From rubberized asphalt to civil engineering projects to fine-mesh rubber powders, rubber industry experts have found myriad uses for scrap tires in which the tire rubber improves the quality of the goods or services involved.
An engineering professor, however, has come up with another promising use for crumb rubber from scrap tires:waste water filtration.
Yuefeng Xie, associate professor of environmental engineering at Penn State University-Harrisburg, has performed several studies demonstrating that scrap tire crumb rubber can filter 20 to 30 gallons of waste water per minute per square foot of filter, compared with the five gallons per minute achieved by a typical sand/anthracite filter. Such increased volume, he claims, could save municipalities and waste water treatment plants a considerable amount of money annually.
Xie, a specialist in waste water treatment with more than 20 years of professional research experience, said he first thought of using crumb rubber for waste water filtration about eight years ago, while discussing the scrap tire abatement problem with a friend.
"At that time, we were just trying to find an alternative way to get rid of scrap tires," he said. "We weren't thinking of it as a way to improve waste water filtration. But when we tested it, we were amazed."
The key to crumb rubber in waste water filtration is that it is flexible and easily compressible, according to Xie. It has a bigger pore size than sand or anthracite, meaning that it allows much more water through initially than a sand/anthracite filter and becomes more compressed toward the bottom, straining the water much more rigorously. These qualities make it ideal for waste water filtration, he said.
To date Xie has installed a temporary waste water filtration system in the town of Palmyra, Pa., and has had several ongoing filtration projects on his campus. He has presented the results of his research in several professional forums, including the Fall 2001 ACS Rubber Division meeting in Cleveland.
Xie has not experimented with crumb rubber filters for water intended for drinking, and does not intend to, he said. But he believes the process shows great promise for recovering waste water for irrigation, landscaping and similar purposes.
No one is using crumb rubber filtration commercially or on a large-project basis at this point, according to Xie. But a couple of storm water treatment companies have called him expressing interest in the process, he said.