초록
The aim of this work was to study an externally-submerged membrane bioreactor for the cyclic extraction of volatile fatty acids (VFAs) during anaerobic fermentation, combining the advantages of submerged and external technologies for enhancing biohydrogen (BioH<SUB>2</SUB>) production from agrowaste. Mixing and transmembrane pressure (TMP) across a hollow fiber membrane placed in a recirculation loop coupled to a stirred tank were investigated, so that the loop did not significantly modify the hydrodynamic properties in the tank. The fouling mechanism, due to cake layer formation, was reversible. A cleaning procedure based on gas scouring and backwashing with the substrate was defined. Low TMP, 10<SUP>4</SUP>Pa, was required to achieve a 3Lh<SUP>-1</SUP>m<SUP>-2</SUP> critical flux. During fermentation, BioH<SUB>2</SUB> production was shown to restart after removing VFAs with the permeate, so as to enhance simultaneously BioH<SUB>2</SUB> production and the recovery of VFAs as platform molecules.