Water system chemical use aim of study

Tulsa hopes UA finds way to cut ammonia in filtering

University of Arkansas researchers are working to refine a commonly used drinking-water filtration process to reduce dependence on powerful chemicals.

Julian Fairey, an assistant professor of civil engineering at the university, is leading the two-year research project, which is funded through a $156,000 grant from the Tulsa Metropolitan Utility Authority. The project kickoff date wasSept. 1.

“Right now, we are madly buying supplies and equipment to set up laboratory-scale studies,” Fairey said. “We’re simulating what’s happening in a water plant.”

Fairey said he is being assisted by Thien Do, a third-year graduate student who is pursuing a doctorate under Fairey. Wen Zang, also an assistant professor of civil engineering at the university, is part of the research team as well.

Roy Foster, the water-quality assurance manager for Tulsa, said the city offered the grant funding to address potential side effects of the city’s system of disinfecting its drinking-water supply.

Tulsa, like most metropolitan areas in the United States, uses chlorine to disinfect the raw water supply, killing bacteria and making it safe for drinking. While the process produces safe drinking water, some dissolved organic matter in the raw water can chemically bind with the chlorine, producing trihalogenated methanes. These methanes are classified as “disinfecting byproducts” by the federal Environmental Protection Agency.

“What we’re trying to do is identify specific natural organic matter that are precursors for these byproducts,” Foster said.

“We chlorinate water to kill bacteria,” Fairey said. “Disinfection is a wonderful thing, and we don’t want to compromise - but like a lot of wonderful processes, there are potentially dangerous side effects.”

In high-enough combinations, these byproducts have been found to be potential carcinogens, and may lead to liver and kidney problems.

Monitoring data from the Oklahoma Department of Environmental Quality show that the amount of total trihalogenated methanes (TTHM) in periodic water samples in the Tulsa area, taken in 2011, range from as little as 13.4 micrograms per liter to as much as 91.5 micrograms per liter. The majority of the samples contained fewer than 40 micrograms per liter of TTHM.

The limit for TTHM set by the EPA is 80 micrograms per liter, said Michele Welsh, public water supply compliance tracking officer for the department.

The EPA’s Region 6 office in Dallas began maintaining data on water sampling data in the Tulsa area in 2012, but that data are currently unavailable because of the federal government shutdown.

The initial phase of Fairey’s research will focus on trying to identify as much of the dissolved organic matter in Tulsa’s raw water as possible. Once Fairey feels the inventory is adequately representative of the water system’s organic contents, the researchers will begin designing a granular activated carbon filter engineered to capture and remove the organic matter specific to Tulsa’s water system.

“We’ll purchase activated carbon filter material that’s available commercially, then modify them in my lab,” Fairey said. “We’ll be heating them and exposing them to aggressive chemicals to modify their pore structure and surface chemistry.”

Foster said Tulsa currently combats levels of TTHM in its water by adding ammonia to the drinking water, which binds with the chlorine, forming monochlorine, which in turn curbs the formation of TTHM. Foster said his hope is that Fairey’s team will produce a technological adaptation that makes the addition of the ammonia unnecessary.

“The cost savings would be minimal, but it would improve safety for the workers in the water-treatment plant, because it would be one less chemical they have to deal with,” Foster said.

“Another reason we’re evaluating the treatment process is that the science and technology is advancing at a quicker pace than regulatory environment,” Foster said. “There may be disinfection byproducts we could be producing, but aren’t regulating. We’re trying to optimize the safety of the water.”

According to city website, the two water treatment plants process between 90 million and 190 million gallons of drinking water each day, drawn from the Eucha-Spavinaw and Oolagah lakes. The city supplies drinking water to about 500,000 residents. In 2012, the plants pumped more than 41.1 billion gallons of treated drinking water to area residents, according to the website.

Northwest Arkansas, Pages 9 on 10/09/2013

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