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Carollo and Zone 7 Water Agency collaboration designs innovative demineralization plant
The Zone 7 Water Agency of Livermore, Calif. recently received the “2012 Membrane Plant of the Year” Award from the Southwest Membrane Operator Association (SWMOA) for their Mocho Groundwater Demineralization Plant. The award honors public or private facilities providing water, wastewater or reclaimed water that show exemplary safety records and clean premises, possess minimal permit violations, utilize their plant to educate the public and have at least 1 million gal per day (mgd) of membrane-based treatment processes.
Carollo Engineers Inc., the largest water-related engineering firm in the United States, worked alongside the Zone 7 Water Agency to construct the Mocho Groundwater Demineralization Plant in response to the salt and mineral accumulation in the Livermore-Amador Valley’s main groundwater basin. The San Francisco Bay Regional Water Quality Control Board approved this plan in 2004, and the facility began operating in August 2009. The plant was designed to utilize reverse osmosis in order to reduce salt and mineral buildup in the Livermore-Amador Valley Main Groundwater Basin.
“SWMOA is a Membrane Plant Operators Association, so the award is really about the terrific job that the plant staff does,” says Tom Seacord, associate vice president, Carollo Engineers Inc. “It was a great pleasure working with the Zone 7 staff during the design and construction of this facility. For a design to be successful, you need the input of the owner and operations staff. This allows the design to be the most responsive to their needs. Zone 7’s staff gave our design team this integral support.”
As part of the project, Carollo also designed a 28-in. diameter high-density polyethylene pipeline, which was constructed to convey water from four separate wells into the Mocho Groundwater Demineralization Plant. During the treatment process, the agency employs reverse osmosis, a method used to remove dissolved salts from water. After, the treatment process produces a very soft permeate water which is further treated by a decarbonation process before being disinfected and chemically treated to prevent corrosion. The process also produces a rejected brine stream (containing the removed salts), which is collected for disposal. Currently, the Mocho plant operates at 80% efficiency, turning 6.1 of the 7.7 mgd raw water pumped through its system into softened permeate. Eventually, the facility will be able to increase its efficiency to 85%. This unique process was a vital piece to the agency’s award submission.