Removal of Cr (VI) from tannery effluents with mixed cultures of bacteria and fungi isolated from soils contaminated with tropical tannery effluents

Abstract

Pseudomonas aeruginosa, Escherichia coli, Aspergilllus niger and Penicillium chrysogenum isolated from tannery effluent-contaminated soil showed resistance to chromium [Cr (VI)] with minimum inhibitory concentrations (MIC) of 80-120 mg/l in potato dextrose or nutrient agar. This increased to 100-150 mg/l in glucose and yeast extract supplemented mineral salts medium. Significant removal of Cr (VI) occurred in tannery effluents treated with the isolates singly, although reductions were >0.05 mg/l (stipulated limit) in all treatments. Chromium was reduced in glucose, beef and yeast extracts supplemented effluents to non-detectable levels < 0.05 mg/l in all except in E. coli treatment. However, mixed cultures' treatment of non-supplemented effluent reduced Cr (V1) below 0.05 mg/l with the consortium of P. aeruginosa, P. chysogenum and A. niger reaching 99.6-100% removal. Mixed bacterial and fungal culture may be of potential cost effective application in the removal of chromium in tannery wastes.