An Evaluation of Magnetic Ion Exchange (MIEX®) for NOM Removal

A new process for the removal of natural organic matter (NOM) was developed in Australia by Orica Watercare and South Australian Water Corporation. It employs a strongly basic anion exchange resin to remove NOM from water. In the first stage of the process, the (180 μm) MIEX® resin is mixed with the water to be treated and its small size encourages rapid removal of NOM. The resin beads also contain a magnetic component responsible for their rapid agglomeration and very efficient removal by sedimentation in the second stage of the process. A continuous process is achieved by recycling approximately 90% of the recovered resin and adding the remaining 10%, required for maintaining the resin concentration, as fresh (regenerated) resin. The remaining 10% of the recovered used resin is sent to a regeneration system where it is regenerated with 2M NaCl.

The MIEX® process was evaluated to determine how it might be best implemented for NOM removal and DBP reduction at the Saint Paul Regional Water Services (SPRWS). Batch and pilot plant studies were conducted to evaluate the MIEX® resin performance when it was applied before and after the lime softening. Measurements of TOC and ultraviolet absorbance (UVA) were made to characterize NOM removal. In addition, the impact of the MIEX® treatment on the chemical requirements for softening, and the DBP formation potential of the treated water, were also evaluated.

This paper provides an assessment of the MIEX® treatment process for NOM removal. Data on process performance, the impact of operating conditions, point of application, dosage, regeneration conditions etc., are presented and discussed.

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