Gary Birk is the founder and Managing Partner for Tersus Environmental. He has a bachelor's degree in chemical engineering from North Carolina State University and holds registrations as a Professional Engineer in North Carolina, Virginia and Florida. Well-known for his contributions to in situ anaerobic groundwater remediation, he has worked on over 200 enhanced reductive dechlorination projects in North America, Europe, Asia and Africa.
His focus is on engaging cutting-edge sustainable green technologies that help environmental consulting companies restore or remediate groundwater and soil at challenging sites associated with Fortune 500 companies, the U.S. Departments of Energy and Defense, and NASA. Gary has worked extensively in the field of bioremediation and environmental consulting on soil and groundwater assessments and cleanups. His experience includes two decades as an environmental contractor and consultant focused on project management of multiphase, multidisciplinary environmental design and construction projects, predominantly for industry and utilities. Gary has authored Design Tools for in situ bioremediation that have advanced the state-of-the-practice in estimating substrate application rates. Gary's current focus is on remediation of emerging contaminants such as Per- and Polyfluoroalkyl Substances (PFAS).
Ex Situ Treatments of Aqueous Film-Forming Foam Impacted Water
Per- and Polyfluoroalkyl Substances (PFASs) are surfactants and polymers that are widely distributed across the higher trophic levels and are found in air, soil and groundwater at sites across the U.S. Surfactant applications used heavily in the military include aqueous film-forming foams (AFFFs) used to extinguish fires involving highly flammable liquids. The toxicity, mobility and bioaccumulation potential of PFASs pose potential adverse effects for the environment and human health.
PFASs are fluorinated organic compounds in which the hydrogen atoms of the hydrocarbon skeleton are substituted fully by fluorine atoms. For this reason, they among the strongest organic compounds and thus considered non-degradable because they persist for a long time in the environment.
Practitioners have difficulty remediating these compounds at a reasonable cost because PFASs tend to be highly soluble, do not favorably partition into the vapor phase, and do not adsorb well to granular activated carbon (GAC). To date, adsorption on activated carbon was the only technically feasible method to treat PFAS-contaminated water. The presentation will provide updates on a novel treatment train approach to address ex situ treatment of AFFF impacted water.
In the pretreatment phase, PFASs are precipitated by metering the liquid surface active compound into a stirring tank. The amount of reagent can be adjusted to varying concentrations. The precipitation products are separated from the water as micro-flocks by simple processes such as sedimentation and filtration. The precipitants can be concentrated to a very high degree, which allows for very economical disposal as compared to GAC. Posttreatment of the remaining residual contaminants is performed by a downstream activated carbon and activated carbon / aluminum hydroxide / Kaolin filter. Due to the significant reduction in the PFAS-contaminated water in the initial precipitation stage (up to 90%), the PFAS contaminant load reaching the absorbent filter(s) is lowered, which leads to a significant extension of the adsorber's lifetime, again significantly lowering operating costs.
The presentation will also provide results of the effectiveness of an activated carbon / aluminum hydroxide / Kaolin mixture to treat PFASs. Studies have concluded that the adsorption capacity of the mixture for the smaller chain fluorinated substances PFBA and PFBS is vastly superior to that of GAC. This is likely due to the presence of the noncarbon components within the mixture creating unique physical chemical interactions with the smaller chain PFAS compounds.