The Penn State Research Foundation and Associate Professor of Environmental Engineering Yuefeng Xie were assigned a U.S. patent for a method of using waste tires as a media to filter water. &quotThe crumb rubber could be used for treating wastewater, ship ballast water, and stormwater,&quot Xie said. The technology also reduces the amount of scrap tires and promotes recycling and green engineering.

For traditional wastewater filtration using gravity downflow granular filters with sand or anthracite as a medium, backwashing the filters can cause clogging as larger particles settle toward the bottom of the filter bed and the smallest particles end up on top. Through the crumb rubber method, the larger solids are removed at the top layer of the filter and the smaller solids at a lower level, greatly minimizing the clogging problem, according to Xie. Because the crumb rubber is compressible, the porosity of the particles is decreased. It can then be used at higher filter rates while performing similarly to other media now in use. The crumb rubber media provide better effluent qualities and larger media allow longer filter runs at higher flow rates.

Several studies conducted by Xie reportedly show that the crumb rubber filter is more cost effective than conventional sand or anthracite filters. Because of substantially greater water filtration rates and lighter weight compared with sand or anthracite, crumb rubber filters may also be used in a mobile treatment units for disaster relief operations, he said.