Optimization of conditions for hydrogen production from complex dairy wastewater by anaerobic sludge using desirability function approach Abhijit Gadhe, Shriram S. Sonawane*, Mahesh N. Varma Department of Chemical Engineering, Visvesvaraya National Institute of Technology (VNIT), South Ambazari Road, Nagpur (M.S.) 440010, India article info Article history: Received 31 January 2013 Received in revised form 8 March 2013 Accepted 14 March 2013 Available online 22 April 2013 Keywords: Optimization Dairy wastewater Biohydrogen production Response surface methodology abstract Present study deals with the multiple-response optimization for biohydrogen production using anaerobic sludge and outstanding approach to overcome the drawbacks of conven- tional response surface methodology (RSM). Dairy wastewater was used as source in batch fermentation was followed for this study. Response surface methodology (RSM), based on a three level, four variable BoxeBehnken design, was employed to obtain the best possible combination of substrate concentration, pH, COD/N ratio and COD/P ratio for maximum H 2 yield (HY) and specific hydrogen production rate (SHPR). Experimental data were evaluated by applying RSM integrating a desirability function approach. The optimum H 2 yield and SHPR conditions were: substrate concentration 15.3 g COD/L, pH 5.5, COD/N ratio 100.5 and COD/P ratio 120 with maximum overall desirability D of 0.94. The confirmation experiment under these optimal condition showed a HY and SHPR of 13.54 mmol H 2 /g COD and 29.91 mmol H 2 /g-VSS.d, respectively. This was only 0.22% and 0.20%, respectively, different from the predicted values, suggesting that the desirability function approach with RSM was a useful technique to get the maximum H 2 yield and SHPR simultaneously. Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, the global energy supply depends on limited resources of fossil fuels, whose combustion contributes to air pollution and the greenhouse effect. Hydrogen is considered as a clean and renewable energy carrier of the future mainly due to its non-polluting nature and energy efficiency [1]. Currently, commercial hydrogen is produced mainly through the energy and environmentally intensive process of fossil fuels reforming, results in massive emis- sion of greenhouse gases [2]. These processes deplete fossil fuels and consume high energy to produce hydrogen [3]. As a result of high energy consumption, the biological hydrogen process is exploited to resolve this limitation. Hydrogen production from biological processes can be divided into two types i.e. photo-fermentation by Cyanobac- teria, algae, photosynthetic and chemosynthetic-fermentative bacteria and dark fermentation by anaerobic bacteria [4]. Hydrogen production from the dark fermentation process by microorganism is more advantageous than photo-fermentation due to high rate of H 2 production and potential to utilize various wastewaters as a substrate [5]. To date, large number of studies has been reported on bioH 2 production from different organic wastes and * Corresponding author. Tel.: þ91 7122801562. E-mail address: shriramsonawane@gmail.com (S.S. Sonawane). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 38 (2013) 6607 e6617 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.2013.03.078