Batch Nitrifying Cultures in Presence of Mixtures of Benzene, Toluene, and m-Xylene

Abstract

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).

Keywords:

• BIOTRANSFORMATION
• BTX COMPOUNDS
• INHIBITION
• KINETICS
• NITRIFICATION