AWWA WQTC60658

This paper presents the results of an extended series of pilot testing designed to use existing and novel methods to control bromate formation at the Colored Water Treatment Facility (CWTF). Based on previous work performed by other water utilities, information in the scientific literature, and some earlier pilot testing performed by McGuire Environmental Consultants, Inc. (MEC) on a similar raw water quality, a pilot plant was designed and constructed at the CWTF. The goal of the pilot testing was to simultaneously produce treated water that would meet Mesa's color target of 7 to 8 color units (PCU) and the Stage 1 Disinfectant/Disinfection Byproduct (D/DBP) Rule Maximum Contaminant Level (MCL) of 10 mg/L. The pilot plant was used to test various combinations of allowable drinking water treatment chemicals and their effect on bromate formation for the challenging raw water quality found at the CWTF. When it became clear that the target water quality could not be reliably achieved using chemical pretreatment alone, an additional treatment process (MIEX, or Magnetic Ion EXchange) was tested. MIEX treatment had been previously shown to be highly effective at color removal, and it was hypothesized that increased color removal would result in lower ozone doses and reductions in bromate formation. Finally, when this configuration was found to be insufficient for meeting both color and bromate targets, the order of treatment was switched, and the MIEX treatment process was used as a polishing step to remove color that was not previously removed by ozone treatment. Includes tables, figures.