Abstract
Shewanella xiamenensis G5-03 was observed to decolorize the azo dye Congo red in synthetic wastewater. The influence of some factors on the dye decolorization efficiency was evaluated. The optimal decolorization conditions were temperature 30-35 °C, pH 10.0, incubation time 10 h, and static condition. The kinetic of Congo red decolorization fitted to the Michaelis-Menten model (Vmax = 111.11 mg L-1 h-1 and Km = 448.3 mg L-1). The bacterium was also able to degrade benzidine, a product of azo bond breakage of the Congo red, which contributed to reduce the phytotoxicity. The ability of S. xiamenensis G5-03 for simultaneous decolorization and degradation of Congo red shows its potential application for the biological treatment of wastewaters containing azo dyes.
Highlights
The textile industry produces large volumes of effluents containing residues of dyes, metals, COD, BOD, total solids, and variable pH (Holkar et al, 2014)
Effect of pH and temperature on Congo red (CR) decolorization The pH and temperature play a crucial role in the optimal physiological performance of microorganisms during the decolorization process
The germination indexes (GI) of O. basilicum and E. sativa that were grown in untreated synthetic wastewater were 74.0 and 88.3%, respectively, and after 10 h of decolorization, decreased to 38.1 and 41.9%. These results indicated that the decolorization products, including benzidine formed during the cleavage of azo bonds, are more toxic than the CR
Summary
The textile industry produces large volumes of effluents containing residues of dyes, metals, COD, BOD, total solids, and variable pH (Holkar et al, 2014). Because of that, they are the cause of serious environmental concerns. Many textile dyes and some of their metabolites are toxic, mutagenic, and carcinogenic (Saratale et al, 2011). They must be removed from the effluent before its disposal. Several physicochemical effluent treatment processes, including coagulation, electrocoagulation, adsorption, ozonation, and photon-Fenton oxidation, have been reported for the removal of dyes (Castro et al, 2017)
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