Bacterial mediated bio-decolourization of wastewater containing mixed reactive dyes using jack-fruit seed as co-substrate: Process optimization

Abstract

Abstract The co-substrate is an important ingredient in the bio-decolourization process to promote the healthy growth and basic activities of bacteria. Most widely used co-substrates in bio-decolourization process are expensive and increase the carbon and nitrogen loading in treated water. The present study aims to investigate the bacterial mediated decolourization of azo (reactive red-21 and reactive orange-16), and anthraquinone (reactive blue-19) dyes using jack-fruit seed powder as co-substrate. The study reveals (mere adsorption of dye by jack-fruit seed is ruled out through controlled experiments) that decolourization of dyes using jack-fruit seed containing medium is a bacterial mediated process, in which bacteria use dye compounds as substrate and jack-fruit-seed as co-substrate. The bacterium participated in the decolourization process in presence of jack-fruit seed is classified as Pseudomonas aeruginosa SVM16 by nucleotide sequencing and phylogenetic analyses method. The effect of process parameters on decolourization performance is investigated through response surface methodology. The result reveals that the bacteria have shown capability to decolourize initial 50 mg/L of individual dye solution of reactive red-21, reactive orange-16, and reactive blue-19 by 97.7 ± 0.3%, 98.9 ± 0.3%, and 92.6 ± 0.4%, respectively. The reduction of American dye manufactures institute index values of mixed-dye solutions (reactive red-21, and reactive orange-16) and (reactive red-21, reactive orange-16, and reactive blue-19) though bio-decolourization is achieved as ∼82.7 ± 0.4% and 76.8 ± 0.4%, respectively. The bacteria have shown high salt tolerance (∼6 g/L NaCl). The jack-fruit seed supplemented decolourization process reveals that treated water has shown lesser residual organic and colour loading compared to treated water obtained from bio-decolourization process using yeast extract or other chemicals as co-substrate. The treated aqueous solutions are analysed through ATR-FTIR, GC-MS, and 1H NMR which confirm the almost complete mineralization of dye molecules through bio-decolourization process and non-toxicity of treated water proves through positive germination test of Vigna radiata seeds.