Water. desalination + reuse

May/June 2013

Water. Desalination + reuse

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Page 36 of 51

TECHNOLOGY New Dow factory meets growing particle filter demand _________ Dow Water & Process Solutions ___ CASE STUDIES The following case studies illustrate its use as pretreatment prior to membrane treatment. ALTErNATIvE TO DAF FOr UF PrETrEATmENT Ultrafiltration UV Light Bear Valley Water District, California The Bear Valley Water District (BVWD) in Alpine, California, USA, serves approximately 500 residents and a variety of resorts, taking care to maintain a pristine mountain environment. In 2005, it was issued a National Pollutant Discharge Elimination System (NPDES) permit for the seasonal discharge of treated water to a nearby creek. Compliance to the permit and strict California Title 22 regulations for wastewater reuse required the BVWD to construct tertiary treatment facilities, which included a prefilter to UF. The prefilter had to be simple, low-cost and tolerate difficult water conditions, including summer algae blooms. The BVWD considered Dissolved Air Flotation (DAF) as the prefilter, but it was complicated, requiring substantial investments in capital and energy, which they would need to recover via a 75% rate increase to the community. Seeking a costeffective alternative, the BVWD turned its attention to the Tequatic™ Plus fine particle filter. TUrbIDITY rEDUCTION The BVWD wanted to reduce turbidity from a feed source of >15 NTU to a UF feed quality of <5 NTU. CFT worked closely with the BVWD to not only pilot the filter, but to also test a scaled-down version of the proposed treatment process (see Figure 1). This would enable the BVWD to validate the system, properly size the equipment and see how the filter could tolerate elevated and highly variable total suspended solids (TSS), including algae blooms. Within two months, CFT installed a customized, self-contained mobile pilot unit (see Figure 1) which ran 8–10 hours per day, five days a week over eight months to test seasonal performance. The Tequatic Plus filter was a 2-in unit with a 20-μm TEQUATICTM PLUS Fine Particle Filter Reuse Water Sprayed on Fields Fig 1: Pilot system, Bear Valley Water District filter, designed to produce up to 50 gpm (3.15 L/s) of filtrate. Other operational parameters included feed pressure of 20 psi (1.38 bar) and a pressure drop across the filter of 0.5–2 psi (0.03-0.13 bar). According to the BVWD, the cost of the proposed system using the Tequatic Plus filter was half the cost of the DAF system. The filter was fully automated, unlike other equipment in the system, and consistently and reliably reduced feed source turbidity from 7.0 NTU to 4.1 NTU on average, with no fouling, no backwash cycles, no cartridge filters, and no change or variation in filtrate flow. In addition, delta pressure across the filter usually ran at <1 psi (0.07 bar). This was achieved despite elevated turbidity during the October and November algae blooms (see Figure 2). During this period, the filter reduced turbidity from a high of 14 NTU to 3.9 NTU. The performance of the filter exceeded BWVD expectations while reducing stress on downstream equipment, Raw Water Filtrate - TEQUATIC PLUS Filter Turbidity (NTU) ON 3 APRIL 2013 , Dow Water & Process Solutions announced the opening of a commercial-scale manufacturing facility for the Tequatic™ Plus fine particle filter in Menlo Park, California, which is designed to meet growing demand for its line of F-50, F-75 and F-150 models. Clean Filtration Technologies LLC (CFT), a wholly owned subsidiary of Dow, operates the new Menlo Park facility. Cedella Beazley, CFT general manager, said that "orders are already being filled in a variety of applications where the Tequatic Plus filter is used as a primary filter, a prefilter and pretreatment for applications such as reverse osmosis (RO) and ultrafiltration (UF), or even as a postfilter in applications such as moving bed bioreactor (MBBR) systems." The Tequatic Plus filter (formerly known as the Turboclone™), is a patented technology that combines the power of continuous cleaning, cross-flow filtration with centrifugal separation and solids collection into one device. It is designed to handle a wide range of difficult-to-treat feedwaters having very high and highly variable total suspended solids (up to 10,000 mg/L) much more cost-effectively and consistently than traditional technologies. According to John Patrin, CFT strategic marketing manager, "the Tequatic Plus filter is also proving its value in other markets, such as oilfield water. In addition to low maintenance and high uptime, these customers are attracted to a high water recovery that is typically greater than 99%, low consumables and disposal costs, and low environmental impact." "The Tequatic Plus filter is being used in applications with space and weight constraints, such as prefiltration for drinking water on oil platforms," Patrin said. Aeration Pond Filtrate - Ultrafiltration Filter Year 2008 Fig 2: Turbidity measured for raw water and after Tequatic and UF filtration. May-June 2013 | Desalination & Water Reuse | 35 |

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