Can electro-bioremediation of polluted soils perform as a self-sustainable process?

Abstract

This work studies the effect of treatment period on remediation efficiency in an oxyfluorfen-polluted soil through electro-bioremediation technology. Five lab-scale experimental plants were started up simultaneously, operated under an electric field of 1.0 V cm−1 with a polarity reversal frequency of 2 day−1 and disconnected at different times (2, 4, 6, 11 and 24 weeks); these plants underwent post mortem characterization after their operation period. Various parameters were monitored in the electrolyte wells during the experiments. The obtained results indicate that despite the low reproducibility of pH and conductivity in the wells (not in soil), the main conclusions that can be drawn for the different plants are sound and hence have acceptable reproducibility. Polarity reversal allowed suitable conditions for microbial life in terms of pH, but nutrients were also depleted in the soil, which leads to a decrease in the total population of microorganisms during treatment. For treatment periods of less than 10 weeks, there was an appreciable population of microorganisms in the soil, which reached oxyfluorfen removal levels of up to 40%. Longer reaction times were ineffective, and this was related to the much lower concentration of microorganisms. In comparing these results to those obtained in conventional soil bioremediation technology, the application of polarity-reversed electric current led to an increase in the average removal of oxyfluorfen from 0.11 to 0.17 mg kg−1 day−1 but a much higher decrease in the active microorganism population from 88.0 ± 9.0 to 41.0 ± 6.0% of the initial seeded value.