Effect of surfactant and oil additions in the biodegradation of hexane and toluene vapours in batch tests

Abstract

The biological treatment of gaseous emissions of hydrophobic volatile organic compounds (VOCs) results in low rates of elimination partially because of the low solubility of VOCs in water. Recently, the use of two‐phase partition bioreactors (TPPBs) was proposed to increase the bioavailability and consequently the elimination capacities of this kind of VOC. In the present study, TPPBs operating in a batch feed mode were tested for biodegradation of hexane and toluene vapours with a microbial consortium. The results obtained were compared with single‐phase systems (control experiments). The liquid phase used was silicone oil (organic phase) with the surfactant Pluronic F‐68. Experiments were named F1 and F2 for one and two phases, respectively, and F1S and F2S when the surfactant was included. The maximum specific rates (Srates) of hydrocarbon consumption for hexane and toluene were 539 and 773 mghydrocarbon/(gprotein·h), respectively. For both substrates, the systems that showed the highest Srates of hydrocarbon consumption were F2 and F2S. In experiment F1S the surfactant Pluronic F‐68 increased the solubility of hydrocarbons in the liquid phase, but did not increase the Srates. The maximum percentages of mineralization were 51% and 72% for hexane and toluene, respectively. The results showed that simultaneous addition of silicone oil and surfactant favours the mineralization, but not the rate of biodegradation, of toluene and hexane vapours.