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Polyphosphate injection to immobilize contaminants

Diagram of long-chain polyphosphate injection for contaminant immobilization in deep aquifers
Injection of long-chain polyphosphate to immobilize contaminants in deep aquifers.

Apatite barriers are an effective remediation strategy to immobilize contaminants in a migrating plume, but such a barrier approach cannot effectively remediate pore-water contamination situated in deep aquifers or under conditions such as those found in the Hanford Site vadose zone (which can extend to a depth of 300 feet).  For such situations, an alternate strategy is injection of water-soluble phosphate compounds into the plume via strategically placed wells.

PNNL researchers are testing the characteristics of soluble, long-chain polyphosphate materials that have demonstrated a delay in the precipitation of phosphate phases that would alter hydraulic conductivity.  Bench-scale and intermediate-scale studies will characterize the chemistry and kinetics of polyphosphate interactions with the contaminant matrix and the formation, leading to a pilot-scale treatability test and subsequent performance assessment.  This remediation strategy should find many applications in deep-aquifer and deep-vadose-zone contaminant plumes.

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