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New, simple filtration method could be the answer to zinc

  • Published
  • By John Stuart
  • Staff Writer
Tinker Public Affairs --  Rain clouds unleash their tempest as civil engineering workers crouch near the concrete channel filled with rushing water. They've come to the 1,700-foot drainage ditch near Bldg. 3001 for what's not seen -- the particles of zinc dissolved throughout the water. 
    
It may seem like an undesirable post, but the 72nd Air Base Wing Civil Engineer Directorate environmental technicians are out there every time it rains, retrieving water quality samples. One thing the technicians are testing for is metals.
    
With thousands of square feet of galvanized metal surfaces in the area, storm water runoff containing elevated zinc levels is directed into the lengthy concrete channel and, eventually, into Soldier Creek. But 72nd ABW/CE workers think they might have found a low-tech solution to their problems: dirt and grass. 
    
For the past two years, zinc levels in the runoff water near Bldg. 3001 have consistently exceeded the limits set in Tinker's water quality permit, as governed by the Oklahoma Department of Environmental Quality. This has left 72nd ABW/CE employees searching for technologies to reduce zinc levels within permit limits -- that is, at or below 120 parts per billion. Reducing zinc levels has been a critical concern. 
    
But last week, the 72nd ABW/CE rolled out a new process that should curb zinc levels by as much as 80 percent.
    
"We did some research and found that we might be able to use just soil and grass because soil absorbs zinc, and grass uses zinc as a nutrient," said waste water manager Brandt Fleharty, with the 72nd ABW/CE. 
    
Mr. Fleharty found the idea paging through several industry journals and said the bio-filter technology has shown dramatic results at facilities with similar zinc issues. 
    
"Zinc is a nutrient for all plants, grasses and trees," Mr. Fleharty explained. As such, their solution is to "green" a section of the 1,700-foot drainage ditch by installing a 200-foot section of dirt and grass in the concrete channel. As the runoff pours through the channel, the soil and grass absorbs the zinc out of the water. Zinc is then stored in the blades of grass and crews will merely have to bag the grass clippings to dispose of the zinc. Although completed last week, Mr. Fleharty said they'll have to wait until a rainstorm to test the filter. 
    
The 1,300 square feet of dirt and grass only cost $4,500 to install, a fraction of what other synthetic alternatives cost, which require unattractive chemical processes, Mr. Fleharty said. Additionally, the zinc reducing solution had to be one that didn't attract birds, as the concrete channel runs parallel to the nearby runway. 
    
Drought-resistant Bermuda grass used in the bio-filter is kept alive by the water drainage produced by air conditioner condensation from Bldg. 3001.
    
"We designed the system so the storm water permeates through the soil and through a drain in the bottom," Mr. Fleharty said. "The bottom drain also works to keep the channel dry so we don't attract birds around the aircraft."
    
The all-natural bio-filter is a sustainable practice, and one that exemplifies Tinker's commitment to environmental best practices.