The city of Tomball, Texas, is located in the heart of Houston’s oil country. Quality of life in Tomball depends in no small part on the quality of its water, and on the performance of the city’s two wastewater treatment plants, which serve a growing population of more than 10,000 residents. In late 2013, operators of the 1.5 mgd South Plant found themselves facing increasing maintenance issues with three brush aerators operating in the plant’s two-channel oxidation ditch. The aerator failures were threatening to compromise effluent quality and environmental compliance.
A trying situation
In January 2014, these breakdowns were at a critical point, and the city concluded that the aerators were reaching the end of their useful life. “It was pretty trying,” says Glen Williams, plant supervisor. “We had to rent floating aerators while we were repairing the brush units in order to maintain compliance.”
When the municipality secured funding to replace the aerators, plant management contacted Evoqua. Upon evaluation of the facility, Evoqua determined that existing tank widths were ideal for Envirex Disc Aerators. Envirex Disc Aerators use nodules and dimples molded into disc surfaces to transfer energy and oxygen into wastewater.
Efficient and reliable
More efficient and more reliable than brush aerators, disc aerators are recommended as replacements for brush aerators. The replacement is a simple retrofit for contractors using the existing tanks. The discs allow for improved mixing efficiency, lower energy use, simpler operation and less maintenance. In addition, access platforms to drives and outboard bearings make disc aerators easier to maintain. Since the HIPS plastic discs do not deteriorate or corrode like carbon steel brush aerators, the disc system has a significantly longer operating life.
Tomball had limited experience with disc aerators, and asked Evoqua to provide parallel proposals for brush and disc solutions so they could evaluate them side by side. Evoqua supplies both aerator types as retrofit solutions that require relatively minor engineering.
After investigating the choices and evaluating nearby disc aerator installations, Tomball chose to replace the first of its three aging brush rotors with an Envirex disc unit. Evoqua installed the unit in 2014.
After startup, plant operators noted reduced noise, fewer mixing “dead zones” and fewer odors due to the disc aerator’s superior mixing and oxygenation. Energy consumption was also reduced. And, most important, according to Williams, “We haven’t had any compliance challenges since.”
A clean sweep
After the evaluation, Tomball decided to replace its remaining two brush aerators with Envirex Disc Aerators as well.
“All of our brush units were at end-of-life,” says Williams. “We were satisfied with the performance of the Evoqua disc unit, and decided to move ahead.”
The two additional units were ordered in the fall of 2014 and are now in place. Since the disc aerators have been installed, the focus of the plant’s maintenance staff has shifted from emergency maintenance of the old system to preventive maintenance of the new system — a much less stressful, less costly way to operate.
For more on the Envirex Disc Aerators, click here.