Microbial decolorisation of chromium‐azomethine dye under aerobic conditions

Abstract

Removal of an chromium‐containing azomethine dye from waste water using an aerobically grown mixed bacterial culture was studied. Viable cell counts in the dye‐amended medium were determined by serial dilution and expressed as a number of colony forming units (CFU) per unit volume. The extent of decolorisation was found to depend on initial dye concentration, and ranged between 27 and 50%. At low dye concentration initial biosorption was insignificant, and about 50% of dye was subsequently removed by bacterial degradative activity. At high dye concentration initial biosorption was 20% following by almost unchanged CFU level and the presence of only one bacterial type, a gram‐positive bacterium. Consequently at the end of the test only 27% decolorisation was obtained. Concentration of chromium in the solution followed a similar pattern. A higher Cr(III) concentration at the end of the treatment was attributed to chromium release by partial biodegradation of the dye, followed by partial adsorption by bacterial cells and subsequent release by bacterial cell decay.