Biohydrogen production under hyper salinity stress by an anaerobic sequencing batch reactor with mixed culture

Abstract

BackgroundThis study investigated the effect of organic loading rate (OLR) and NaCl concentration on biohydrogen production by preheated anaerobic sludge in a lab scale anaerobic sequencing batch reactor (ASBR) fed with glucose during long time operation.MethodsDuring ASBR operation, the OLR was increased in steps from 0.5 to 5g glucose/L.d and NaCl addition started at an OLR of 5g glucose/L.d, to obtain NaCl concentrations in the reactor in the range of 0.5-30g/L.ResultsWith an increasing OLR from 0.5 to 5g glucose/L.d, the biohydrogen yield increased and reached 0.80.4mol H-2/mol glucose at an OLR of 5g glucose/L.d. A NaCl concentration of 0.5g/L resulted in a higher yield of biohydrogen (1.1 +/- 0.2mol H-2/mol glucose). Concentrations above 0.5g/L NaCl led to decreasing biohydrogen yield and the lowest yield (0.3 +/- 0.1mol H-2/mol glucose) was obtained at 30g/L of NaCl. The mass balance errors for C, H, and O in all constructed stoichiometric reactions were below 5.Conclusions The modified Monod model indicated that r (H2)max and Ccrit values were 23.3mL H2/g VSS/h and 119.9g/L, respectively. Additionally, ASBR operation at high concentrations of NaCl shifted the metabolic pathway from acidogenic toward solventogenic.