Biohydrogen production from dairy industry wastewater in an anaerobic fluidized-bed reactor

Abstract

The present study evaluated the influence of organic loading rate in biohydrogen production from dairy wastewater in an anaerobic fluidized-bed reactor inoculated by natural fermentation of the wastewater used during the operational period. The support material for biomass adhesion was shredded tire. The reactor had a working volume of 908.4 cm3. Biohydrogen production was evaluated using three different organic loading rates (OLR) of 28.7 kgCOD m−³d−1, 53.2 kgCOD m−³d−1 e 101,7 kgCOD m−³d−1 corresponding to the Hydraulic Retention Time (HRT) of 8 h (2.7 L d−1), 6 h (3.6 L d−1) and 4 h (5.4 L d−1), respectively. The hydrogen yield decreased with increasing organic loading rate (OLR) from 2.56 ± 0.62 mol H2 mol carbohydrate−1 to 0.95 ± 0.28 mol H2 mol carbohydrate−1 as the OLR increased from 28.65 kgCOD m−³d−1 to 95.76 kgCOD m−³d−1. The hydrogen content in the biogas (volume of H2/ volume of biogas) produced and the highest volumetric production were respectively 35.72 ± 9.43% and 0.80 ± 0.21 LH2 h−1 L−1 obtained when the OLR was 53.25 ± 7.81 kgCOD m−³d−1. The main metabolites produced were acetic acid (67.15%-87.42%) and ethanol (6.01%-13.09%). Increasing the applied OLR also caused an increase in bacterial diversity as evidenced by the highest value of the Shannon-Wiener index (2.811) corresponding to the operational phase of the highest OLR (95.76 ± 29.10 kgCOD m−³d−1).