Innovation lifts limits of landfill liners

Posted on 27. Sep, 2013 by in Academic Departments, Annual Report, Civil and Environmental Engineering, Economic Impact, Environment and Sustainability, Issues, Research

Generally made from bentonite clay sandwiched between textile or membrane layers, geosynthetic clay liners are the “gold standard” for preventing industrial, hazardous and municipal solid wastes from seeping into the environment. Such liners are particularly effective barriers, because as the clay absorbs water, it swells and the pore spaces between its particles shrink.

Yet, even these high-performing liners can’t contain everything. “Over approximately the past decade, university research—with UW-Madison leading the way—has shown that certain chemistries can negatively impact the hydraulic performance of bentonite-based liners,” says Chris Athanassopoulos, technical services manager with environmental solutions company CETCO. “These limitations could prevent the use of these liners in important emerging markets.”

Take, for example, red mud, a toxic byproduct of the process for refining bauxite ore to produce aluminum oxide. Because it is highly alkaline, red mud can dissolve even geosynthetic clay barriers used to contain low-level radioactive waste.

Rather than fight that high pH, however, CETCO began an effort to engineer polymer-based bentonite clays that would work with it. Essentially, the company has amended its clay with polymer molecules that ride the liquid waste through the clay and fill its pores. “We’ve got large molecules clogging the large pores. They’re really resilient and aren’t degraded by the chemicals flowing through the barrier,” says Wisconsin Distinguished Professor of Civil and Environmental Engineering and Geological Engineering Craig Benson, who is working with CETCO to study the mechanisms underlying this process. “We’ve never made anything more impervious. It’s blown all the other products away.”

Benson tested and confirmed the material’s long-term performance in contact with leachates known to be problematic for standard bentonite. “Data from a well-known, well-respected independent industry expert was valuable in gaining acceptance from engineers, owners and regulators,” says Athanassopoulos. “This year, we are seeing the new products gain some traction, with important project wins in North America and overseas.”

He says the company’s long-standing partnership with UW-Madison has been mutually beneficial. “In working together to study the limitations of traditional liner systems with high-strength wastes, and the potential application of polymer-modified clays, there has been a healthy exchange of information between our company and the university, with both sides learning and benefiting,” he says.Bucky Badger head

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