The production and accumulation of propionic acid affect significantly anaerobic wastewater treatment system, but the reasons are not approached until now. Based on the results of continuous-flow tests and the analysis of biochemistry and ecology, two mechanisms of producing propionic acid have been put forward. It is demonstrated that the reasons of propionic acid production and accumulation are not caused by higher hydrogen partial pressure. The combination of specific pH value and ORP is the ecological factor affecting propionic acid production, and the equilibrium regulation of NADH/NAD+ ratio in cells is the physiological factor. Meanwhile, it is put forward that using the two-phase anaerobic treatment process and the ethanol type fermentation in anaerobic reactor to avoid propionic acid accumulation are efficient methods.

To improve the hydrogen evolution rate in continuous hydrogen production of a novel fermen-tative hydrogen-producing bacteria st rain B49 (AF481148 in EMBL), 4% immobilized cells by polyvinyl alcohol-boric acid method, with the addition of a small amount of calcium alginate in a column reactor obtain hydrogen yield of 2.31mol H2/mol glucose and hydrogen evolution rate of 1435.4ml/L culture•h respectively at medium retention time of 2.0h with a medium containing 10g glucose/L. Moreover, as the cell density in gel beads is increased to 8%, hydrogen yield and hydrogen evolution rate for 10g glucose/L are 2.34mol H2/mol glucose and 2912.4ml/L culture•h respectively at medium retention time of 1.0h, and for molasses wastewater COD of 7505.9mg/ L hydrogen production potential of 205.6ml/g COD and hydrogen evolution rate of 2057.7ml/L culture•h at hydraulic retention time of 0.75h are observed. In the continuous culture pH value keeps around 3.9 by self-regulating.