Bioremediation and Detoxification of Synthetic Wastewater Containing Triarylmethane Dyes by Aeromonas hydrophila Isolated from Industrial Effluent

Abstract

Economical and bio-friendly approaches are needed to remediate dye-contaminated wastewater from various industries. In this study, a novel bacterial strain capable of decolorizing triarylmethane dyes was isolated from a textile wastewater treatment plant in Greece. The bacterial isolate was identified as Aeromonas hydrophila and was shown to decolorize three triarylmethane dyes tested within 24 h with color removal in the range of 72% to 96%. Decolorization efficiency of the bacterium was a function of operational parameters (aeration, dye concentration, temperature, and pH) and the optimal operational conditions obtained for decolorization of the dyes were: pH 7-8, 35°C and culture agitation. Effective color removal within 24 h was obtained at a maximum dye concentration of 50 mg/L. Dye decolorization was monitored using a scanning UV/visible spectrophotometer which indicated that decolorization was due to the degradation of dyes into non-colored intermediates. Phytotoxicity studies carried out using Triticum aestivum, Hordeum vulgare, and Lens esculenta revealed the triarylmethane dyes exerted toxic effects on plant growth parameters monitored. However, significant reduction in toxicity was obtained with the decolorized dye metabolites thus, indicating the detoxification of the dyes following degradation by Aeromonas hydrophila.

Figure 1

Decolorization of synthetic dye wastewater containing triarylmethane dyes under agitated and static conditions by Aeromonas hydrophila (pH 7; 30°C; 24 h). Values are means of triplicate determinations

Figure 2

Decolorization of synthetic dye wastewater at different initial concentrations of triarylmethane dyes by Aeromonas hydrophila (pH 7; 30°C; 24 h). Values are means of triplicate determinations. Error bars represent standard deviations.

Figure 3

Decolorization of synthetic dye wastewater containing triarylmethane dyes at different incubation temperatures by Aeromonas hydrophila (agitated culture; pH 7; 24 h). Values are means of triplicate determinations. Error bars represent standard deviations.

Figure 4

Decolorization of synthetic dye wastewater containing triarylmethane dyes at different initial pH by Aeromonas hydrophila (agitated culture; 35°C; 24 h). Values are means of triplicate determinations. Error bars represent standard deviations.

Figure 5

UV/visible spectra of triarylmethane dyes before and after degradation by Aeromonas hydrophila in synthetic wastewater medium (a) Basic violet 14, (b) Basic violet 3, and (c) Acid blue 90.

Figure 6

Time courses of growth and decolorization of triarylmethane dyes by Aeromonas hydrophila cultured in synthetic wastewater medium (50 mg/L initial dye concentration; pH 7; 35°C) under agitated condition. (a) Basic violet 14 (b) Basic violet 3 (c) Acid blue 90. (◊)—Control (uninoculated medium with dye); (■)—inoculated medium with dye; (▲)—Log cell number in culture. Data represent means (±SD) of triplicate experiments.