鉄系凝集剤が活性汚泥の呼吸活性へ及ぼす影響

抄録

In order to remove phosphorus or control bulking, coagulants are sometimes added into the activated sludge process. Fe salts and Al salts are usually used as coagulant because they empirically have no influence on the removal efficiency. However, precise influences of coagulants on the respiratory activity of the activated sludge have not been clear yet. Firstly, the measurement method of dehydrogenase activity was discussed in this paper. Secondly, the influence of shock load of ferric chloride on the respiratory activity of the activated sludge was discussed from the batch experiments by measuring dehydrogenase activity and oxygen uptake rate.
The respiratory activity of the activated sludge decreased with ferric chloride addition. Decrease of pH, increase of Cl- concentration and increase of Fe concentration were suggested to decrease respiratory activity. The effect of increase of Cl^- and Fe concentration was found to be negligible at actual condition. However, respiratory activity was sensitive to the change of pH and it was decreased rapidly with decrease of pH. It is necessary to prevent the decrease of pH value by alkalinity addition in order to maintain the respiratory activity.