Oregon State University scientists have created new gellan gum-based hydrogel beads to clean up contaminated groundwater in a maintenance-free and long-lasting manner.
Among the contaminants addressed in the study are 1,1,1-trichloroethane, cis-1,2-dichloroethene, and 1,4-dioxane – all degreasers commonly used by industry and the military.
These chemicals are known to infiltrate groundwater through leaky underground storage tanks or runoff, or by simply being dumped on the ground as they were in past.
The new decontamination method – a collaboration between OSU and NC State – works because the microbes produce an enzyme that oxidizes the toxins when groundwater contaminants diffuse into the beads.
The result is a transformation of the contaminants into harmless compounds.
“We’ve created a process called long-term aerobic cometabolism, which is an enclosed, passive, self-sustaining system for groundwater remediation,” says OSU distinguished professor Lew Semprini.
“The beauty of this is that everything happens inside the beads.”
“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,” says Semprini.
“To my knowledge, this is the first time it’s been done.”
Semprini and his team co-encapsulated the bacteria culture Rhodococcus rhodochrous and a slow-release growth substrate within the hydrogel beads that they produced in the lab.
As groundwater flows by the beads, the contaminants diffuse into the beads, where the slow release substrate reacts with groundwater to produce alcohol that sustains the Rhodococcus bacteria.
The bacteria contain a monooxygenase enzyme that transforms the contaminants into harmless compounds, including carbon dioxide, water and chloride ions.
The purified water and the byproducts then diffuse out of the beads and rejoin the groundwater plume.
According to the scientists, the beads were found to remove more than 99% of the contaminants, and their concentrations declined from several hundred parts per billion to less than 1 part per billion.
Image and content: Oregon State University