DATE: Centennial Symposium
Environmental Research: The Next 100 Years
Friday, October 30, 2020 TIME: 2:30 pm PLACE: ,
Clemson University, Department of Environmental Engineering & Earth Sciences, Department of Microbiology
Novel Electron Donors and New Uses for "Old" Activated Carbon: the changing face of in situ (bio)remediation
Topic: metal reducing microbes in the environment
In situ activated carbon is a unique field adaptation of a classic ex situ water treatment strategy. Instead of pumping water out of the ground and adsorbing contaminants on activated carbon units that are above ground, the activated carbon is forcefully injected into the aquifer material and distributed in situ. The adsorption part of the technology is undisputed – we know that contaminants like trichloroethylene (TCE) will adsorb to activated carbon. What we do not know is what happens next. The vendors of the material aggressively advertise that microbial degradation will increase because activated carbon promotes biofilms; however, these are advertisements without any data to back them up. Our data suggest the TCE reduction is actually inhibited by activated carbon, because TCE and its daughter product cis-dichloroethylene have mass transfer issues between the carbon and the aqueous phase, which limit microbial reduction. Alternatively, nitrated explosives – for which in situ activated carbon has not been reported – are readily degraded once sorbed to activated carbon. Perhaps the practitioners are looking at the wrong contaminants.
Lipid electron donors are pervasive in bioremediation because they are marketed as "long term, slow release", which means they only have to be added once, and then the stakeholders can just monitor the activity. The problem rests with the fact that many microbial populations do not readily oxidize lipids during respiration, or fermentation. We have developed a novel electron donor approach using rendered animal co-products, which are functionally an unused waste of the food industry. Our data indicate that these protein-lipid-nutrient combinations are better than soybean oil (lipid only) based electron donors. And, they are fractions of the cost of soybean oil-based electron donors.
I will discuss new developments in (bio)remediation, and how we can develop new technologies while improving those already in use.
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