Effects of different quinoid redox mediators on the removal of sulphide and nitrate via denitrification

The impact of different quinoid redox mediators oil the Simultaneous conversion of sulphide and nitrate in a denitrifying culture was evaluated. All quinones evaluated, including anthraquinone-2.6-disulphonate (AQDS), 2-hydroxy-1,4-naphthoquinone and 1,2-naphthoquinone-4-sulphonate (NQS) were reduced by sulphide under abiotic conditions. NQS showed the highest reduction rate by sulphide (132 mu mol h(-1)) and promoted the maximum rate of sulphide oxidation (87 mu mol h(-1)) by denitrifying sludge, which represents an increase of 44% compared to the control lacking quinones. The reduced form of AQDS (AH(2)QDS) served as an electron donor for the microbial reduction of nitrite and NO, which represents the first demonstration of hydroquinones supporting the microbial reduction of denitrifying intermediates. The results taken as a whole suggest that some quinones may significantly increase the rate of removal of S and N under denitrifying conditions. (C) 2007 Elsevier Ltd. All rights reserved.