The release of dyes through contaminated water into the ecosystem from various industries like textile, leather, cosmetic, paper, pharmaceutical and food industries is not only a source of aesthetic pollution but also can cause human health disorders and adversely affects the aquatic life causing severe environmental problems worldwide. In view of increasing concern from perspective of environmental safety and health, physico-chemical and biological techniques are to be constantly explored for decolourization and degradation of dyes.
Remazol red RB dye was selected as model azo dye for the study. It is known to be toxicity, mutagenic and carcinogenic in nature because of the presence of the aromatic amine group (Zollinger, 2003; Jalandoni-Buan…show more content… The percentage of decolourization decreased with an increase in initial concentration of dye. This can be attributed to the fact that at lower dye concentration, the ratio of bio sorbent sites to the dye concentration was higher and whereas at higher dye concentration the bio sorbent sites were completely saturated (Özer et al., 2005; Kaushik and Malik, 2010). Similar studies have been reported by (Alhassani et al., 2007; Wang et al., 2009a,b).Reduced decolourization efficiency might be due to the toxicity of dyes (Kapdan et al., 2000; Verma and Madamwar, 2002). Moosvi et al., (2005) with the dye reactive violet 5 at concentration of 50 to 400 ppm observed increase in decolourization with increase in initial dye concentration up to 200 ppm (3.55 mg/l/h) by bacterial consortium RVM 11.1 beyond which there was reduction in decolourization rates. Junarrkar et al., (2006) also showed increase in decolourization with increase in initial dye concentration up to 200 ppm (2.29 mg/l/h) with dye Direct red 81 (50- 400 ppm) using bacterial consortium NBNJ6 however further increase in dye concentration resulted in reduction in decolourization rates. Bhatt Nikhil et al., (2012) they found that the consortium SpNb1 exhibited optimum decolourizing activity at pH 7.5 with maximum dye decolourization and 29.98 mgL-1 h-1 dye removal rates within 9.30 hours at 300 ppm dye concentration. When the dye concentration was high, the isolates showed less capability. Reduction in the decolourization rates might be attributed to the toxicity of dye to bacterial cells through the inhibition of metabolic activity (Sumathi and Manju, 2000), saturation of the bacterial cells with dye products (Sponza and Isik, 2002), inactivation of transport system of the dye or the blockage of active