The MIEX® DOC Process was developed specifically for the removal of problematic natural organic matter (NOM) in drinking water production. The Mt Pleasant plant in South Australia was constructed to assess the MIEX® DOC Process in likely operating scenarios including retrofit into existing conventional water treatment plants and installation into new plants combined with microfiltration. The plant has been operating since 2001. In conjunction with this has been an extensive laboratory investigation into the factors impacting on the effectiveness of the process for dissolved organic carbon (DOC) removal and water quality improvement, particularly for MIEX® treatment combined with coagulation. Both plant monitoring and laboratory studies indicate that changes in the character of the NOM and water quality have had a significant impact on DOC removal by the MIEX® resin. MIEX® and coagulation have been very effective in combination and consistently reduced turbidity to <0.5 NTU from an average of 60 NTU. The target is now to achieve higher DOC removal rates. To achieve this, it is important that the influence of water quality changes on the MIEX® and coagulation processes, particularly the impact of changes in NOM character are fully understood.