Long Term Operation of Biological Hydrogen Production in Anaerobic Sequencing Batch Reactor (ASBR)

Long term hydrogen production was investigated in an anaerobic sequencing batch reactor (ASBR) using mixed microflora. Glucose (about 8,250 mg/L) was used as a substrate for the ASBR operation under the condition of pH 5.5 and 37°C with mixing at 150 rpm. The experiment was carried out over a period of 160 days. Hydrogen yield was 0.8 mol H2/mol glucose with F/M ratio 2 at initial operation period. The hydrogen yield reached to maximum 2.6 mol H2/mol glucose at 80th day operation. However decreased hydrogen yield was observed after 80 days operation and eventually no hydrogen yield. Although well-known hydrogen producer Clostridium sp. was detected in the reactor by PCR-DGGE analysis, changed reactor operation was the major reason of the decreased hydrogen production, such as low F/M ratio of 0.5 and high propionic acid concentration 2,130 mg/L. Consequently the long period operation resulted in MLSS accumulation and then low F/M ration stimulating propionic acid formation which consumes hydrogen produced in the reactor.