Electrokinetic movement and biodegradation of 2,4‐dichlorophenoxyacetic acid in silt soil

Abstract

The coupling of electrokinetic movement of an organic contaminant, 2,4-dichlorophenoxyacetic acid (2,4-D), through soil and its biodegradation in situ has been demonstrated. In a first experiment, the direction and rate of movement of 2,4-D were determined using homogeneously contaminated soil (864 mg 2,4-D/kg dry weight soil) compacted into six individual compartments, 6 cm long, 3 cm wide, and 4 cm deep. Each compartment was bordered by a carbon felt anode and a stainless steel cathode. The application of a current density of 3.72 A/m(2) led to migration of 2,4-D towards the anode at a rate of approximately 4 cm/day. In a second experiment, electrokinetic movement and biodegradation were combined in situ. Sterilized silt soil contaminated with ring-labeled 14C-2,4-D (811 mg 2,4-D/kg dry weight soil) was compacted into a single soil compartment, 22 cm long, 7 cm wide, and 4 cm deep, in a 4.5 cm region adjacent to the cathode. The remainder of the compartment was filled with sterilized soil (to a total weight of 1,015 g). Burkholderia spp. RASC c2 (1.88 x 10(11) cells), a tetracycline-resistant bacterium with chromosomally encoded degradative genes for 2,4-D, was inoculated into the soil at a position 14-16 cm from the cathode. The reactor was placed within a sealed perspex box, with a constant air flow connected to sodium hydroxide traps. Under an applied current density of 0.89 A/m(2), the pollutant moved towards the bacteria. As it reached the inoculated region, its concentration decreased in the soil and 14CO2 was recovered in the traps. At the end of the experiment, 87.1% of radiolabel had been removed from the soil, 5.8% of which was recovered as 14CO2. A third, control, experiment showed a significant contrast in the absence of an electric current, where a slow rate of diffusion controlled the movement of both 2,4-D and bacteria in the soil and biodegradation occurred at the interface between the diffusing fronts.

Effect of Direct Electric Current on the Cell Surface Properties of Phenol-Degrading Bacteria

“…This should favor the detachment of bacteria from negatively charged particles of soils and the electrophoretic movement in the subsurface (11,12,15). However, considering the harmful effect discussed above, a current of more than 20 mA does not seem to be suitable for practical applications for injection and transport of phenol-degrading bacteria for the purpose of bioaugmentation.…”

“…The extracellular substances and cell shape were also examined due to their substantial influence on bacterial mobility in the subsurface (18,21). Our interest in these traits was derived from the potential for using DC to transport and mix bacterial inoculants for bioaugmentation (4,7,11,12,15).…”

Effect of polarity-reversal on electrokinetic enhanced bioremediation of Pyrene contaminated soil

“…EK can be used particularly effectively in fine grained soils of low hydraulic conductivity, which is different from other in-situ methods [7]. Several studies have shown that EK-Bio was effective for remediation of PAHs in clayey soil [8][9][10]. When direct current (DC) electric fields were applied to contaminated soil via electrodes placed into the ground, electrolysis occurred between the anode and the cathode.…”

On-site and in situ remediation technologies applicable to petroleum hydrocarbon contaminated sites in the Antarctic and Arctic

“…Technology coupling may also be required at highly heterogeneous sites, that is, characterized by variable subsurface flow rates, soil types or an uneven distribution of contamination (Filler et al 2006;Camenzuli et al 2013). Therefore, it is essential to develop an understanding of the capability of each technology for use independently or for coupled use by either simultaneous application or as a component in a treatment train (Jackman et al 2001;Cang et al 2011;Camenzuli et al 2013).…”