Formatted Title
Beyond the Barrier: Long-Term Performance of Multiple Colloidal Activated Carbon Permeable Reactive Barrier Sites
Background/Objectives
Background/Objectives. Successful applications to treat dissolved phase contaminant plumes in situ have been completed using colloidal active carbon (CAC) since 2014. Remedial solutions incorporating CAC are a rapidly growing segment of the environmental industry. Treatments often take the form of a single or multiple permeable reactive barrier (PRB) systems which work with natural groundwater flux to remove contaminants passing through the PRB. In the case of chlorinated ethenes, these contaminants are typically destroyed via anaerobic bioremediation or abiotic destruction. Long-term monitoring provides valuable performance data that can improve our understanding of plume cleanup using CAC technology. For example, the effects of back diffusion can often be measured and better understood through long-term data sets.
Approach/Activities
Approach/Activities. Monitoring data from multiple, extensively studied sites with data collected over a period of about five years will be presented. The data will demonstrate the cleanup of the plumes down gradient of the activated carbon barriers. This will include data from performance monitoring wells located within the PRB as well as at various distances ranging up to 200 feet down-gradient of the treatment barrier array. The interplay between the plume migration, groundwater velocity, back diffusion, and the rate of plume cleanup will be explored. The presentation will also examine the quantities of groundwater treated by the barriers over time using directly measured contaminant mass flux to estimate the quantity of contaminant mass captured and treated by the barriers.
Results/Lessons Learned
Results/Lessons Learned. Evidence demonstrates that CAC barriers can represent a highly effective, efficient, and long-lasting means to treat a variety of contaminants across a range of geologic settings. Having a thorough understanding of the amount of stored matrix mass, rate of back diffusion, and groundwater velocity enables the cleanup timeline down-gradient of a CAC barrier to be determined.