Ceramic nanofiltration-based treatment of NOM-rich ion exchange brine

Ion exchange (IEX) with anion resin can be used to remove natural organic matter (NOM) from drinking water sources. IEX resins require periodic regeneration, generating a waste brine stream rich in sodium, chloride, sulfate and NOM. This spent IEX brine is a pollutant and expensive to dispose, which hampers full-scale applications.

In this research, we proposed a spent IEX brine treatment that is based on ceramic nanofiltration and chemical precipitation. The treatment aims to recover a permeate of a reusable IEX regeneration salt solution, which is typically sodium chloride, by removing NOM and sulfate from the spent IEX brine. Also, concentrated NOM could be valuable due to the presence of humic substances.

First, the performance of IEX for NOM removal from surface water was explored using a case study on drinking water companies in the European North Sea region. Further, experiment in the laboratory and on site were performed to study the effect of ionic strength on NOM and sulfate removal by ceramic nanofiltration. Moreover, we investigated the interactions between the high concentrations of NOM and the chemicals during the precipitation of barite, gypsum and ettringite. Understanding these mechanisms could be a step towards the feasibility of the treatment and the disposal of the spent IEX brine and thus the application of IEX for NOM removal.