For decades, El Paso Water has been using Granular Activated Carbon (GAC) to remove substances that generate color and smell in untreated river water.
But how do you measure which GAC products on the market do the best job? After all, smell and sight are subjective.
Researchers Francisco Solis, Jr. and Juan Canales are working under the direction of UTEP Professor Dr. Anthony J. Tarquin to answer that question in a measurable way, helping EPWater maximize its river water treatment processes.
“We discovered through trial and error that you need 20 parts per million of geosmin, the algae that causes odor, to be noticeable by the human nose,” Solis said. “We started with that ratio, then heated the water because heated water intensifies the smell.”
Solis and Canales ran the algae water through various GAC products that vary by supplier processes, source material and/or granular size; the results showed some were better at removing the odor than others.
To test for removal of the organics that cause color, Solis and Canales used blue, red and yellow food coloring. After running the water through the various GAC products, the samples were put through a spectrophotometer.
The instrument measures the light that is absorbed by the color of the sample and translates it into a number.
The lower the number, the less color is in the water.
Using input from the plant operators, the two researchers are now testing the durability of various GAC products.
Currently, EPWater changes its GAC every three to five years.
But many of the plant operators were convinced that some of the better GAC products could perform well beyond that timeframe.
“They felt that some of the better-quality GAC products could be extremely effective up to 10 years,” Canales said. “So far, the data is proving this theory to be true. We still have several months of tests to conduct, but keeping the GAC in service longer could potentially save the utility and ratepayers millions of dollars.”