City considers solutions for wastewater treatment plant odor


By Rachel Madison

Ongoing complaints of odors coming from the Liberty Hill wastewater treatment plant have prompted city officials to investigate potential solutions for mitigating those odors.

The treatment plant has been open since 2006. An expansion project on the plant began approximately four years ago and is set to be finished in July. Backing up directly to the wastewater treatment is the Grayson subdivision, which first started building homes in 2017. Residents in that neighborhood have been complaining about the odors emitting from the plant since at least 2019.

City Administrator Lacie Hale gave an update and timeline from public works on potential solutions for the odors at the most recent city council meeting on June 9. Council member Angela Jones had asked for this item to be placed on the agenda so that community members—particularly those who live in Grayson—could be updated on what the City is doing to try to resolve the issue.

“We believe the odors are coming from the headworks box and the [sequencing batch reactor], which is the oldest infrastructure we have out there,” Hale said. “The headworks box is where the effluent comes into the plant to be treated. If the wind is right or the sun is out, there is an odor.”

The sequencing batch reactor is set to go offline in approximately two weeks when the expansion project at the plant is complete and the new equipment goes online.

“The odor coming from that should go away because it won’t be a treatment facility anymore,” Hale said.

In order to mitigate odors coming from the headworks box, the City has installed metal sheets, odor misters and a plastic curtain around the headworks box. In addition, an air scrubber has been installed to essentially filter the air surrounding the headworks box, Hale said.

“We’ve done quite a bit,” she added. “These are the things we’ve done to mitigate the odors.”

The latest installation of the plastic curtain around the headworks box has made a difference in the odor levels, Hale said, but she has also recently heard from a few Grayson residents in the last couple of weeks that there is still an odor.

“We are doing everything we can,” Hale said.

Jones added that the smells coming from the plant are consistent—not just during hot days or when the wind is blowing the right direction, but she is hopeful that when the old infrastructure goes offline, it will help to reduce the odor.

“Do we have any idea how much that’s going to help?” she asked. “Will it take the odor away completely?”

City officials did not have an immediate answer, instead citing a desire to conduct a study to find out exactly where the source of the odor is coming from and if there’s another way to mitigate it. City Engineer Curtis Steger said it’s possible that other locations within the plant could be generating odor, but he believes most are coming from the headworks box.

Hale added that a study, which she estimates would cost about $5,000, would allow the City to measure the odor constituents and strength and develop a comprehensive plan to address the problem areas.

“When you’re out there, it doesn’t have an offensive odor,” Steger said. “It’s kind of a musky smell, but when wastewater comes in through the headworks and there’s a lot of turbulence and the releasing of hydrogen sulfide, it smells. Hydrogen sulfide is something the human nose picks up very easily.”

Council member Kathy Canady said she’s not discounting the need for the City to do what it can to lessen the odors, but because the plant was there before the subdivision was built, she believes there will always be some odor in the air.

“We are doing the best we can, but unfortunately, plants just smell,” she said.

Council member Crystal Mancilla suggested the City wait on beginning a study until the sequencing batch reactor goes offline in a couple of weeks to see if there is a noticeable difference in the amount of odor coming from the plant.

Council member Chris Pezold suggested looking into the costs of landscaping to put in a berm and trees along the side of the plant that backs up to Grayson.

“When the wind blows, if you can get it higher than the houses, it’ll push it up and dissipate,” he said.

The Council decided to table the agenda item until the sequencing batch reactor goes offline. From there, they will decide if a study is needed and will also explore landscaping options. Jones also asked city staff to provide an update to Grayson residents about what the city has done and plans to do in the future to mitigate the odors. A letter as well as a text through Liberty Hill’s utility services will be sent to every Grayson resident.