Oxidant Transport for ISCO Treatment Using Electric Gradients: A Research Overview

摘要

Significant challenges remain in remediating low-permeability porous media (e.g. clays, silts) contaminated with organic contaminants. Current remediation technologies such as in-situ chemical oxidation (ISCO) are often ineffective, with treatment limited by very slow rates of groundwater advection and molecular diffusion. Previous studies indicated that electrokinetic transport (EK), as induced by electric field application, increased transport rates of charged solutes through low-permeability sediments. Research into utilising EK to deliver oxidants (EK-ISCO) was conducted by the University of Western Australia and Golder Associates as an ARC Linkage project. In laboratory tests, application of direct current resulted in permanganate transport within clay, however this stalled after some time. A specially-designed experimental apparatus showed that stalling could be mitigated by controlling the electrode reservoir pH, resulting in breakthrough of permanganate through the clay. Experiments assessing persulfate transport via EK-ISCO through dichloroethane contaminated peat found that transport was inhibited by natural oxidant demand. This was found to be a key factor for determining persulfate dosage. A numerical model was developed that simulates groundwater flow and multi-species reactive transport under both hydraulic and electric gradients. Modelling and experimental studies evaluated different strategies for field implementation. The technology is currently being trialled to deliver bioremediation agents and oxidants in North America and Europe.