Influence of Added Nutrients and Substrate Concentration in Biohydrogen Production from Winery Wastewaters Coupled to...

Winery wastewaters are acidic effluents with high content of organic matter and nutrients. Different initial values of chemical oxygen demand (COD), ranging from 4 to 50 g L^-1, were tested in batch assays to evaluate the fermentative hydrogen production followed by a methane production step. The influence of adding a typical nutrient solution for hydrogen production was investigated. Nutrients include N-NH₄, Mg, Fe, Co, Mn, I, Ni, and Zn. The best hydrogen production potential was obtained at a COD of 50 g L^-1 without nutrient addition. This condition produced 528 mL H₂ L^-1. At a COD ≥ 35 g L^-1, tests with only WW had a hydrogen potential 1.6 to 1.9 times higher than did tests where nutrients were added. The use of added nutrients reduced the hydrogen production by producing additional reduced acids, such as propionate and valerate. In a second stage, biomethane potential was evaluated using the effluent of a selected condition from hydrogen production tests. The methane production reached values of 207 ± 2.2 mL CH₄ g^-1 COD at 10 g COD L^-1. The COD affected the specific methane production. The results of this study demonstrated the potential of winery effluents as a substrate for sequential hydrogen and methane production to increase the energy recovery from this effluent, with a maximum energetic yield and productivity of 7.15 kJ gCOD^-1 and 11.51 kJ d^-1.