A monolithic layered nonwoven–woven geotextile for use with drainage geocomposites in coal combustion residual projects

A layered monolithic filter consisting of a nonwoven needlepunched and a woven monofilament geotextile is presented in this paper. The two geotextiles are mechanically bonded in a needlepunching process to produce a hybrid geotextile on a commercial scale. The fuzzy woven side of the geotextile, resulting from the needlepunching process, is ideally suited for lamination to a geonet, although a standalone filter application is also possible. Filter press tests on the geotextile against a fly ash slurry of 500% yielded a retention efficiency of 99.6%. Gradient ratio values of 1.0–1.5 and hydraulic conductivity ratio values of 0.5–1.0 were obtained against fly ash and FGD gypsum from four power plants. Four field basin tests were performed under the CCRs wherein effluent parameters of total suspended solids, total dissolved solids, turbidity, conductivity and pH were monitored with time. The field tests showed that the fly ash and FGD gypsum contained in the test basins were not migrating with time.