Innovative utilization of coal bottom ash for bioremediation of toxic organic pollutants Rivka Cahan a, * , Matanya Stein a, b , Yaakov Anker c , Yakov Langzam b , Yeshayahu Nitzan b a Department of Chemical Engineering, Ariel University, Ariel 40700, Israel b The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel c Samaria and the Jordan Rift Regional R&D Center, Ariel University, Ariel 40700, Israel article info Article history: Received 2 May 2013 Received in revised form 9 August 2013 Accepted 15 August 2013 Available online Keywords: Coal bottom ash Biofilm Cupriavidus basilensis Phenol bioremediation abstract Cupriavidus basilensis cells were grown on coal bottom ash, tuff and gravel in a medium containing phenol. Confocal scanning laser microscope analysis demonstrated a live biofilm on the coal bottom ash, but not on the tuff or gravel. Measurement of the dehydrogenase activity in the biofilm showed an absorbance of 0.697  0.04 at 540 nm when the biofilm was grown on coal bottom ash, and only about 0.002 on tuff and gravel. Planktonic bacterial cells and biofilm which were grown on coal bottom ash degraded 400 mg l 1 phenol within 47  2.5 h and 28  1.7 h, respectively. Optimal phenol degradation occurred between pH 6 and pH 8. Degradation by the biofilm was slower at lower or higher pH values, whereas no degradation was observed by the planktonic bacterial cells at these pH values. The optimum temperature for biodegradation was observed at 28  C. At 37  C and 15  C degradation by the biofilm was slower, whereas no degradation was observed by the biofilm. Repeated biodegradation of the biofilm was carried out for 200 h. The biofilm on the coal bottom ash exhibited a developed network of appendages connecting the bacterial cells to each other. To the best of our knowledge, this study is the first to evaluate coal bottom ash for biodegradation of toxic organic pollutants. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Utilization of coal bottom ash as a porous medium for wastewater treatment has been known since the last century (Wagner et al., 1984; EPA, 1993; Gupta et al., 2012). Bottom ash accounts for 5e15% of the incombustible byproduct collected from the bottom of furnaces in coal fire power plants. It is dark gray, coarse, porous, with sizes ranging from fine sand to fine gravel. Interest in the utilization of bottom ash as a potential adsorbent for removal of pollutants, such as metals (Gorme et al., 2010; Zhang et al., 2011), dyes (Gupta et al. 2004, 2005, 2006, 2009; Mittal et al. 2005, 2008, 2009, 2010) and organic pollut- ants from papermaking (Sun et al., 2008), has been growing in recent years. Bottom ash may, with some restrictions, be regarded as “nontoxic” (EPA, 2003). Its particle size span, inherent large surface area and high porosity make it a good choice for use as a low-cost adsorbent (Gupta et al., 2005) and as a substratum for biofilm growth in order to enhance wastewater bioremediation (Aouad et al., 2006). Evaluation of biofilm growth potential has been performed for carriers with different mineralogical compositions. It was found that while the presence of calcium and alumina suppresses biofilm development, no significant differences were observed between strata composed of various silica combinations. However, the presence of active carbon improved biofilm immobilization (Viggiani et al., 2006; Hrenovic et al., 2009). Phenols are among the major industrial pollutants, due to their frequent presence in the waste effluents of many industrial pro- cesses, such as the production of pesticides, textiles, explosives, plastics, dyes, fertilizers and olive oil extraction. Phenol and its derivatives are toxic to aquatic flora and fauna even at low con- centrations (Agarry et al., 2008a). Exposure to phenol and its de- rivatives may lead to lethal mutations (Semibiring and Winter, 1991) and respiratory disorders. Long-term phenol inhalation may even lead to cancer (Calabrese and Kenyon, 1991). Treatment of phenol effluents is therefore very important. The physico-chemical technologies for phenol decontamination are costly and were found to have a tendency to form secondary toxic intermediates * Corresponding author. Tel.: þ972 3 9066606; fax: þ972 3 9066323. E-mail address: rivkac@ariel.ac.il (R. Cahan). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ibiod.2013.08.010 International Biodeterioration & Biodegradation 85 (2013) 421e428