Sustained In Situ Chemical Oxidation (ISCO) of 1,4-Dioxane Using Slow Release Chemical Oxidant Cylinders

Dr. Patrick Evans | CDM Smith



The objective of this project is to demonstrate use of slow-release chemical oxidant candles to treat large dilute plumes of dioxane in situ. Permanganate and unactivated persulfate are capable of oxidizing dioxane albeit at low rates. Specific technical objectives of this demonstration/validation project are to:

  • Demonstrate the use of permanganate and unactivated persulfate in the slow-release candles to couple the oxidant release rate, the dioxane transport rate, and the dioxane destruction rate.
  • Demonstrate that the slow-release candle delivery vehicle can minimize potential secondary effects such as metals mobilization and permeability reduction.
  • Produce engineering guidance in the form of a practical spreadsheet tool.

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Technology Description

Slow-release candles are an excellent fit for large, dilute dioxane plumes because: (1) the slow-release feature is compatible with the low reaction rates; (2) the slow-release feature can be used to intercept plumes in a permeable reactive barrier (PRB) or funnel and gate (F&G); and (3) the technology is less expensive than conventional pump and treat with advanced oxidation. The approach is also versatile. It is applicable to an array of geology/geochemistry settings – the appropriate oxidant can be selected based on geology and geochemistry. This flexibility allows for system design that matches oxidant release rate, the dioxane transport rate, and the dioxane oxidation rate. Different formulations are possible (candles, chunks, etc.) as well as different delivery approaches (inwell, direct push, etc.).

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Slow-release candles provide a unique and versatile delivery vehicle that is modular, can leverage existing monitoring wells, and matches the rate of contaminant destruction to the rate of contaminant transport. This new, low-cost passive in situ technology for dioxane and other co-contaminants is applicable to large dilute plumes and can be used in heterogeneous aquifers It can be implemented in a variety of configurations with different oxidants. (Anticipated Project Completion - 2018)

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Points of Contact

Principal Investigator

Dr. Patrick Evans

CDM Smith

Phone: 206-351-0228

Program Manager

Environmental Restoration