Abstract
The textile industry consumes water and it produces huge amounts of contaminated water by dyes and some heavy metals that were used to fix textile dyes. The potential ability of the free and immobilized green alga Scenedesmus obliquus (S. obliquus) to degrade azo dyes (Methyl red 20 ppm and Congo red 20 ppm) contaminated with Cu2+ (0.01, 0.1, 0.5 and 1 mg L-1) was studied. The degradation product after decolorization was identified and confirmed by spectroscopic analysis and Fourier transformed infrared spectroscopy analysis, determination of total phenol content and antioxidant content by DPPH. The decolorization ratio of Methyl red and Congo red by S. obliquus was 48.60% and 41.15%, respectively, while when media supplemented with Cu2+ (0.5 mg L-1) were 46.38% and 40.43% after 10 days incubation. The decolorization of both dyes by the alga beads and alginate beads were 55.45% and 26.27% with Methyl red, 50.7% and 21.64% with Methyl red added to Cu2+, 62.05% and 31.2% with Congo red 57.72% and 18.52% Congo red with Cu2+, respectively after 10 d of incubation. Influence of heavy metals as co-contamination decreased the biodegradation of dyes not inhibitor for decolorization by S. obliquus suspension and immobilized. The alga beads are capable of adsorption of Cu2+ and dyes degradations more than the alga in suspension. In general, such a metallic compound appeared to decrease the biodegradation of azo dyes, and with increasing, the concentration of heavy metal there was a decrease in biodegradation efficiency.