AWWA WQTC60681

Raw water sources for the Palmdale Water District (District) include State Project Water (SPW) and Littlerock Reservoir, which are treated at the Palmdale Water Treatment Plant (WTP), and also several groundwater wells. The District has struggled to comply with Stage 1 of the Disinfectants and Disinfection Byproducts Rule (D/DBPR), which includes stringent limits on chlorination byproducts, in particular total trihalomethanes (TTHMs) and five haloacetic acids (HAA-5). The main reasons for the elevated levels of TTHMs and HAA-5 are the nature and amount of natural organic matter (NOM) and the presence of significant concentrations of bromide in SPW. The District has taken steps to reduce disinfection byproduct (DBP) levels within the distribution system, such as increasing the use of groundwater (and decreasing the use of SPW) and increasing coagulant doses. Neither of these strategies is a sufficient long term solution. The District is performing a pilot study to evaluate combinations of processes to improve DBP control at the plant and to achieve compliance with the Stage 1 and 2 D/DBPRs. Process operating conditions, design criteria and, preliminary costs were developed in a previous desk-top level study, for MIEX®, granular activated carbon (GAC), fixed bed ion exchange (IX), and high-pressure membranes. That study formed the basis for selection of initial operating conditions for this pilot study. Process combination for THM precursor removal, included in the pilot study are: MIEX® (magnetically impregnated ion exchange resin) with enhanced coagulation and downstream GAC treatment; MIEX® in combination with a novel ceramic membrane; and, Fixed-bed IX with conventional treatment. GAC treatment was also investigated for removal of THMs formed in the upstream processes. Plant operations data indicates that bromide is largely incorporated into THMs within the treatment train. Adsorption of those THMs would mean that the GAC was essentially functioning as a bromide removal process. This paper presents preliminary results for the MIEX®/conventional treatment combination. Tentative conclusions are provided, based on an analysis of the pilot data collected to date, and the results of the previous desk-top study. Includes tables, figures.