New options for achieving regulatory compliance with low-pressure membranes

Abstract

Protection against chlorine resistant pathogens, and Cryptosporidium in particular, has become a critical issue for water purveyors. For plant retrofits, ozone and more recently ultraviolet (UV) light technologies, are considered cost-effective solutions to provide an additional barrier to pathogens. The membrane filtration technology is, however, rapidly evolving and both costs and system recoveries are consistently improving. By physically removing microorganisms membrane filtration avoids the formation of disinfection by-products (DBPs) and the need to address changing target pathogens. This paper will present data collected using a novel pilot which evaluates the custom design approach and allows multiple types of membrane modules to be evaluated within a single pilot unit. Pilot testing was performed at the Marden Water Treatment Plant, in Sheboygan, North Shore, and Green Bay, Wisconsin, during 2000 and 2001. An analysis, based on data generated during these pilot tests, will be presented that shows that granular media filter boxes can be rehabilitated with membrane filtration and increase filtration capacity by at least 15%. This engineering analysis includes evaluation of specific aspects of the process including filtration mode, flux, backwashing, the layout of the existing facilities, the potential to reuse existing equipment, and cost comparisons with proprietary membrane systems.