Optimization of Polymer-Amended Fly Ash and Paper Pulp Millings Mixture for Alternative Landfill Liner

摘要

In 2012 the City of Flagstaff partnered with researchers at the Dept. of Civil and Environmental Engineering at Northern Arizona University to successfully develop a mix design utilizing sludge derived from the manufacturing of recycled paper pulp sludge (PPS) and fly ash as a component of a landfill cap. This research has been extended to explore the addition of polymers to the mix of waste materials in order to optimize a design that would be suitable as a component for an EPA Subtitle D-approvable landfill liner. Cinder Lake Landfill (CLL) serves several communities in Northern Arizona and is managed by the City of Flagstaff. CLL does not have a reliable source of clay needed to construct a required landfill liner, which is necessary for the upcoming 108-acre landfill expansion. However, CLL receives approximately 80 tons of recycled PPS daily from the local tissue manufacturing plant. PPS is currently used as daily cover and was tested for use as part of a landfill cap, as noted above. Incorporating polymers in alternative materials such as PPS and fly ash has the potential to meet performance criteria and be approved by state and federal regulators, and has the potential to save the City millions of dollars over conventional composite liners of geomembrane and clay. Different mixtures of PPS, fly ash and three different polymers are currently being subjected to testing for the following: Water Content, Specific Gravity, Porosity, Organic Content, Atterberg Limits (plasticity), Proctor Compaction, Consolidation, California Bearing Ratio, Shear Strength, Gas Permeability, and Liquid Permeability. The optimal mixture of PPS and fly ash will be blended with a range of polymer concentrations. The goal is to find an optimal mix of PPS, fly ash, and polymer to achieve regulatory standards related to permeability, along with other desirable properties such as strength and flexibility. The optimum mixture(s) will then be subjected to field trials, scheduled to begin in 2016, in which test cells will be created at CLL, The liner will be constructed with the optimized mixture(s), and the cells will be operated as landfills for 1-2 years. Results from lab and field testing will be submitted to federal and state regulators for consideration as an alternative liner approach.