초록
<P><B>Highlights</B></P><P>► The effects of initial lactic acid concentration, OLRs, HRTs on hydrogen production at pH 4.5 were evaluated. ► Even though lactate was one of the major VFAs, hydrogen production was feasible via the continuous operation. ► Cumulated butyric acid by high OLR on continuous hydrogen production decreased hydrogen production efficiency. ► HRT should be determined with soluble metabolite concentration, OLR, and avoiding wash-out of the bacteria.</P> <P><B>Abstract</B></P><P>A batch test and continuous operation were performed to identify the effect of lactate on hydrogen production at pH 4.5. When the initial lactic acid concentration was increased from 0 to 8g/L in the batch test, the hydrogen yield also increased from 1.41 to 1.72mol-H<SUB>2</SUB>/mol-glucose. The system exhibited a long lag time and an insignificant hydrogen yield with 16g-lactic acid/L. A continuous stirred tank reactor (CSTR) was operated at different organic loading rates (OLRs: 10, 15, 20 and 40g/L/day) and hydraulic retention times (HRTs: 6, 12 and 24h). At an OLR of 20g-glucose/L/day and 12h of HRT, the hydrogen yield was 1.2mol-H<SUB>2</SUB>/mol-glucose. The yield decreased with a 24h HRT. Even though lactate was one of the major constituents of volatile fatty acids (VFAs), hydrogen production was feasible throughout the operation. <I>Clostridium</I> sp. was the dominant hydrogen-producing bacteria in the system.</P>