Bioelectrochemically-assisted remediationa novel strategy for cleaning-up polluted soils

Abstract

Bioelectrochemically-assisted remediation is a novel tool for enhancing the degradation of soil pollutants. This application derives from the Sediment Microbial Fuel Cell (SMFC) concept, where an anode is buried in an anaerobic soil and connected through an electrical circuit to a cathode in the overlying water layer. The novelty of this technique lies in the unlimited character of soil-buried electrode as terminal electron acceptor (anode) allowing microorganisms to perform oxidative metabolism beyond the natural conditions found in soil. Unlike most of the standard Microbial Fuel Cells (MFCs) application developed in water matrix, implementing SMFC in the soil implies a very high resistance for proton transfer that limits the mass transfer, decreasing the efficiency in the degradation process. This is probably the reason why, since 2001, SMFC systems have been developed in ecological water bodies as marine sediments or freshwater flooded environments (rivers and waterlogged field crops), where saturated soil condition facilitates the ions transfer across soil matrix. However, this water dependence limits the application of microbial electrochemistry in soil because flooding is not a common situation for soil environments. The aim of this thesis was to evaluate the application of microbial electrochemical systems in soil for either harvesting energy or bioremediating polluted soils. In this context, bioremediation assays were based on the use of he herbicide atrazine as model compound. The remarkable impact of electrodes on soil bioremediation suggests a promising future for this emerging environmental technology. The work presented in this thesis supports the idea that this novel strategy for cleaning-up polluted soil might represent a potential alternative to conventional bioremediating techniques. This novel research field shows a wide spectrum of possibilities for its future application in real environments.