Water. desalination + reuse

PROJECTS | 26 | Desalination & Water Reuse | February-March 2014 PROJECTPROGRESS CaRlSbad SWRO fiRST yEaR milESTOnES REvEalEd Following the early January celebration of the first year of construction of the Carlsbad seawater reverse osmosis desalination plant in California, developer Poseidon Resources provided D&WR with a breakdown of the work so far. The 50 MGD (189,000 m ³ /d) plant, which is on schedule and on budget, is due to start producing water in 2016 and will be the largest desalination plant in the Western Hemisphere. The following is the construction progress: • Intake (~10% total) • Pretreatment (~40% total) • RO (~10% total) • Product water tank (~20% total). In addition, some of the process equipment is beginning to show on site. The plant is being constructed by Kiewit Shea Desalination Contractors with IDE Technologies providing the desalination expertise. biWaTER gETS baRClayS baCking fOR CaRibbEan SWRO PlanT A Caribbean water and wastewater project, including a 10,400 m 3 /d seawater desalination plant, has received financial backing worth US$ 43 million from Barclays, backed by a UK Export Finance Guarantee (UKEF). UK contractor Biwater has informed D&WR that its contract for supply of a desalination plant for the island of Tortola in the British Virgin Islands will be on a build–own- operate-transfer (BOOT) basis. The seawater reverse osmosis (SWRO) system will be a two-pass system running at 45% recovery. It incorporates four first-pass trains and two second-pass trains and is designed to run at 100% capacity with one train from each pass down for maintenance. However, normal operation will be to run at 100% capacity using all trains, which is the optimal and most efficient mode. The BOOT contract for the plant has a 16-year water purchase agreement, which will come into effect when the plant first produces 2.3 MIGD (10,400 m 3 /d). Biwater is utilising energy recovery, including pressure exchangers, high-pressure pumps and booster pumps for the SWRO trains. Pretreatment consists of a two-stage media filtration followed by 5 μm cartridge filtration to protect the system from foulants. Biwater AEWT is the RO plant supplier; equipment is being supplied from California, USA. Barclays acted as the sole advisor, arranger, lender and facility agent. In addition, the project was fully supported by the UK government export credit agency UKEF and required close collaboration between both UKEF and the British Virgin Islands' Government. mOnTEREy bOREhOlES REvEal gOOd SlanT-WEll COndiTiOnS California American Water (Cal Am) reported on 20 December 2013 that data from its ongoing investigation into subsurface slant well intakes for its proposed Monterey desalination plant was showing promising results. Over the last four months, Cal Am has drilled eight geotechnical boreholes in three areas along the Monterey coast in its study of preferred sites for a subsurface intake for its Monterey Peninsula Water Supply Project. This will be based on a seawater desalination plant of 6.4-9.6 MGD (24,000-36,000 m³/d) capacity. Two of the three drilling sites – Potrero Road and further down the coast on property owned by Cemex Ltd – show highly favorable conditions for locating the subsurface slant wells. The Cemex boreholes indicated an almost continuous layer of sands and gravels to a depth of 240 ft (73 m). The Potrero Road boreholes revealed a thick layer of clay at a depth of approximately 140 ft (43 m), indicating a separation, also known as an aquitard, between the proposed ocean intake zone above and the lower aquifers. "The results thus far are very promising," said CalAm director of engineering Rich Svindland. "At the northern site near Potrero Road, we have a nice, deep layer of sand filled with salt water with a well-formed aquitard below, which, if drawn from, would likely avoid impacts to the Salinas Basin. At the Cemex site we have a very thick sand layer below the ocean floor, which will work nicely for the subsurface slant-well seawater supply. The third site, at Moss Landing, was not as promising. There, intermittent clay layers mixed with silt and fine sand, without enough continuous sand layers to use any type of subsurface intake system efficiently. Although Moss Landing was not one of Cal Am's preferred intake locations, the company agreed to drill boreholes there as part of a settlement agreement to study alternative sites proposed by private developers. "Now that we have affirmed sufficient geological conditions, we will install a test slant well under the ocean floor to assure we have suitable water flow and quality for a fully operational desalination plant," Svindland added. Additional onshore monitoring wells will be drilled in and around the test slant well site to monitor the well's effects on surrounding groundwater aquifers. California American Water has proposed the variable-sized desalination facility as part of its three-pronged project to address the Monterey Peninsula's impending water supply shortage. The proposal also includes aquifer storage recovery and recycled water projects, which are presently advancing in planning and development. CDM to build US$ 87 million Monterey plant – see page 8. SEvEn SEaS filES EiS fOR ChilE SWRO … An environmental impact study (EIS) has been filed by Seven Seas Water Chile SpA for the Bahía Caldera Desalination Plant in Chile's Region III. The project involves construction of a reverse-osmosis (RO) plant that will have a desalinated water production of approximately 2.1 MGD (7,949 m 3 /d) in its first phase. The plant

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