Research review paper Recent advances in two-phase partitioning bioreactors for the treatment of volatile organic compounds Raúl Muñoz a, ⁎, Andrew J. Daugulis b , María Hernández a , Guillermo Quijano a a Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina, s/n, 47011, Valladolid, Spain b Department of Chemical Engineering, Queen's University, Kingston, Ontario, Canada abstract article info Available online 31 August 2012 Keywords: Biological gas treatment Bioreactor configuration Mass transfer Microbiology Two-phase partitioning bioreactor Volatile organic compounds Biological processes are considered to be the most cost-effective technology for the off-gas treatment of vol- atile organic compounds (VOC) at low concentrations. Two-phase partitioning bioreactors (TPPBs) emerged in the early 1990s as innovative multiphase systems capable of overcoming some of the key limitations of tra- ditional biological technologies such as the low mass transfer rates of hydrophobic VOCs and microbial inhi- bition at high VOC loading rates. Intensive research carried out in the last 5 years has helped to provide a better understanding of the mass transfer phenomena and VOC uptake mechanisms in TPPBs, which has sig- nificantly improved the VOC biodegradation processes utilizing this technology platform. This work presents an updated state-of-the-art review on the advances of TPPB technology for air pollution control. The most re- cent insights regarding non-aqueous phase (NAP) selection, microbiology, reactor design, mathematical modeling and case studies are critically reviewed and discussed. Finally, the key research issues required to move towards the development of efficient and stable full-scale VOC biodegradation processes in TPPBs are identified. © 2012 Elsevier Inc. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1707 2. Process design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1708 2.1. NAP selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1709 2.2. Microbiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1711 2.3. Reactor configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1712 3. Recent studies on gas treatment in TPPBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1713 3.1. Studies at steady loading conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1713 3.2. Studies at transient loading conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1713 3.3. TPPB performance under more realistic scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1715 3.4. Influence of the operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1715 4. Modeling of TPPBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1716 5. Conclusions and future challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1718 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1718 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1718 1. Introduction Emission inventories have revealed that atmospheric pollutant emissions have continuously increased since the beginning of the 20th century, with volatile organic compounds (VOCs) representing about 7% of these emissions (Delhomenie and Heitz, 2005). Despite this low emission share, VOC emissions represent a major environmen- tal and human health problem since most VOCs can be toxic depending on the concentration and exposure time and they also contribute to substantial damage to natural ecosystems (Delhomenie and Heitz, 2005; Hernandez et al., 2010; Muñoz et al., 2007). In addition, VOCs such as methane are greenhouse gases with high global warming po- tential (Rocha-Rios et al., 2009), while ozone formation is driven by the rapid photochemical oxidation of non-methane VOCs in the pres- ence of nitrogen oxides (West and Fiore, 2005). Therefore, governments Biotechnology Advances 30 (2012) 1707–1720 ⁎ Corresponding author. Tel.: +34 983186424; fax: +34 983423013. E-mail address: mutora@iq.uva.es (R. Muñoz). 0734-9750/$ – see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.biotechadv.2012.08.009 Contents lists available at SciVerse ScienceDirect Biotechnology Advances journal homepage: www.elsevier.com/locate/biotechadv