Degradation of perchloroethylene and dichlorophenol by pulsed-electric discharge and bioremediation

Abstract

Pulsed electric discharge (PED) and bioremediation were combined to create a novel two-stage system which dechlorinates the halogenated pollutants, 2,4dichlorophenol and perchloroethylene, with repetitive (0.1-1 kHz), short pulse (∼100 ns), low voltage (40-80 kV) discharges and then mineralizes the less chlorinated products with aerobic bacteria. A 6.1 mM aqueous dichlorophenol sample was cycled through the PED reactor (60 kV of applied pulsed voltage and 300 Hz) 6 times, resulting in the release of 55% of the initial dichlorophenol chloride ions (1 mM Cl − removed each cycle). The respective average specific efficiency is 0.4-0.6 keV/(Cl − molecule). Pseudomonas mendocina KR1, which grows in minimal medium supplemented with phenol but not with dichlorophenol, increased in cell density in all cultures supplemented with the PED-treated DCP samples and yielded a maximum of twofold additional Cl − released compared to the PED-related alone. The number of PED-treatment cycles, voltage, and frequency were also varied, showing that both cell densities and overall dichlorophenol dechlorination were highly dependent upon the number of PED-treatment cycles, rather than the tested voltages and frequencies. Using this two-stage treatment system, PED released 31% of the initial chloride ions from dichlorophenol (after three cycles at 40-45 kV and 1.2 kHz) while P. mendocina KR1 in the second stage increased dechlorination to 90%. These results were corroborated by the 35% additional chloride release found with activated sludge cultures. Perchloroethylene (0.6 mM) was similarly treated in a first-stage PED reactor (80% chloride removal after four cycles) followed by biodegradation of the dechlorinated products with a recombinant toluene o-monooxygenase-expressing Pseudomonas fluorescens strain. Gas chromatographic analysis showed that the PED reactor created less-chlorinated byproducts (i.e., trichloroethylene) that were removed (74%) upon exposure to the recombinant bacterium.

Electron-driven chemistry of halogenated compounds in condensed phases: Effects of solvent matrices on reaction dynamics and kinetics

“…Studies of EDPs for halogenated compounds have also been motivated by their relevance as electron sinks in situations where it is necessary to extinguish flames, plasmas or arcs. Similarly, the electron-stimulated reactions of organohalides in plasma discharges have been investigated as a remediation technology [26].…”

Degradation of 4-Chlorophenol using a Gas–Liquid Gliding Arc Discharge Plasma Reactor

“…It is found that the use of the discharges in water-gas medium have attracted much attention in recent years [1,5,7,8]. This is caused by the fact that the electrical discharges in two-phase medium not just combine the advantages of gas-phase discharge (i.e., for ozone O 3 and oxygen radical O formation, UV-radiation generation) and liquid-phase discharge (i.e., for hydroxyl radical • OH and hydrogen peroxide H 2 O 2 formation), but also have more advantages: increase of the gas-liquid boundary surface area exposed to hydrated electrons e aq and free radicals; enhancement of the electric field at the droplet surface; concentration of the organics near the droplet surface.…”

“…In recent years, the removal of toxic organic compounds such as phenol, chlorophenol, and others from waste water by high voltage electrical discharges including of spark discharge, corona discharge, and glow discharge represents a very important issue in the environmental technology [1][2][3][4][5][6][7][8]. It is found that the use of the discharges in water-gas medium have attracted much attention in recent years [1,5,7,8].…”

Enhanced degradation of p-chlorophenol in a novel pulsed high voltage discharge reactor

“…In an atomizer reactor used for removal dichlorophenol, the chamber consisted of a hollow, Teflon-coated Lucite cylinder with a set of axially oriented intermeshed electrodes placed in the center [15]. A 6.1 mmol aqueous dichlorophenol sample was cycled through the reactor six times, resulting in the release of 55% of the initial dichlorophenol chloride ions.…”