Treatment of azo dye (congo red) solution in fluidized bed bioreactor with simultaneous approach of adsorption coupled with biodegradation: optimization by response surface methodology and toxicity assay

This research work aims to investigate the removal of congo red dye by an integrated approach using immobilized microorganism on fly ash in a fluidized bed bioreactor. This reactor offers the advantage of less retention time, high biomass concentration and no bed clogging. The experiments were also carried out in batch mode of operation. Biodegradation of azo dye was ascertained by Fourier-transform infrared spectroscopy. Experimental parameters of azo dye removal were optimized by response surface methodology using central composite design. At optimized operational parameters, dye removal efficiency was determined to be 98.2%. The dye removal was higher in fluidized bed bioreactor than that obtained in a batch reactor. This along with the results of phytotoxicity analysis using Cicer arietinum (Chick pea) seeds indicated that fluidized bed bioreactor is ecologically favourable application for sufficient detoxification of wastewater using immobilized bacterial species. Graphic abstract:

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