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Finished water hardness is not regulated,but many utilities target residual hardnesslevels at 50-100 mg/L as calcium carbonatein order to minimize such adverse effects asscale formation, deposition in hot waterpipes, and inhibition of the cleansing actionof soap and detergents. Operational datafrom a Florida utility that had implementeda full-scale magnetic ion exchange (MIEX)process upstream of its lime-softeningfacilities demonstrated improved calciumremoval after implementation of this treatment.However, the effects of natural organicmatter (NOM) in the lime-softening processwere not well understood. To bridge thisinformation gap, the authors undertook asystematic study of anion exchange removalof NOM and lime-softening.Analysis of simulated natural waters withvarying concentrations of dissolved organiccarbon (DOC) provided evidence that NOMinterferes with lime-softening by inhibitingcalcium carbonate nucleation and crystalgrowth. In this research, when model waterand real waters were pretreated with anionexchange resin, DOC concentrations werereduced and the result was improved calciumremoval by lime-softening. Includes 19 references, table, figures.

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Edition: Vol. 101 - No. 6 Published: 06/01/2009 Number of Pages: 10 File Size: 1 file , 690 KB