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The main objective of this research was to determine the integrity of reverse osmosis (RO) and nanofiltration (NF) membranesystems with respect to microbial passage using both microbial- and non-microbial surrogates.The focus of this paper is to present the results from pilot-scale tests. Pilot-scale experiments were conducted at two sites: Water Factory 21 (WF-21) at theOrange County Water District (OCWD) in Fountain Valley, Califormia and the Northwest River WaterTreatment Plant (NWR-WTP) in the City of Chesapeake, Virginia. The source waters used weremicro-filtered secondary effluent (MFSE) for the WF-21 tests, and conventional process-treatedriver water (CTRW) for the NWR-WTP tests. Waters from WF-21 and NWR-WTP wereselected to reflect two generic types of source waters, i.e., surface waters and reclaimedwastewater effluent, for which disinfection or removal credit for pathogens by RO and NF wouldbe most likely required.Two units were employed for testing in WF-21: a dual-element test unit (DETU) and a multi-stage test unit (MSTU). The DETU consisted of two pressure vesselsarranged in series, operated in single-pass mode with no concentrate or permeate recycle to thefeed. The ESPA1 RO element was operated in the lead vessel and the TFCS NF element in thetrailing vessel. The test surrogates were injected into the feed line using an electromagneticdosing pump. Pressure was measured in the feed and concentrate of each vessel using a singlepressure gauge coupled to a 4-way selector valve. Permeate flow rate in each vessel and the finalconcentrate flow rate were measured using in-line flowmeters. Samples were collected from thefeed (from an in-line sample port), the permeate from each vessel, and the final concentrate. TheMSTU setup consisted of two separate flow streams in parallel each with two vessels in series(i.e. four lead vessels) followed by combined flow with a series of two vessels in series. Each vessel was designed to hold three spiral-wound elements. Permeate flows wereregulated by a valve located in the final concentrate line. Permeate and concentrate flow rateswere measured using in-line flowmeters. A single pressure gauge coupled to a four-way selectorvalve was used to measure the pressure difference between feed and concentrate at differentlocations (i.e., vessel 1

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Edition: Vol. - No. Published: 06/16/2002 Number of Pages: 14File Size: 1 file , 420 KB