In Situ Bioremediation of Textile Dye Effluent-Contaminated Soils Using Mixed Microbial Culture

In situ bioremediation is proposed as a low cost and environmental friendly technology for clean-up of land discharge sites of textile industries. Owing to the large range of dye molecules in the environment, a treatment system using mixed microbial culture is proposed. The mixed microbial population possesses higher degree of biodegradation due to synergistic metabolic activities of the microbial community. In the present study, mixed microbial cultures were cultured from four different sources. The dyes used in the experiments were Direct Red 28, Direct Blue 53 and Azur Blue. Batch studies for industrial application were also attempted to treat sludge landfills for chemical coagulation units of dye effluent treatment plants. Finally, a downward flow continuous flow soil reactor was set up to study the robustness of the technology over long duration of operation. Rate of recharge of mixed dye during the trials was 2 mg per hour per kg of soil. Colour removal of 85% (measured at 595 nm) was observed in the first day and 90% in the second day. A steady removal rate of 98% was observed from the 13th day of operation. Fate of the dye molecules was studied using scanning electron microscope (SEM) and Fourier transform infraRed (FTIR) analysis to establish colour removal due to biodegradation.