過剰汚泥嫌気性消化における過硫酸カリウムまたは過硫酸陽極溶液を用いた酸生成の改善

Potassium ferrate (K₂FeO₄) has been widely applied as a pretreatment agent for residual sludge digestion, but the complete synthesis of its solid form is costly. In this study, the use of ferrate anode solution (FAS) was examined as a more economical alternative. FAS is generated as an intermediate byproduct during the electrolytic production of solid K₂FeO₄. The performance of FAS was compared with that of conventional solid K₂FeO₄ to assess their respective effects on anaerobic acid production and sludge dewatering. The results indicate that sludge soluble chemical oxygen demand (SCOD) was increased to 3807 mg/L at the low dosage of 10 mL/L, and the production of short-chain fatty acids (SCFAs) reached 2142 mg COD/L. At this dosage, higher efficiencies in protein and polysaccharide release were achieved compared with high-dose K₂FeO₄ (0.5 g/g TSS). Sludge settling and dewatering properties were also improved, and reductions of 9.1% in sedimentation ratio and 9.7% in cake moisture content were achieved during pretreatment. These findings suggest that FAS, as an intermediate byproduct, can replace solid K₂FeO₄ for sludge pretreatment because of its high efficiency at low dosages and its distinct enhancement of dewatering performance. FAS may therefore serve as a more economical and effective option.