To provide an anaerobic treatment method capable of enhancing the decomposition rate of org. sludge to reduce sludge disposal cost and capable of enhancing the recovery rate of energy (the formation amt. of biogas such as methane).
Org. sludge is treated in an alkali treatment tank 2 and subsequently subjected to acid fermentation treatment. An alkali treatment process comprises a process for chemically solubilizing sludge under an alkali condition of pH 11 or more and an acid fermentation process comprises a process for biologically solubilizing sludge under a pH condition of 11 or less. The acid fermentation process pref. comprises a plurality of tanks 6, 7 different in pH and the pH of the first stage acid fermentation tank 6 is held to 9-11. Pref., separated sludge after anaerobic digestion and/or activated sludge is added to the first stage acid fermentation tank 6.
MIYA AKIKO
YONEYAMA YUTAKA
SUZUKI TAKAYUKI
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