Achieving no spent brine discharge in an anion exchange resin-based fixed-bed process for typical DOM removal

Abstract

The anion exchange resin (AER) process successfully removed dissolved organic matter (DOM) from various water matrices. To restore AER capacity by routine DOM removal from the regenerant is an attractive strategy to solve the spent brine disposal problem. This study investigated the long-term removal (from the feed) and accumulation (in the inorganic regenerant) characteristics of typical DOM molecules (including anionic pharmaceuticals, short-chain aliphatic acids, humic substances and amino acids) during ˜50 adsorption–regeneration cycles of an AER-based fixed-bed process with the routine physico-chemical purification treatment of the regenerant. All anionic DOM molecules complied with common long-term removal and accumulation mechanisms driven by both electrostatic and non-electrostatic interactions in a multicomponent system, regardless of aromatic structure, hydrophobicity/hydrophilicity, or water solubility. A high anionic DOM removal (˜90%) from the feed could be stably achieved after anionic DOM accumulated in the regenerant was effectively removed (˜80%) by more frequent regenerant-purification treatments. The AER presented here did not selectively remove aromatic and/or hydrophobic DOM molecules from water matrices during the long-term cyclic operation. These findings will enable the development of new designs of AER-based fixed-bed processes for DOM removal from various water matrices.