Use of potential bacterial strains to remove Hexavalent Chromium from an aqueous medium and the Periyar River sediments

Abstract

Chromium is one of the most abundant metals in the earth's crust mined as chromites. Industries that widely use compounds containing chromium as Cr(III) in the tanning process generally release effluents with high chromium levels into natural water resources, frequently without appropriate effluent treatment. Though physical and chemical methods of chromium removal are adopted, the processes are expensive, use a lot of energy and generate secondary toxic waste. The removal of chromium by biological resources on the other hand is more environmentally friendly, less expensive, and lacks the release of secondary pollutants. The present study is aimed towards the assessment of the Cr(VI) reduction capability of two bacterial strains, Alcaligenes sp. (S11) and Listeria sp. (S18) used as a consortium. These bacterial strains were isolated from the Periyar river of Kerala, India. Batch mode studies were carried out by live bacterial cells and an integrated study was carried out to test the bacterial strains on chromium-contaminated water and sediments through bioreactor and column study respectively under optimized conditions. The phytotoxicity of the treated water was studied on black gram. In the bioreactor study, the maximum Cr(VI) reduction capacity of bacterial consortium (S11 and S18) was found to be 97%. The successive experiment for the toxicity of treated water on the black gram indicated that there was no toxicity in the growth parameters of the plant.