COMPARING LOW PRESSURE MEMBRANE FILTRATION TO CONVENTIONAL TREATMENT FOR SURFACE WATERS

摘要

The favourable economics of organic membranes has led to their widespread application in hundreds of installations world-wide. The use of membranes in greenfield designs is commonplace, yet when considered for use in retrofit or other existing installations, membranes are often deemed too expensive.rnIn 2002, the Modesto Irrigation District set out on a program to expand their existing treatment works. The process, designed in the early 1990's, was state of the art at the time, consisting of pre-ozonation, flocculation/sedimentation, and deep-bed monomedia anthracite filtration. The process has worked effectively since start-up in late 1994, and treats a relatively high quality surface water (95th percentile turbidity < 20 NTU, TOC average 2.5 mg/L). California Department of Health Services (DHS) regulations require a high level of treatment due to upland cattle grazing and full body contact recreational use of the watersheds.rnThis paper discusses the criteria used to evaluate and select low pressure membranes to expand the Modesto Regional Water Treatment Plant.