| An efficient and stable operational strategy for an anaerobic sequencing batch reactor (ASBR) was studied to overcome inhibitory potential when anaerobically treating synthetic high strength organic wastewaters to produce methane. The ASBR systems, which were operated under batch and fed-batch modes, were conducted at a wide range of volumetric organic loading rate (VOLR) (1.5--24 g COD/L/d) by varying hydraulic retention time (HRT) (1.25, 2.5, and 5 days) at 35°C. The fed-batch mode ASBR, which was operated with a long feed time compared with the usual operation of an ASBR, was the most stabile for treating synthetic organic wastewater, even at the higher VOLR, and provided a higher COD removal efficiency and methane production rate compared to the short feed batch mode in the experimental ranges investigated. The formation of lower volatile fatty acid concentrations for the fed-batch mode confirmed the stability and efficiency of this operational strategy.; The influence of environmental pH and bacterial stress on anaerobic hydrogen production was studied on batch vial cultures and completely mixed batch reactors (CMBRs) to selectively enrich hydrogen-producing species from natural, mixed anaerobic sludge. In the batch vial experiments, the culture at the initial pH 7, using inocula exposed to the bacterial stress of chemical acidification (as perchloric acid), showed the best hydrogen-producing potential of the enrichment procedures studied. The CMBR that was operated with pH controlled at 5.7 had the largest hydrogen production among the observed pH values. The batch vial and CMBR anaerobic fermentation revealed that butyrate formation was correlated to higher hydrogen yield.; The effects of pH and HRT on the acid-phase ASBR were studied with the aim of optimizing the conversion of synthetic organic wastewater (COD of 25,000 mg/L) into bio-hydrogen. A full factorial design using an evolutionary operation was applied, and the experimental results from 20 runs revealed that a maximum hydrogen production rate of 4,460--5,540 mL/L/d was obtained at HRT = 8 h and pH = 5.7. Hydrogen production rate was strongly dependent on HRT, and the effect (P < 0.05) was statistically significant. The hydrogen-producing acid-phase ASBR had a higher hydrogen production rate compared to that produced using continuous-flow stirred tank reactors. |
