地球環境に優しい水処理技術としてのメタン発酵法の開発

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The use of methane fermentation as a general process for the treatment of various types of wastewater was evaluated, using an anaerobic fluidized-bed reactor(AFBR). Good performance of the support medium used in the AFBR process appeared to be primarily dependent on a positive surface charge. Silanol groups were very effective for adsorption if inorganic materials were used for the support medium. Sewage could be efficiently treated, even at a hydraulic retention time of 6 h and at 15℃. Treating low-strength wastewater from a sugar-manufacturing plant in three stages, comprising anaerobic, aerobic, and activated carbon adsorption processes, resulted in an effluent with a quality comparable to that of tap water except for the inorganic carbon and conductivity. Middle-strength wastewater from a brewery could be more effectively treated by a two-stage AFBR than by a single-stage one. Sewage sludge was efficiently treated by a modified two-stage digestion process with liquefaction of thickened surplus sludge. The maximum volumetric loading rate of VSS in this process was two to three times higher than that of the conventional process. The VSS digestion efficiency also increased by around 10% compared to that in the conventional process at the same volumetric loading rate. Slurries containing 20% (v/v) coffee waste solids were treated anaerobically in two-phase thermophilic methane fermentation with slurry-state liquefaction. By repeated batchwise treatment, the degradation efficiency of coffee waste and the maximum gas evolution rate per total volume including the liquefaction increased to 70% and 1.43 l/l. d, respectively. High-strength wastewater with a high salt content from a pickled-plum manufacturer was also treated effectively in the AFBR after the wastewater was diluted more than five times. The red pigment in the wastewater was completely decolorized under all conditions examined. When five-fold-diluted shochu distillery wastewater without suspended solids, to which trace elements such as Ni^<2+> and Co^<2+> had been added, was treated in the AFBR, a maximum TOC volumetric loading rate of 42 g/l.d, with a TOC removal efficiency of 78%, was achieved. This rate was four times higher than that without the addition of the mineral nutrients, and corresponded to a BOD loading rate of 68 g/l.d. The problem of accumulation of NF_4^+ (about 1,000 mg/l)and propionic acid during methane fermentation was resolved by the utilization of residual propionic acid as an electron donor during the denitrification and nitrification reactions. Effluent was recycled from the nitrification reactor to the denitrification reactor to remove NH_4^+ and volatile fatty acids simultaneously. In conclusion, methane fermentation was found to be a highly efficient process for the treatment of a wide variety of effluents.
社団法人日本生物工学会の論文
1996-09-25

地球環境に優しい水処理技術としてのメタン発酵法の開発

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