Gliding arc discharge-assisted biodegradation of crystal violet in solution with Aeromonas hydrophila strain

Abstract

The gliding arc discharge, which is a source of nonthermal plasma, was used to enhance the biodegradation of crystal violet (CV), a triphenylmethane nonbiodegradable organic dye. The determination of the biodegradability index, i.e., biochemical oxygen demand (BOD 5 )/chemical oxygen demand (COD) ratio, and the total organic carbon measurement were used to assess the biodegradability. For the biological treatment alone, a bacterial strain of Aeromonas hydrophila (8 9 10 8 -CFU mL -1 ) bleached 42 % of CV solution (50 mg L -1 ) after 12-h incubation. The bleaching rate was enhanced by increasing the initial bacterial concentration; however, a drop in the bleaching rate was noted when CV concentration was increased. For the plasma process alone, a 15-min treatment resulted in a color removal of 49.7 %, at a mineralization rate of 12.2 %, thereby increasing the BOD 5 /COD ratio from 0.11 to 0.23. There was an increase in the bleaching rate in temporal post-discharge conditions (i.e., self-continuity of reaction after the discharge was switched off): For 2 h of temporal post-discharge reaction, the color removal of the 15-min plasma-pre-treated CV increased to 55 %. The disappearance of color during each treatment method followed the first-order kinetics. With regard to the combined plasma/biological treatment process, the 15-min plasma-pre-treated sample was bleached at 92 % by A. hydrophila after 2-h incubation and completely bleached for 6 h. Therefore, there is a positive synergism of bacterial and plasma treatments. This combined treatment is useful in reducing the energy involved in complete mineralization of wastewater containing nonbiodegradable dyes.

Biodegradation kinetic studies and optimization for the elimination of azoic and triphenylmethane dyes using an integrated process combining biological treatment and gliding arc plasma

“…The membrane filtration technique on Ampicillin‐Dextrin Agar medium was used to isolate A. hydrophila strain from well water 20,21 . The techniques of isolation, culture, and suspensions preparation can be found in the preliminary study 16 and in details in the work of Lontsi et al 22 . The strain A. hydrophila was used in the stationary growth phase.…”

“…The membrane filtration technique on Ampicillin-Dextrin Agar medium was used to isolate A. hydrophila strain from well water. 20,21 The techniques of isolation, culture, and suspensions preparation can be found in the preliminary study 16 and in details in the work of Lontsi et al 22 The strain A. hydrophila was used in the stationary growth phase. The bacterial population was assessed by the counting method according to Rodier et al 23 The concentration of each bacterial suspension (CFU mL −1 ) was determined by adjusting the absorbance at 600 nm of the suspension at the desired value.…”

“…It has been largely described elsewhere. 16 It produces an alternative voltage of 9000 V and a current intensity of 100 mA in open conditions and 600 V/160 mA in working conditions. 24 The working gas was humid air (800 L h −1 ) saturated with water.…”

“…These findings complete our previous results on biodegradability enhancement of CV dye. 16 UV/visible spectrophotometric study To identify some of the intermediate species responsible for the biodegradability enhancement of the CV during the GAP treatment, the UV/Visible absorption spectra of the initial CV solution (0 min) and those subjected to plasma gas for 5 and 15 min were presented (Fig. 8).…”

“…14,15 Indeed, we showed this possibility in a preliminary study, by combining the glidarc plasma and the biological treatment for waste remediation. 16 For this purpose, the prior exposure of non-biodegradable crystal violet (CV) dye to plasma caused its efficient subsequent biodegradation by bacteria of Aeromonas hydrophila; however, the quantitative interpretation of results requires a kinetic study. To the best of our knowledge, there is no report focused on the optimization of the biodegradation kinetics of textile dyes pre-treated by glidarc plasma process.…”