The effects of Cr(VI) and Cr(III) s

The effects of Cr(VI) and Cr(III) species on the activated sludge growth rate have been assessed for a batch growth system, for a range of chromium concentration between 0 and 320mgl−1. Cr(VI) was found to stimulate microbial growth for concentrations up to about 25mgl−1, exhibiting maximum growth stimulation at 10mgl−1, whilst the lethal dose was found to be between 80 and 160mgl−1. On the other hand, Cr(III) was also found to stimulate microbial growth for concentrations up to about 15mgl−1, (with a maximum stimulation concentration at 10mgl−1), whilst the lethal dose was found to lie between 160 and 320mgl−1. The results indicate that Cr(VI) is more toxic to biomass at relatively high concentrations (higher than 70mgl−1) whilst it has a more pronounced growth stimulation effect at relatively smaller concentrations (less than 25mgl−1), compared with Cr(III).

© 2005 Elsevier B.V. All rights reserved.