Biodegradation of a Ternary Mixture of Hydrophobic and Hydrophilic VOCs in Trickle Bed Air Biofilters Abderrahman Zehraoui & David Wendell & George A. Sorial Received: 10 March 2014 /Accepted: 9 July 2014 /Published online: 24 July 2014 # Springer International Publishing Switzerland 2014 Abstract The main objective of this study was to evaluate the degradation of a ternary mixture of n-hexane, benzene, and methanol fed to two Trickle Bed Air Biofilters (TBABs) designated as “A” and “B”. Both TBABs were loaded with pelletized diatomaceous earth support media and run at an empty bed residence time (EBRT) of 120 s. TBABs “A” and “B” were operated at pH 4 and fed with n-hexane:benzene:methanol (C H :C B :C M ) concentrations ratios of 1:3:10 and 1:3:6.6, respectively under different loading rates. The influent total loading rates varied from 39.2 to 117.7 g/m 3 h and from 32 to 96.4 g/m 3 h for TBABs “A” and “B”, respectively. In both TBABs, methanol and benzene were the most eliminated volatile organic com- pounds (VOCs), while the removal of n-hexane was con- trolled by the VOCs ratios. Higher removal efficiencies were obtained for the VOCs ratio of 1:3:6.6 corresponding to a total VOCs load of 96.4 g/m 3 h. The addition of VOCs mixture to the TBABs resulted in change of the fungi community within the TBABs as compared to the fungi community when the TBABs were previously receiving only n-hexane as a sole substrate. Keywords Benzene . Biofilters . Biofiltration . Fungi . n-hexane . Methanol . Recalcitrant compounds . Trickle bed air biofilters (TBAB) 1 Introduction As the release of volatile organic compounds (VOCs) into the atmosphere contributes significantly to air pol- lution problem, their emissions from industrial facilities are coming under increased assessment. In fact, with the passage of the 1990 Amendments to the Clean Air Act, these facilities have significantly been affected by the application of rigorous regulations, standards, guide- lines, and codes for VOCs emissions. As a consequence, according to the National Emissions Inventory (NEI) data, national total estimated VOC emissions from an- thropogenic sources (excluding wildfires and prescribed burns) were reduced by 35 % from 23 to 15 Million tons (between 1990 and 2005) (US EPA 2011). However, despite great progress in air quality enhancement, ap- proximately 124 million people nationwide lived in counties with pollution levels above the primary Nation- al Ambient Air Quality Standards (NAAQS) in 2010 (US.EPA 2011). The reduction of VOCs emission, empowered by the treatment of these VOCs, triggered the development of techniques that enhance air quality. Biofiltration was for decades a very economical and environmental friendly technique for combating these VOCs. More interestingly, trickle bed air biofilters (TBABs) were very efficient in treating off-gases emis- sion of hydrophobic, hydrophilic, or mixture of VOCs from a broad spectrum of industrial applications (Balasubramanian et al. 2012; Sempere et al. 2010). Furthermore, in today’ s environment of ever-increasing energy cost and national consciousness of natural re- sources, TBABs provide high efficiency and controllable Water Air Soil Pollut (2014) 225:2075 DOI 10.1007/s11270-014-2075-x A. Zehraoui : D. Wendell : G. A. Sorial (*) Department of Biomedical, Chemical, and Environmental Engineering, College of Engineering and Applied Science, University of Cincinnati, 2901 Woodside Drive, Cincinnati, OH 45221-0012, USA e-mail: George.Sorial@uc.edu