Journal of Hazardous Materials 262 (2013) 732–740 Contents lists available at ScienceDirect Journal of Hazardous Materials jou rn al hom epage: www.elsevier.com/locate/jhazmat By-passing acidification limitations during the biofiltration of high formaldehyde loads via the application of ozone pulses Teresa García-Pérez a , Aitor Aizpuru b , Sonia Arriaga a,∗ a División de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica (IPICyT), Camino a la Presa San José 2055, Col. Lomas 4 a Sección, San Luis Potosí, SLP 78216, Mexico b Universidad del Mar, Puerto Ángel, Distrito de San Pedro Pochutla, Oaxaca, México C.P. 70902, Mexico h i g h l i g h t s • Ozone addition permits to treat higher formaldehyde loads than ever reported. • Ozone addition acts as an indirect in situ pH regulator, minimizing the accumulation of acid byproducts. • Mineralization of formaldehyde occurs, which has never been reported. • Low ozone levels have no nega- tive effects on biological degradation activity. • The use of hybrid processes allows overcoming biofiltration limitations. g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 9 July 2013 Received in revised form 11 September 2013 Accepted 23 September 2013 Available online xxx Keywords: Biofiltration Formaldehyde Ozone pulses pH Extracellular polymeric substances a b s t r a c t A formaldehyde airstream was treated in a biofilter for an extended period of time. During the first 133 days, the reactor was operated without ozone, whereas over the following 82 days ozone was inter- mittently implemented. The maximum stable elimination capacity obtained without ozone was around 57 g m -3 h -1 . A greater load could not be treated under these conditions, and no significant formaldehyde removal was maintained for inlet loads greater than 65 g m -3 h -1 ; the activity of microorganisms was then inhibited by the presence of acidic byproducts, and the media acidified (pH < 4). The implementation of ozone pulses allowed a stable elimination capacity to be obtained, even at greater loads (74 g m -3 h -1 ). The effect of ozone on the extra cellular polymeric substances detachment from the biofilm could not be confirmed due to the too low biofilter biomass content. Thus, the results suggest that ozone acted as an in situ pH regulator, preventing acidic byproducts accumulation, and allowing the treatment of high loads of formaldehyde. © 2013 Elsevier B.V. All rights reserved. Abbreviation: W/O3, without ozone. ∗ Corresponding author. Tel.: +52 444 834 2000; fax: +52 444 834 2010. E-mail addresses: sonia@ipicyt.edu.mx, sonia arriaga@yahoo.com.mx (S. Arriaga). 1. Introduction Volatile organic compounds (VOCs) are an important group of compounds that cause serious air pollution concerns [1]. Formaldehyde, one of the most common VOCs, is widely used in many industries as a disinfectant, preservative, and fungicide [2,3], and is recognized as highly toxic [3–5]. In order to reduce 0304-3894/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhazmat.2013.09.053