Absorption and biodegradation of toluene: Optimization of its initial concentration and the biodegradable non-aqueous phase liquid volume fraction

• Biodegradation of toluene by activated sludge in an emulsion of water/DEHP was examined.
• The biodegradation of the selected organic solvent (DEHP) was also targeted.
• High absorption capacity of toluene in DEHP (H = 0.99 Pa m3 mole−1).
• Toluene concentration of 106 mg l−1 and a volume ratio of 0.1% were considered.
• Total toluene consumption and 87% DEHP degradation were found.

Di (2-EthylHexyl) Phthalate (DEHP) was selected as a biodegradable organic solvent to be implemented in a two-phase partitioning bioreactor (TPPB) dedicated to remove a model hydrophobic volatile organic compound (VOC), toluene. In a first step, the absorption capacity of toluene in the selected organic solvent was examined according to the partition coefficients H. In a second step, toluene biodegradation in DEHP by non-acclimated activated sludge was carried out for different volume fractions of DEHP in water and five different toluene concentrations (4.3, 43, 106, 212 and 430 mg l−1). Toluene showed high affinity for DEHP with H = 0.99 Pa m3 mole−1. Both toluene and DEHP were completely consumed for 4.3 mg l−1 (initial toluene concentration) and a volume ratio of 0.1% DEHP in water. For an initial toluene concentration of 106 mg l−1 and a volume ratio of 0.1%, total toluene consumption and 87% DEHP degradation yield were obtained after seven days of incubation.