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Sarah Gustitus-Graham

University of Virginia, Ph.D.
EREF Scholar 2017

Determining the Service Life of Bentonite-Polymer Geosynthetic Clay Liners Permeated with Aggressive LeachatesProject Description:
The goal of Sarah’s research is to develop new techniques to predict the service life of geosynthetic clay liners (GCLs) produced with bentonite-polymer composites. GCLs are composed of a layer of clay sandwiched between two geotextiles, which create a low hydraulic conductivity barrier to prevent landfill leachate from contaminating native soil and groundwater. Historically, sodium bentonite has been the primary clay used in the production of GCLs; however, sodium bentonite may be adversely affected by aggressive leachates, such as leachates with high ionic strength of an abundance of polyvalent cations. Therefore, researchers have sought ways to modify bentonite in order to reduce its susceptibility to extreme leachates so that liner integrity can be maintained, even in adverse conditions.

One way to enhance bentonite’s resistance to extreme leachates is to modify it by incorporating a polymer. Bentonite-polymer geosynthetic clay liners (B-P GCLs) have been shown to maintain low hydraulic conductivities, even in the presence of high pH or high ionic strength leachates that increase the hydraulic conductivity of traditional sodium bentonite GCLs. The endurance of B-P GCLs has made them desirable for use in industries such as coal-fired power production, mining or aluminum beneficiation, which produce more aggressive leachates.

Aggressive leachates can cause severe environmental effects; therefore, for several industry applications, it is necessary that B-P GCLs maintain low hydraulic conductivity for extended periods of time. However, over time the polymer within B-P GCLs may be eluted or degraded within the liner, and the time-scale over which this happens is unclear, making it difficult to estimate the service life expectancy of B-P GCLs.

The objective of this research is to develop and implement an accelerated test protocol which utilizes elevated temperature test conditions and Arrhenius modeling to predict the service life of B-P GCLs used with different waste streams. Throughout this testing, the evolution of the quality of both the B-P GCL and the leachate effluent will be monitored in order to understand how the polymer within the composite migrates or degrades over time, and what effect this has on the hydraulic conductivity of the liner and the chemistry of the leachate. Through this effort, guidance will be developed for industries that have a need for durable liners so that they may determine to what extent B-P GCLs may be effective for their applications.

Sarah began her doctoral studies in Civil and Environmental Engineering in 2017 at the University of Virginia, where she is researching the service life expectancy of bentonite-polymer composite geosynthetic clay liners. She obtained a B.S. in Environmental Engineering from the University of Florida in 2015, and an M.S. in Civil Engineering from Auburn University in 2017. Sarah’s first introduction to the solid waste management field was during a co-op rotation at Ascend Performance Materials, where she gained experience analyzing leachate data from the plant’s onsite landfill. Following this experience, she furthered her interest in solid waste management through working on a waste composition study at the University of Florida. Most recently, she spent the summer interning with Geosyntec Consultants, where she assisted on several landfill design projects, most of which were focused on the disposal of coal combustion residuals generated during electricity production.