ERT monitoring of environmental remediation processes

• Published in: Measurement science & technology Vol. 7; no. 3; pp. 375 - 383
• Main Authors: LaBrecque, D J, Ramirez, A L, Daily, W D, Binley, A M, Schima, S A
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.03.1996
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/7/3/019

An overview is given of electrical resistance tomography (ERT), including survey design and data interpretation. The technique was used to evaluate 3 case studies of remediation, which utilized electrical resistance (Joule) heating of clay layers, air sparging or electrokinetic treatment. Joule heating was successfully applied to a clay zone contaminated with trichloroethane (TCE) and perchloroethane (PCE) resulting in removal of 475 kg of PCE and 107 kg of TCE during the test. ERT imaging showed that conductivity increased initially due to temperature elevation, with conductivity falling later as the clay was dehydrated. In the case study which utilized air sparging, air was injected into a sandy aquifer and ERT images clearly showed temporal changes in air saturation. Electrokinetic treatment involving ion transport in an electric current was applied to core samples in a laboratory test and the process monitored by ERT. The treatment created a considerable change in core resistivity which decreased near the anode and increased near the cathode. The field experiments, while successful, did not proceed entirely as expected and ERT provided an understanding of movements of air, fluids, ions and heat, which could be applied to improvements in remediation system design.