The Bexar Metropolitan (BexarMet) Water District in Bexar County, Texas, expanded the capacity of its ultrafiltration plant in July. The expansion boosted the production of the plant by 4.5 million gallons per day, helping to meet the water needs for the county's growing population.

The BexarMet Ultrafiltration Water Treatment Facility opened in December 1999 to treat surface water from the Medina River. Previously, BexarMet's 250,000 customers relied on groundwater from the Edwards Aquifer, but, as development and ongoing droughts taxed the aquifer, the water district sought alternative water sources. “There was some need for regulation of the Edwards Aquifer because of the growth and the demands that were being placed on it,” says Chuck Ahrens, deputy general manager for BexarMet. “A state agency was created to issue permits to all the water users to limit how much water we can withdraw from the aquifer. That presented a challenge to us to have to go out and develop other sources of water to accommodate not only for growth but also this reduction in our use.”

BexarMet created a non-profit corporation to contract with Harrington Park, N.J.-based United Water to design, build and operate the ultrafiltration plant. The $30 million plant, which was completed in 16 months, draws water from the Medina River and removes solids, organics and pathogens by forcing the water through a series of thin membranes. The ultrafiltration process requires fewer chemicals and occupies approximately one-quarter less space than traditional water treatment plants.

When the plant went online, it produced approximately 10 million gallons per day for 33,000 homes and businesses in south San Antonio and south Bexar County. “That displaced some of our Edwards Aquifer demand and provided for some growth, but we have to continue,” Ahrens says. “Our work is never done in this quest to acquire additional water rights and additional means to provide water to the customers.”

To expand the plant's capacity, the water district acquired rights to pull 19,000 acre feet of water per year from Medina Lake, which flows into the Medina River. It also installed larger pumps at the treatment plant, and the filters were re-rated by the state to accommodate increased flow. The expansion took 12 months to complete and cost approximately $650,000. As a result, the plant can produce 14.5 million gallons of water per day, which is sufficient for the current population and enough to accommodate growth in the area. “We want to make sure for those businesses and for those families that reside or work in the BexarMet-served areas that we approach it with a belt and suspenders,” Ahrens says. “If we get into a drought and one source is regulated, then we have backup.”

Unlike the Edwards Aquifer, Medina Lake and the Medina River are not subject to the same water use restrictions during droughts, so residents and businesses in south Bexar County enjoy a steady water supply from the ultrafiltration plant. “We think that's really important as it relates to economic development for this area, because San Antonio is experiencing a lot of growth, and we expect that trend to continue,” Ahrens says.

With the expansion, the ultrafiltration plant is operating at capacity. The water district is considering alternatives for expanding water production in the area, including constructing an additional water treatment building on the same site as the ultrafiltration plant or closer to Medina Lake. The county's population is projected to reach 1,458,000 by next year and grow to 1,674,000 by 2015. “We were very excited when we opened this facility, and we were once again pleased that we were able to increase its production and continue our expansion of our water inventory,” Ahrens says. “[We] are hopeful that we are able to continue doing additional upgrades to address not only the reduction in our Edwards Aquifer use, but also accommodate for the growth in this area.”