Impact of metal ions and EDTA on photofermentative hydrogen production by Rhodobacter sphaeroides using a mixture of pre-treated brewery and restaurant effluents

The influence of different concentrations of iron, Fe (30-110 mu M), molybdenum, Mo (8-20 mu M), and ethylenediaminetetraacetic acid, EDTA (0.1-0.5 g L-1) on the photofermentative hydrogen production and bacterial growth by Rhodobacter sphaeroides 158 DSM was investigated and discussed. A blend of pre-treated brewery (30%) and restaurant (70%) effluents was used successfully as sole medium (without using the standard medium) for the photofermentative hydrogen production, producing a cumulative biohydrogen of 83 mL. The results show that sole-additions of Fe at 70 mu M, Mo at 14 mu M, and co-addition of Fe:Mo at 70 mu M:8 mu M to the mixture of pretreated brewery and restaurant effluents, could enhance the cumulative biohydrogen production to 140 mL (69% increased), 105 mL (27% increased), and 160 mL (93% increased), respectively. The results also revealed that the addition of EDTA should be optimized to avoid the chelation of the added metal ions (Fe, Mo). The biohydrogen production was further enhanced to 192 mL, which represent 131% increase compared to control, when the optimized EDTA of 0.2 g L-1 was added the blended effluents at Fe:Mo concentrations of 70 mu M:8 mu M. Furthermore, the study shows that the addition of Fe, Mo and EDTA to the blended effluent enhances the biomass growth as well. Utilizing the wastewater for biohydrogen production as a sole medium could open new era for renewable energy production.