Membrane processes often are thought to be associated with high costs, but the Jamestown Water Treatment Plant (WTP) project demonstrates that assumptions do not always yield truth.
“One of the stereotypes associated with membrane filtration is that the capital costs for these facilities usually can be prohibitive,” said R. Vaughn Williams, P.E., project manager, Kenvirons Inc. “By reusing a lot of the old basins or existing basins at Jamestown, we really can focus the majority of the construction toward the membrane filtration facilities, and we really did that in an economical way.” A unique feature of the Jamestown WTP project developed from the urgent need for more potable water. The existing WTP was already experiencing peak demands in excess of its rated capacity when the packaged plant was mobilized at the site. The interim plant provided several benefits: additional water for high-demand periods, training for the city’s operators and optimized operation of the membrane filters. The membrane filters used in the package plant were relocated into the permanent plant. Economic conversion of a conventional treatment plant into a modern membrane filtration plant necessitated creative modifications of the existing facilities. The conventional plant had three independent flocculation/sedimentation trains, and each was modified for inclusion into the new treatment strategy. Basin No. 1 is now used to recover 90% of the waste stream generated by the membrane filters, Basin No. 2 is used for pretreatment and Basin No. 3 is divided into two independent three-stage flocculation basins. “We switched from a conventional treatment process to a membrane filtration process, which has a much smaller footprint, and we reuse the old basins for other functions,” Williams said. “We converted flocculation basins, converted the old filters and chemical storage areas. One of the said basins was converted into a reject recovery basin. So instead of wasting the reject water coming off the membranes, we took a tenth of it, which is about 10% of the total flow coming into the plant.” “We’re taking that flow, reducing it back down by another 10%, so we’re only wasting a very small percentage of the water coming up the hill into the water plant.”