ИСТИНА

The anaerobic decolourization of individual azo dyes (Acid Orange 7 and Methyl Red) and their mixture was investigated under methanogenic conditions with addition of ethanol as an exogenic electron donor. The decolourization process followed the first-order kinetics and the corresponding constants decreased with increasing dye concentrations from 100 to 400 mg/l for each dye. This was caused by a toxic influence of azo dyes on anaerobic microorganisms generating reducing equivalent for azo dye decomposition process. It was found that Acid Orange 7 exerted a greater inhibitory effect on the decolourization of Methyl Red than vice versa. The pH optimum for decolourization was 7.5-8.0 for both the individual dyes and their mixture