The application of an electric field to contaminated soil specimens and the resulting electrokinetic phenomena have been combined with the degradative actions of bacteria to create a novel method for the remediation of contaminated land.
Currently, the vast majority of remediation projects involve disposing of contaminated soil in landfill. With the introduction of, and increases in, landfill tax in the UK, this option is becoming less desirable, and so robust, more sustainable techniques are required, such as bioremediation.
A major problem with the implementation of bioremediation is the bioavailability of contaminating chemicals. Reduced accessibility of bacteria to the chemical(s) they are attempting to degrade can lead to significant increases in required remediation times, as well as the possibility of significant residual contamination, the levels of which cannot be easily further reduced.
This thesis addresses the problem of bioavailability of contaminants in soils, and has investigated the use of electrokinetic phenomena as tools to bring about an increase in this factor, leading to improved biodegradation. Soil contaminated with pentachlorophenol (sodium salt) was subjected to an electric field in a number of experiments, with significant transport of the initially ionic chemical noted.
The transport and fate of this chemical were tracked throughout each experiment, along with properties of the soil pore fluid. Significant changes in soil chemistry were noted (particularly pH or moisture content, depending on the experiment). The effect of pH change was found to be particularly important in this respect, with acidic conditions hindering both movement and bio availability.
A method of applying an electric field to contaminated soil containing degrading bacteria was developed which minimised the changes to these parameters within the soil. A significant increase in the effectiveness of the remediation was noted with this technique, with substantially faster degradation found to occur.
Source: University of Oxford
Author: Michael John Harbottle