World’s largest advanced wastewater purification system prepared for indirect potable reuse
McCarthy Building Cos. Inc. recently began construction of the initial expansion of the groundwater replenishment system for the Orange County Water District (OCWD) in California. Located at the OCWD Advanced Water Purification Facility (AWPF) in Fountain Valley, the $142.7 million project will create an additional 31,000 acre-ft per year of new water supplies to serve north and central Orange County. Once completed, the AWFP’s total production will reach 103,000 acre-ft per year, enough water for 850,000 people.
A joint project of OCWD and Orange County Sanitation District (OCSD), the groundwater replenishment system takes highly treated wastewater that would have normally been discharged into the Pacific Ocean and purifies it through a three-step process that includes microfiltration, reverse osmosis (RO) and ultraviolet (UV) light with hydrogen peroxide. About 35 million gal of near-distilled quality water per day is pumped into injection wells where it serves as a seawater intrusion barrier. Another 35 million gal per day is pumped in a 13-mile-long pipe to OCWD recharge basins in Anaheim, Calif. The water then filters through sand and gravel to replenish the deep aquifers of Orange County’s groundwater basin and ultimately becomes part of the drinking water supply.
The project entails expansion of the existing microfiltration facility by constructing eight new below-grade treatment basins and enlarging the existing basement facility. Other work includes construction of a new 32,000-sq-ft RO building, the installation of five new UV treatment trains to match the existing systems, as well as retrofitting the existing post treatment systems to employ a new lime feed system. McCarthy will also construct two above ground steel tanks, each is 215 ft in diameter with a height of 35 ft and a capacity to hold 7.5 million gal of water.
The system is the largest advanced water treatment facility of its kind in the world and has garnered more than 35 regional, state and international awards, including the American Society of Civil Engineers (ASCE) 2009 Outstanding Civil Engineering Achievement Award for the year’s most outstanding national engineering project, and the Stockholm 2008 Industry Award for the year’s most outstanding international water project. Construction work is scheduled to complete in September 2014.