Decolorization of triphenylmethane dyes using immobilized cells of bacterial consortium

The use of freely suspended microbial cells for dye removal is limited owing to their inherent disadvantages such as clogging of cells, low mechanical strength of the biomass etc. Immobilized cells offer advantages over dispersed cells such as high cell density, strong endurance of toxicity for being high in numbers, lower operating costs, simple maintenance management and production of smaller residual sludge. In this study immobilized cell mass of a bacterial consortium, isolated from dye contaminated wastewater, was used to decolorize a mixture of triphenylmethane dyes: Malachite Green, Crystal violet and Basic Fuchsin. Among all the matrices studied calcium alginate showed maximum decolorization with immobilized biomass. Therefore, cells immobilized on calcium alginate matrix was considered for studying the removal of triphenylmethane dyes. Effects of various parameters viz. alginate concentration, bead size, bacterial cell numbers, initial dye concentration, time, pH and temperature were investigated in batch system. The optimum conditions for removal of the dyes were found to be pH 8, temperature 37°C, alginate concentration of 2% (w/v), a cell concentration of 1×10 cells/ml. The dye removal capacity of the immobilized cells decreased as the initial dye concentration increased.