Olsson Associates

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Resolving water quality violations simply

Thursday, June 13, 2013

Sarah Ferdico, Communications

Sometimes, it’s good for engineers to be reminded that the simplest solution can also be the best solution.

“Even though engineers are trained to look at construction and infrastructure solutions to problems, it is our job to consider less-intensive, non-engineering solutions as well,” said Mary Stahl, PE, and senior engineer at Olsson Associates. At the June 2013 American Water Works Association (AWWA) Annual Conference and Exposition held in Denver, Mary presented her solutions for one community’s water quality violation.

A small town on the outskirts of Denver was issued an Enforcement Order by the Colorado Department of Public Health and Environment (CDPHE) because its Total Trihalomethanes (TTHM) concentrations exceeded primary drinking water standards. This small community had extremely limited resources and a restricted amount of physical space for addressing the problem.

Stahl and other Olsson staff members looked at a variety of issues and noticed a few things. First, the water tank was holding over 375,000 gallons of water at a time, when, in fact, 190,000 to 200,000 gallons was sufficient. Although chlorine serves a vital function in water treatment, TTHM problems can arise if water is exposed to too much chlorine or for too long. Olsson recommended decreasing the level of water held in the tank to lower water detention time. Lowering the water age decreased the TTHM’s running annual average by 26 percent.

In conjunction with reducing water age, tighter control on chlorine residual concentrations was needed. Because of the system’s small size, the operators were on site typically once per week. After eight months at the lower storage levels, it became clear that a chlorine monitor with a feedback loop for control was needed to provide the tighter control on chlorine residual. A chlorine analyzer, at modest cost, was added to the system. The first sample result taken recently indicates a significant decrease in TTHM concentrations and is well within drinking water standards.

As Mary stated at the AWWA conference, water engineers are trained to resolve issues through engineering and additional infrastructure. Often, a water treatment facility needs additional tanks, pumps, or treatment processes to better function. However, this example of the small community with the TTHM problem is a reminder to all engineers that, sometimes, simple, non-engineering solutions are just as effective and can be a better solution for the utility.

Olsson has 57 years of experience working with small communities to find cost-effective solutions to public infrastructure problems. Feel free to contact Amber Kauffman at 970.461.7733 or at akauffman@olssonassociates.com if you have any questions.

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