| abstract |
The wastewater treatment method includes, when raw water is subjected to an activated sludge treatment, performing a first sludge returning step: a step of returning sludge, which was previously aerated and stirred in a first excess sludge tank or sludge retention tank equipped with an aerator and a stirrer, to an treatment tank, a sequencing batch reactor or an anaerobic tank; an optional step of returning sludge, which was previously aerated and stirred in a second excess sludge tank or thickened sludge retention tank equipped with an aerator and a stirrer, to a treatment tank, a sequencing batch reactor or an anaerobic tank; and maintaining genus Bacillus bacteria in the treatment tank, the sequencing batch reactor or the anaerobic tank, to which the sludge has been returned, at 2.0×10 5 to 22.5×10 5 cfu/mL. |