Anaerobic hydrogen production from sucrose using an acid-enriched sewage sludge microflora

Abstract

A novel and high-rate anaerobic sequencing bath reactor (ASBR) process was used to evaluate the hydrogen productivity of an acid-enriched sewage sludge microflora at a temperature of 35°C. In this ASBR process a 4 h cycle, including feed, reaction, settle, and decant steps, was repeatedly performed in a 5 L reactor. The sucrose substrate concentration was 20 g COD/L; the hydraulic retention time (HRT) was maintained at 12-120 h at the initial period and thereafter at 4-12 h. The reaction/settle period ratio, which is the most important parameter for ASBR operation was 1.7. The experimental results indicated that the hydrogenic activity of the sludge microflora was HRT-dependent and that proper pH control was necessary for a stable operation of the bioreactor. The peak hydrogenic activity value was attained at an HRT of 8 h and an organic loading rate of 80 kg COD/ m3 × day. Each mole of sucrose in the reactor produced 2.8 mol of hydrogen and each gram of biomass produced 39 mmol of hydrogen per day. An overly-short HRT might deteriorate the hydrogen productivity. The concentration ratios of butyric acid to acetic acid, as well as volatile fatty acid and soluble microbial products to alkalinity can be used as monitoring indicators for the hydrogenic bioreactor. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.