efficiency from 16% to 21%.