Influence of support surface properties on activity of bacteria immobilised on activated carbons for water denitrification

Denitrification of water under anaerobic conditions was carried out by Escherichia coli supported or immobilised on different activated carbons and silica. Results were compared with those obtained when bacteria was used alone or mixed with activated carbons. Denitrification took place in two steps: reduction of nitrate to nitrite, and its subsequent reduction to dinitrogen. The process required an external carbon source that in this case was ethanol. Results obtained in the denitrification process were related to characteristics of activated carbon that favoured bacteria adsorption and to the final pH(PZC) of the activated carbon-bacteria complex. In addition, a large macropore volume also allowed the bacteria to grow during the process. The presence of Cd(II) and Cr(VI) ions negatively affected the denitrification process. However, their influence on the removal of nitrite ions was smaller if the bacteria were supported on activated carbon. (C) 2003 Elsevier Science Ltd. All rights reserved.