Optimal operational conditions for biohydrogen production from sugar refinery wastewater in an ASBR S.G. Won, S.A. Baldwin, A.K. Lau*, M. Rezadehbashi Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC V6T 1Z3, Canada article info Article history: Received 1 June 2013 Received in revised form 6 August 2013 Accepted 15 August 2013 Available online 14 September 2013 Keywords: Anaerobic sequencing batch reactor Sugar refinery wastewater Hydrogen production Metabolites Taxonomic analysis Clostridium abstract The performance of biohydrogen production in an anaerobic sequencing batch reactor (ASBR) was evaluated with respect to variations in the key operational parameters e pH, hydraulic retention time HRT, and organic loading rate OLR using sugar refinery waste- water as substrate. Analysis of variance (ANOVA) indicated HRT had less significant in- fluence on hydrogen content and yield in comparison to pH and OLR, whereas OLR has much impact on hydrogen production rate. Taxonomic analysis results showed that diverse bacterial species contributed to hydrogen production and the dominant species in the bioreactor were governed by all operational parameters. Even without pretreatment of the seed sludge, a high proportion of Clostridium spp. over the other bacterial species was observed at pH 5.5, and this is compatible with the high hydrogen productivity. Conse- quently, pH 5.5, HRT 10 h, and OLR 15 kg/m 3 d were delineated as the optimal operational conditions for an ASBR fed with sugar refinery wastewater. Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Hydrogen has been deemed the future energy carrier, due to its high energy content and non-polluting nature upon combus- tion to release water vapour. At present, supply of hydrogen is achieved through processes such as steam reforming of methane (a non-renewable fossil fuel source), partial oxidation of hydrogen-rich feedstock, and electrolysis of water. Hydrogen production using biological methods and in partic- ular, from the recycling of organic waste and wastewater, has been regarded as a potentially greener process over conven- tional processes since it does not require high temperature and pressure and hence less energy intensive [1]. Anaerobic fermentation under dark conditions or dark fermentation has proven to be more feasible than photo-fermentation (via photosynthetic bacteria) for practical applications, including integration with fuel cell technologies, because of its much higher hydrogen synthesis rate and efficiency, no requirement of additional light energy, and lower operating cost [2,3]. Experimental studies of hydrogen production using anaerobic fermentation have largely been conducted using continuous stirred tank reactors (CSTRs); the operational conditions are very dependent on the type of substrates and the concentration of carbon sources. Besides, relatively high OLR and short HRT have been applied, and the loss of micro- organisms from the reactor is of concern. While a biofilm reactor using attached microbial growth could avoid this loss of microorganisms [4], an ASBR (define this) also has the * Corresponding author. Tel.: þ1 604 822 3476; fax: þ1 604 822 6003. E-mail addresses: aklau@chbe.ubc.ca, aklau@interchange.ubc.ca (A.K. Lau). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 38 (2013) 13895 e13906 0360-3199/$ e see front matter Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijhydene.2013.08.071