Comparison between magnetic ion exchange resin-ultrafiltration and enhanced coagulation–filtration for the treatment of an NOM loaded surface water

Abstract

The raw water of the waterworks in Kluizen contains high levels of NOM and alkalinity. The current treatment concept comprises enhanced coagulation followed by sludge blanket clarification, filtration, ozonation and Granular Activated Carbon filtration (GAC). A final disinfection with chlorine is applied. The enhanced coagulation, applied to achieve maximum NOM removal, requires a lot of chemicals and produces a lot of solid waste. In spite of this, the treated water still has a relatively high TOC content, resulting in a limited biostability. This disadvantage incited VMW to investigate an alternative treatment scheme consisting of magnetic ion exchange resin, ultrafiltration, ozonation, GAC filtration and chlorine disinfection. The alternative treatment scheme was operated over a two-year period in a pilot plant with a capacity of 50 m3/h, and its results with respect to water quality, chemical demand and operational costs were compared with those of the full-scale plant. The pilot treatment gives rise to an improved removal of NOM, which can be attributed mainly to the magnetic ion exchange resin process. This was shown to have a beneficial effect on both the biostability of the treated water and on the formation of disinfection by-products. The costs associated with the magnetic ion exchange resin process, which can be attributed mainly to resin loss and regeneration, are counterbalanced by cost savings due to lower chemical demand and solid waste formation.