Batch nitrifying cultures in presence of mixtures of benzene, toluene, and m-xylene.

Benzene, toluene, and m-xylene compounds in individual (5.0 +/- 0.5 mg C l(-1)) and mixed solutions (2.5 +/- 0.2 mg C l(-1) for each one) in nitrifying batch cultures induced a decrease in the specific rates of NH4+ consumption (81 +/- 6%) and NO3- production (39-79%). However, after 24 h, ammonium consumption efficiency and conversion of consumed NH4+ -N into NO3- -N were close to 100% and there was no significant accumulation of nitrite in the medium. After 24 h, no aromatic intermediate was detected in the cultures and 50% of the mixed compounds was converted to acetate. The following order of biotransformation was found: m-xylene > toluene > benzene. Transformation rate of m-xylene was 0.051 +/- 0.005 g C (g protein-N h)(-1) in individual and mixed solutions. When m-xylene was added, benzene was oxidized at a faster rate (0.051 +/- 0.005 g C (g protein-N h)(-1)) whereas toluene at a slower rate (0.012 +/- 0.002 g C (g protein-N h)(-1)).