Granite Shoals Utilities Superintendent Josh Hisey observes the clarification tank at the city’s water treatment plant. Hisey is standing on a new safety catwalk that was installed using a $300,000 Community Development Block Grant. The federal money went toward upgrading equipment used in the city’s water disinfection process. Staff photo by Dakota Morrissiey
Upgrades to Granite Shoals’ water treatment process are in place and awaiting final approval from the Texas Commission on Environmental Quality.
Chlorine dioxide-generation equipment and a safety catwalk at the city’s water clarifier were installed using a $300,000 federal Community Development Block Grant awarded in 2019. The city matched the grant with $60,000 of its own money.
Granite Shoals is switching from a “free chlorine” disinfectant to a “chlorine dioxide” disinfectant. Chlorine dioxide is more effective and efficient, which will help the city meet and surpass TCEQ water quality standards, said Interim City Manager Peggy Smith.
“It’s a long-term solution,” she said. “We are controlling disinfectant byproducts with free chlorine treatment at this point. But as the lake continues to change, switching to the chlorine dioxide treatment is a better solution for us to stay within regulatory limits for our community.”
Lake changes to which Smith referred are the levels of organic material in Lake LBJ, the source of the city’s drinking water. Drought conditions, lake levels, floods, and heavy rain all contribute to the amount of organic material in the lake. The larger the amount the more difficult it is to properly disinfect and filter the city’s drinking water.
Currently, Granite Shoals uses free chlorine, an effective and widely used disinfectant, but one that allows a certain amount of organic material to pass through the water treatment process. The free chlorine-disinfection process creates molecules called trihalomethanes, unstable chlorinated organic compounds that can be harmful to humans in large quantities. While Granite Shoals has been within TCEQ water-quality standards of 0.080 milligrams per liter of trihalomethanes, the new chlorine dioxide disinfectant will be even more effective.
Chlorine dioxide actually breaks down the cells of organic material through oxidization. By the time water reaches clarification and filtration, more harmful organic material is eliminated and far fewer trihalomethanes are created.
Chlorine has been used to disinfect water since 1908, according to the Centers for Disease Control and Prevention. It is present in most drinking water treatment systems in the country and kills harmful disease-causing viruses, bacteria, and microorganisms that otherwise would contaminate drinking water pulled from lakes and reservoirs.
“Chlorine is one of the greatest things to happen to public health,” Smith said. “Without chlorine in the water, anything and everything in our lake would pass on and affect public health.”
The chlorine dioxide-disinfection process will not affect the water’s taste, according to Granite Shoals Utilities Superintendent Josh Hisey. The raw water that comes out of Lake LBJ could be measured at a 10 in turbidity, while the water that ends up flowing from your faucet could be measured at a 0.01. Turbidity is used to measure the clarity of a liquid.
Use of the chlorine dioxide-generation equipment is on hold until TCEQ gives final approval on the city’s plans and adjusts the city’s permitted disinfection process from “free chlorine” to “chlorine dioxide.” Smith cited staffing issues and backed-up permitting applications at TCEQ as causes for delayed permit adjustment, but she is confident that approval will be given.
For more information regarding water quality standards, visit TCEQ’s website.