Texas water treatment plant implements progressive plan for dwindling water supplies
From the outside, the building looks like it is straight out of the 1920s, with retro architecture, curved arches and exposed red brick. But go inside, and it is evident that the Bachman Water Treatment Plant in Dallas is anything but outdated.
With an abundance of upgrades—including a $400-million systemwide pipe replacement—Bachman is well equipped for modern times, thanks to a massive project that began in 2003, according to Senior Program Manager Ken DelRegno.
Keeping Up With The Times
Bachman is an advanced softening plant that opened in 1929 to treat water from Lake Dallas after White Rock Lake, the source for the city’s first treatment plant, ran dry 85 years sooner than anticipated.
Originally, Bachman’s capacity was about 30 million gal per day (mgd), but it has been upgraded several times since. When it converted to ozone disinfection technology in 2003, the plant expanded to its current capacity of 150 mgd.
“It’s our smallest plant, but it’s probably the most strategically situated. It’s right in the heart of Dallas,” DelRegno said. “It puts the supplier in a very critical area, because our other plants are a long way from town.”
In the past decade, Bachman has added a new SCADA system, ozone treatment, a high-lift pump station and a new clear well; built a third secondary basin and a new low-lift pump station; completely reconditioned and rebuilt the filters; installed new chemical feeds; and renovated several older buildings, turning an old pump station into a maintenance facility and an old chemical building into a control complex.
The plant also took advantage of an old ski jump lake, diverting the Elm Fork Trinity River through the lake and using it as a pre-sedimentation basin.
DelRegno added that the plant is converting to an enhanced coagulation biological filter due to issues with modification and the distribution system, which he said are Bachman’s biggest challenges.
In 2004, the system started having issues with red water. A water quality study revealed that nitrification was present and it was occurring due to lack of proper chemical feeds control.
“If you overfeed ammonia, then that’s the seed for nitrifying bacteria to convert it; and you wind up with a nitrification loss of chlorine residual and a drop in pH, and ultimately, some red water issues,” DelRegno said.
As a result, part of the equipment changeover included a flow-based chemical feed, according to DelRegno. Chlorine ammonia monitors also were installed throughout the plant to monitor chlorine, monochloramine and free ammonia.
The Bachman plant also uses orthophosphate as a corrosion inhibitor. “That hopefully will stop when we get the biological filters in,” DelRegno said.
An Uncertain Future
“Texas has no natural lakes, so every water supply here has to be a manmade impoundment or groundwater,” DelRegno said. “And Dallas uses no groundwater.”
That means the city must be proactive when planning for future water supplies. “In 2000, we had a peak day of almost 800 million gal in one day, and we decided that we needed to get busy with conservation,” DelRegno said.
The next year, the city started time-of-day watering restrictions. “That made a huge dent. In fact, our highest [use] day since then has been about 660 mgd, and last summer was the second hottest summer we’ve ever had.”
Recently, in an effort to support long-term water conservation, the Dallas City Council passed a permanent twice-weekly watering restriction. DelRegno said that although conservation is necessary, it impacts revenue, and consumers usually are unhappy about it—their water supplies are limited and rates are higher. This makes cost another one of Bachman’s chief concerns.
To prepare for the future, the plant completed a long-range water supply study that looks 50 years into the future. According to DelRegno, the study has helped immensely and has led to plans that will ensure the city’s water supplies stay strong in years to come. “That’s why we still have two lakes sitting in East Texas that we’re not using water from,” he said. The city pays for the upkeep, and the supplies will remain unused until Bachman needs the water.
Despite the best efforts to plan for the future, however, DelRegno said more needs to be done. “Long term, you look 30 years out, and this area’s in big trouble. It’s very dry here, and there are 25 million people in Texas now,” he said. “It’s going to be a difficult thing going forward to come up with enough water to deal with that.”
http://www.wwdmag.com/sites/default/files/imagecache/article_slider_big/Picture%20001.jpgThe original headhouse, constructed in 1929, houses the laboratory and administrative offices.
http://www.wwdmag.com/sites/default/files/imagecache/article_slider_big/Picture%20003.jpgOverview of flocculators and sedimentation basins.
http://www.wwdmag.com/sites/default/files/imagecache/article_slider_big/Picture%20004.jpgThe new operations control center.