David Alden is a Technical Associate with Tersus Environmental where he provides technical support for Tersus' portfolio of biotechnology-based solutions to manage complex, challenging environmental liabilities and reduce costs for site closure. He is a graduate of Universidad de las Americas-Puebla, Mexico, where he majored in Civil Engineering with a focus on waste-water treatment and and holds registration as a Professional Engineer in North Carolina. Alden worked for 4 years in the upstream oilfield sector performing offshore well tests and completion design and installation in the Gulf of Mexico. He participated in the in-situ oil-shale extraction experiment in the Piceance Basin, in Northwestern Colorado where protecting groundwater was the main challenge. Alden recently specialized in groundwater studies, completing a Masters Degree program in Joseph Fourier University, Grenoble France.
ALTERNATE PLATFORM PRESENTER - NAPL Characterization and Depletion: My Old Friend
Innovative Surfactant System Formulations for LNAPL Recovery
Background/Objectives. Based mostly on empirical experience, practitioners have concluded that NAPL solubilization was a necessary first step in the mobilization process and that surfactant concentration, up to a point, was generally proportional to performance. It is now understood, as evidenced by trends seen in the detergent industry that high efficiency products at lower concentrations meet the industry's requirements. These lower concentration formulations are not only as effective but work well at a variety of temperatures and water hardness conditions. That said, surfactants typically found in household cleaning systems, such as laundry detergent or shampoo, lower the interfacial tension (IFT) by about an order of magnitude. This is sufficient because mechanical energy can be added to laundry or shampooing to mobilize the trapped oil. In a porous medium, however, we must reduce the IFT by three or four orders of magnitude to reach our goals.
Approach/Activities. Technology developed at the University of Oklahoma, originally focused for enhanced oil recovery at petroleum reservoirs and subsequently adapted to the environmental arena, can lower the IFT sufficiently to allow physical mobilization of residual LNAPL with the limited production of thermodynamically stable emulsions. This talk will focus on the use of artfully formulated surfactant blends that reduce solubilization and simply allow LNAPLs in saturated soils to become mobile.
Results/Lessons learned. The presentation will include results and lessons learned from the latest field implementation where selecting an optimized surfactant blend minimized required flush water and costs for produced effluent fluids treatment.
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. They are persistent in the environment, among the strongest organic compounds and thus considered non-degradable. 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, GAC has been the only technically feasible method to treat PFAS-aqueous media. This presentation will present a treatment train for ex situ treatments of Aqueous Film-Forming Foam 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 absorber's lifetime, again significantly lowering operating costs. The presentation will also provide results of the effectiveness of an activated carbon / aluminum hydroxide / K