Combination of MIEX^® resin and ozonation for reduction of dissolved organic matter during aquifer recharge using municipal effluent

Abstract

Magnetic anion exchange resin treatment (MIEX^®), as well as ozonation, was applied as pretreatment for soil aquifer treatment (SAT). The removal of dissolved organic matter (DOM) derived from municipal effluent was characterized during these treatments. The DOM removal ratio increased with the increasing of MIEX^® resin dosage (5–20 mL/L), and a dosage of 5–10 mL/L was suggested for the SAT pretreatment. Under this dosage, 30 % DOC was removed from secondary effluent, which was much lower than those found with drinking water resources. The aromatic DOM with apparent molecular weight (AMW) ranging 2–5 kDa was preferentially removed by MIEX^®, especially for aromatic proteins. Differently, ozonation preferentially destroyed larger AMW (>10 kDa) DOM, especially for fulvic and humic acid-like materials. Better purifucation was achieved by combining the two technologies. With pretreatments (MIEX^®, ozonation, and combined MIEX^®/ozonation), the DOM removals by SAT were significantly improved. The DOC and UV₂₅₄ values were reduced by 40–77 % in SAT combined with pretreatments, compared with 20–30 % reduction by only SAT. Around 50% of the fluorescent DOM was reduced in SAT and MIEX/SAT systems, while higher reductions (76-84%) were achieved in ozonation/SAT and MIEX/Ozonation/SAT systems. Different modes were identified: ozonation improved SAT on removing DOM of 1.7–5.3 kDa, whereas MIEX^® treatment attributed to the removal of small AMW (0.5–1.7 kDa) DOM responsible for the absorbance peak at 300 nm. Based on the results, DOM removed by MIEX^® treatment is complementary with those removed by SAT and ozonation, and the best DOM purification was found in combined MIEX^®/ozonation/SAT.