Lead University: Lehigh University
PI: Derick G. Brown, Department of Civil and Environmental Engineering
Co-PI(s): John T. Fox, Department of Civil and Environmental Engineering
PA Industry: Evoqua Water Technologies

Granular activated carbon (GAC) is a hydrophobic material that has a very high surface area to volume ratio, and because of these properties, it is routinely used to remove contaminants from water through the process of sorption. GAC systems are ubiquitous in water treatment, and common applications include small-scale household water treatment filters, large-scale municipal water treatment plants, and specialty high-purity water sytesms for manufacturing and scientific applications. One concern with GAC is that it can serve as a solid surface for the growth of bacterial biofilms. These biofilms may add benefit to the treatment of the water, as is the case with fluidized-bed bioreactors, or they can be a detriment, as is the case when using GAC for treatment of drinking water. For this latter case, GAC exhibiting antimicrobial properties is desirable; as long as the active antimicrobial components don’t themselves act as a contaminant to the system. Unfortunately, there is limited data on the innate antimicrobial properties of activated carbon. While there have been efforts focused on impregnating antimicrobial chemicals, such as silver, into the GAC, these GACs are not favorable for drinking water treatment due to leaching of the antimicrobial chemicals into the water. As such, there remains a demonstrated need to develop a passively-antimicrobial GAC that does not impact the water quality.

Evoqua Water Technologies and Lehigh University has initiated a collaboration to address this issue and develop a passive antimicrobial GAC. This collaboration combines Evoqua's activated carbon expertise and manufacturing capabilities with Lehigh's expertise in environmental biotechnology. The basis for this current effort is a hypothesis developed at Lehigh that describes how the addition of certain acid/base functional groups on a surface can result in a passive surface with antimicrobial properties. Using simple batch respirometer experiments, our team has demonstrated that GAC modified with weak- and strong-base functional groups shows promise to reduce bacterial colonization and biofilm formation on the GAC surface. The work proposed herein will move the system to the pilot-scale with the goal of demonstrating reduced bacterial colonization in long-term GAC flow-through columns. This project strengthens the collaborative effort between Evoqua and Lehigh University and will lead to a validated scientific framework for producing antimicrobial activated carbon.