Water. Desalination + reuse
Issue link: https://fhpublishing.uberflip.com/i/107143
REGIONS The five partner agencies in the Bay Area Regional Desalination Project Predicted future water-supply shortages in the BARDP agencies advanced treated recycled water for indirect potable reuse, such as groundwater recharge l SFPUC – Encouraging private developers to integrate cuttingedge water-reuse in new large-scale construction through a streamlined permitting process and grant funding l Zone 7 - Evaluating the expansion of recycled water to maximize its use for irrigation l CCWD - Evaluating new opportunities for recycled water development. The partner agencies estimate shortages during the period 203040 ranging from 39,000 acre-feet (AF)/year (48 million m3/y) to 217,000 AF/y (268 million m3/y). In a multi-year drought, EBMUD could be short of 100,000-120,000 AF/y (123-148 million m3/y). It is in response to these long-term scenarios that the agencies are committing to additional conservation as well evaluating other reliable water supplies such as desalination. With the long lead time water supply projects require to plan and implement, the time is now to consider all alternatives. capacity. This storage could provide flexibility to optimize and increase the BARDP yield. The intake of the desalination plant would rely on a combination of new or modified water rights (ie, water rights from CCWD and/ or other nearby municipalities), based on availability. One of the options for disposal of the desalination plant brine is blending with discharges from wastewater treatment plants located in the vicinity of the desalination plant, including the Central Contra Costa Sanitary District and the Delta Diablo Sanitation District. Power to the desalination plant could be provided by Pacific Gas & Electric, the current power supplier at Mallard Slough Pump Station, or nearby power plants and/or sources of renewable energy. The partners are committed to reducing the carbon footprint of the BARDP. One of the key tasks of the ongoing SSA is therefore a greenhouse gas analysis. This is the project's preliminary estimate of attributable energy use. PROjEct uNdER Study The site under consideration would divert water from the Sacramento-San Joaquin Delta at the Mallard Slough Pump Station, located in eastern Contra Costa County, to produce 20 MGD (75,000 m3/d) of desalinated water for delivery to the partners. Water produced by the BARDP could be blended with supplies from CCWD, EBMUD (via the Mokelumne Aqueducts), or both. Zone 7 and SFPUC would receive water passed through EBMUD through interties (one future and one existing, respectively), and SCVWD could receive water either as a Delta transfer/exchange with CCWD or passed through SFPUC and delivered through an intertie at Milpitas. The water from the BARDP could be treated by one-pass or two-pass reverse osmosis (RO) and may require further treatment (stabilization, pH adjustment) depending on the delivery point into either the CCWD or EBMUD system. Other individual/satellite type of systems were considered but rejected. A single location at Mallard Slough is the most efficient in terms of environmental footprint, lower energy use, costs and other benefits. This location takes advantage of existing facilities and does not need new facilities built, which itself has benefits. The proposed BARDP would operate continuously irrespective of climate conditions, with the possibility of storing water (including by exchange or transfer) in CCWD's Los Vaqueros Reservoir when demand from the partners was less than plant Mallard Slough desalination Energy Estimate Intake Annual average typical year kWh/acre-foot* 275 1,250 Wet season (May: 1,000 mg/L of total dissolved solids (TDS) salinity: 900 Dry Season (December: 4,800 mg/L of TDS salinity): 1,500 Very Dry Period (Summer: 11,600 mg/L of TDS salinity): 2,700 Energy to Pump to CCWD's Customers (MPP Line) Total Energy Needed (per acre-foot of water) Energy Needed Per Household Per Year (if supplied SOLELY by brackish-water desalination) 600 2,125 1,060 *1 acre-foot = 1233.6 m3 Around 95% of the work in the SSA, which was agreed in October 2011, will be completed in-house by the partner agencies. As well as technical analysis, the project will be refining cost estimates and taking part in public outreach exercises like those held in March (organized by the Sierra Club Bay chapter) and in Redwood City in May. The US$ 1 million SSA budget will be shared equally by the partners, who each have their share of work to complete. Preliminary results are expected to be available in early 2013 with recommendations being made to the partner agencies in mid 2013. D&WR wishes to thank Hasan Abdullah of EBMUD for his help in the compilation of this feature. Further info is available on the project website, www.regionaldesal.com l August-September 2012 | Desalination & Water Reuse | 31 |