Abstract
Several experiments were carried out in order to know whether or not vitamin B_<12> would be formed during aeration in the municipal activated sludge plant. Since much larger amount of vitamin B_<12> is contained in the sludge added as seed at the entrance of the aerator as compared with the vitamin presumably formed during aeration, it might be impossible to determine the amount of vitamin increased during the treatment. On the other hand, calculating from the amount and vitamin B_<12> content of activate sludge discharged and those of sewage entering into the plant, the presumably formed vitamin B_<12> is supposed to be the order of one tenth mμg per ml of sewage and the vitamin added as return sludge is in the order of one tenth μg. On the basis of this reduction, it is supposed to be impossible to determine by the microbioassay method the amount of the vitamin formed during aeration process experimentally.
