Nitrate reduction with Halomonas campisalis: Kinetics of dentrification atpH 9 AND 12.5% NaCl

Regeneration of ion exchange resins with NaCl produces brine containing hig h concentrations of nitrate that can be difficult to remove using standard biological, physical, or chemical technologies. In this study, Halomonas ca mpisalis (ATCC #700597) (Mormile et cit., 1949) was shown to completely red uce nitrate at 125g/L NaCl and pH 9. This organism was also used in experim ents to determine nitrate-reduction rates and biomass yields. Kinetic param eters were measured separately with glycerol, lactate, acetate, ethanol, an d methanol. The specific nitrate-reduction rate coefficient was highest in cultures amended with acetate, while lactate and glycerol (a natural osmoti cum in hypersaline environments) had lower reduction rates. No evidence of nitrate reduction was observed when ethanol or methanol was provided as an electron donor. Kinetic modeling provided values for nitrate and nitrite-re duction rate coefficients and for biomass yields. Measured rates and yields were similar to reported parameters obtained from non-halophilic nitrate-r educing cultures under low salt concentrations. Therefore, for highly salin e solutions, the use of halophiles to selectively remove nitrate from these brines may represent a viable treatment option. (C) 2001 Elsevier Science Ltd. All rights reserved.