To decrease the addition of a flocculant, to diminish the the generation of sludge and to prevent the inhibition of methane fermentation at the time of treating org. waste in the treating system having a biological treating stage and an anaerobic fermentation stage.
A part of the excess sludge 5a generated in a biological treating stage #3 is introduced into an anaerobic fermentation stage #5 and transferred to an aerobic nitrification stage #6 along with digestion sludge 8, hence phosphorus is ingested by the facultative anaerobe contained in the excess sludge 5a, and the excess sludge 11 contg. the facultative anaerobe is separated. As a result of such biological dephosphorization, the addition of a flocculant in the subsequent stage of the anaerobic fermentation stage #5 and the generation of sludge are reduced, and fermentation is not inhibited by the returned flocculant.
MORO MASASHI
YAMAMOTO TETSUYA
SHIBATA TOSHIYUKI
