Formatted Title
2023 Update: The Transition to Colloidal Solids with Further Optimization through Fully Automated Injection Systems
Background/Objectives
For years, practitioners have been injecting micro-scale solids for remediation of solvents, petroleum, pesticides, and metals. This has challenged field applications since these solids have to be distributed through new preferential pathways created for their distribution. For finer grained soils, this is still considered best practice and widely applied across the industry. However, for coarse grained soils, distribution has been challenging. By moving towards a colloidal size solid, like activated carbon or ZVI, more effective distribution in transmissive zones can be accomplished which can result in more effective remediation when targeting contaminant flux coming off source areas. However, it's not just the chemistry alone, but the delivery of these colloidal chemistries into groundwater that is required to make these chemistries work as designed.
Approach/Activities
To effectively treat transmissive zones, the persistence of microscale solids like ZVI and activated carbon is well understood and their delivery through smaller particle sizes (colloidal) has made it possible to better distribute these chemistries into these target zones. However, injection technology has not advanced in the last 20 years beyond ball valves, analog pressure gauges, and mechanical or turbine flow meters. During this time, research and empirical evidence has mounted confirming that distribution and contact of in situ chemistries is a key success factor that has only recently received the attention that it deserved versus the primary focus on chemistry and contaminant efficacy.
As a result, colloidal solids can be effectively distributed through these transmissive zones because they can flow through the soil pore throats. The controllability of existing injection technology is not precise enough to ensure that distribution does not also occur through newly created flow paths by exceeding the fracture pressure of these target intervals. Automation which can set precise shutdown or control setpoints ensures optimal injection performance. Considering the large life cycle costs of remediation and the investment made in characterization and design, it only makes sense that the correct physical form of chemistry and its injection approach be optimized.
Results/Lessons Learned
Cascade will present a 2023 update on injection projects utilizing automated injection system (called Pathfinder) along with digital injection logs from nine projects (East and West coasts) completed 2021 through 2023. The basis for injection pressure and flow control parameters as it relates to site lithology of injection target intervals will also be presented.