Converting Contaminated Aquifers into Purifying Filters: Colloidal Activated Carbon
Recent innovations in dispersion chemistry has resulted in the development of a highly sorbent, colloidal activated carbon which has been demonstrated to flow easily into aquifer matrices. Once distributed in the subsurface, the colloidal material will permanently deposit to form a coating on the aquifer matrix while leaving groundwater flow unrestricted. Dissolved contaminants rapidly sorb into the activated carbon and are stripped from groundwater fluxing through the treated zone or back-diffusing from lower permeability zones. Biodegradation of the contaminants concentrated upon the carbon layer is accelerated by the use of dispersion chemistry that serves as long term electron donor and the option of bioaugmenting with contaminant-degrading microbial consortia (e.g. DHC).
Data is presented from a dual-porosity tank study conducted at Colorado State University which supports the hypothesis that colloidal activated carbon, when applied in high flux zones, is highly effective at the long-term treatment of back-diffusion. Key data from this study includes the observation of limited daughter product formation in conjunction with Dehalococcoides populations that are two orders of magnitude higher in the presence of the colloidal activated carbon than without. Additional data is also included on the ability of the colloidal carbon to migrate throughout both the transmissive and the lower permeability soil layers.
Results of pilot-scale and full-scale commercial remediation projects are also presented which indicate that colloidal activated carbon may be an effective solution in treating back-diffusing legacy plumes. Technical hurdles to success are described and future development plans are discussed.