Researchers at Oregon State University (OSU) and North Carolina State University have discovered that beads containing a combination of bacteria and a slow-release food supply can help clean up contaminated groundwater. The researchers used hydrogel beads; hydrogel is made with an ingredient found in processed food and is an absorbent polymeric network that has many applications. Researchers are looking at hydrogel beads as being useful for cleaning groundwater containing dangerous compounds, many of which the Centers for Disease Control (CDC) consider to be human carcinogens. The study, which was funded by the Department of Defense (DOD), is published in Environmental Science: Processes & Impacts.
The study specifically addresses several contaminants, which are used as degreasers: 1,1,1-trichloroethane, cis-1,2-dichloroethene, and 1,4-dioxane. The decontamination method that the researchers developed involves the hydrogel beads absorbing and oxidizing the toxic compounds, rendering them harmless.
According to the principal researcher and professor of environmental engineering at OSU, Lew Semprini, “We've created a process called long-term aerobic cometabolism, which is an enclosed, passive, self-sustaining system for groundwater remediation. The beauty of this is that everything happens inside the beads."
Before this discovery, the practice was to add propane or methane to the subsurface of the water. Those substrates would cause microbes to produce enzymes that would make the contaminants non-toxic. The problem was that these substrates often end up competing for enzymes, meaning that not all toxins were decontaminated. The new system that the researchers developed doesn’t have that issue. Says Semprini, “We've flipped the paradigm on its head by putting the right microorganism inside hydrogel beads and supplying it with a slow-release food source.”
Semprini found that the hydrogel beads can remove more than 99% of the contaminants, significantly decreasing the concentrations of the toxins. The system is dependent on how long the bacteria in the beads can live, which is based on how long the growth substrate lasts. "It's a question for future research," Semprini said. "How do we make beads that last many years, or how do we develop systems that can easily be replaced?” Everybody favors sustainability in this type of system: Can we just have something working in the subsurface without much maintenance?", Semprini continued. "I think we've achieved that."