Elimination of alkanes from off‐gases using biotrickling filters containing two liquid phases

Biological techniques are highly cost‐effective for the treatment of off‐gases containing low concentrations of pollutants (< 5 g/m 3 ). They may also be attractive for the elimination of higher concentrations of explosive hydrocarbons (when compared to incineration). Conventional techniques such as biofilters have low elimination capacities for hydrophobic compounds caused by a poor mass transfer from the gas to the aqueous phase. To overcome solubility problems, a novel biotrickling filter was developed and is characterized by the use of an organic solvent. In such a biotrickling filter, a mixture of an organic solvent and water is continuously trickled over a packed bed, while the polluted gas passes counter‐current to the liquid. The microorganisms exist on the packing material and in the circulating liquid. The alkanes are absorbed in the oil phase of the liquid, transfer red to the microorganisms and biodegraded. Laboratory‐scale experiments at 201 scale with hexane as a model pollutant and silicon oil as a solvent revealed that a 90% elimination efficiency can be reached at a volumetric loading rate of 100g hexane per m 3 filterbed per hour. The influent gas contained 10 g hexane per m 3 and had a temperature of 29°C. The method described in this paper can be a cost‐effective way to treat gases containing hexane, other alkanes or other strongly hydrophobic compounds. Biological co‐oxidation of other biodegradable pollutants from the gas is to be expected.