Hydraulic compatibility of geotextile-compost systems in landfill covers

Abstract

Landfill covers are required by federal regulations to cap municipal solid waste and prevent leachate formation. The use of compost as part of a vegetative layer in landfill final covers is one way to improve the sustainability of landfills. In order to successfully use compost in landfill cover applications, hydraulic compatibility of the compost and underlying geotextile filters must be adequate. The hydraulic compatibility of various composts and geotextiles have been explored through laboratory long-term filtration (LTF) tests. Upon completion of the LTF tests, particle size analyses, permittivity tests, piping measurements, and image analyses were conducted to evaluate clogging and retention performances. When the clogging ratios and piping measurements were considered, all compost-geotextile combinations yielded acceptable clogging and retention performance. A parametric study was conducted to determine if different characteristic pore sizes and grain sizes influenced the laboratory clogging ratios and showed no apparent relationship. Existing filter selection criteria successfully predicted the observed retention behavior but failed to predict the clogging behavior. Based on limited LTF data, compost is not likely to promote clogging in geotextiles; however, additional soil-geotextile filtration tests are necessary to propose a new filter criterion for clogging.