Factors affecting the biological removal of hexavalent chromium using activated sludges Chapter 8 . .

CONTRERAS E.M., FERRO OROZCO A.M., ZARITZKY N.E.

Management of Hazardous Residues Containing Cr(VI)

Nova Science Publishers, Inc. New York

Lugar: New York; Año: 2011; p. 109 - 134

Factors affecting the  biological removal of hexavalent chromium using activated sludges. Contreras E.M., Ferro Orozco A.M., Zaritzky N.E. Chapter 8. En:  Balart M. (Ed.) Management of Hazardous Residues Containing Cr(VI).  Nova Science Publishers, Inc. New York. (2011). pp. 109-134. ISBN:  978-1-61668-267-5 For many years, conventional Cr(VI) removal was achieved by chemical reduction, ion exchange or adsorption. Because of the high costs associated with physical-chemical processes to remove Cr(VI), the search for new technologies has focused attention on the biotransformation of Cr(VI). Several researchers demonstrated that most of bacteria present in activated sludges are capable of reducing Cr(VI) to Cr(III). For this reason, removal of Cr(VI) using activated sludge is a promising technique. This chapter addresses the effect of important factors concerning the bioreduction of Cr(VI) by activated sludge in batch reactors, such as, biomass concentration, the presence, type, and concentration of carbonaceous substrates, the nitrogen source concentration, and Cr(VI) concentration. In addition, a mathematical model that describes the Cr(VI) bioreduction kinetics is also discussed.The reduction of Cr(VI) to Cr(III) in activated sludge batch reactors is a catalytic mediated process associated with the presence of biomass. Although the biomass itself could serve as the electron donor for reducing Cr(VI) to Cr(III), an external electron donor (e.g. carbonaceous substrate) increased the rate and extent of Cr(VI) reduction. High Cr(VI) reduction rates were obtained with fermentable substrates such as cheese whey, lactose, and glucose. On the contrary, with non-fermentable substrates such as citrate and acetate, Cr(VI) removal rates were slower. The low fraction of electrons of the carbonaceous substrate that reduce Cr(VI) to Cr(III) suggests that Cr(VI) reduction in activated sludge batch reactors is mainly via a cometabolic pathway. Editors: María José Balart MurriaSeries:   Waste and Waste Management.     Pub. Date: 2011 - 2nd Quarter,   Pages: 7 x 10, 378 pp.   ISBN: 978-1-61668-267-5