Optimization of conditions for hydrogen production from complex dairy wastewater by anaerobic sludge using desirability function approach

• The key variables for H2 production were optimized by Box–Behnken Design of RSM.
• Factors included substrate conc., pH, COD/N and COD/P ratio added.
• Optimum conditions were 15.3 g COD/L, 5.5, 100.5, and 120.5, respectively.
• Desirability function was used for concurrent maximization of rate and H2 yield.
• HY of 13.54 mmol H2/g COD and SHPR of 29.91 mmol H2/g-VSS.d were achieved.

Present study deals with the multiple-response optimization for biohydrogen production using anaerobic sludge and outstanding approach to overcome the drawbacks of conventional 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 Box–Behnken design, was employed to obtain the best possible combination of substrate concentration, pH, COD/N ratio and COD/P ratio for maximum H2 yield (HY) and specific hydrogen production rate (SHPR). Experimental data were evaluated by applying RSM integrating a desirability function approach. The optimum H2 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 H2/g COD and 29.91 mmol H2/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 H2 yield and SHPR simultaneously.