Effect of Calcium Ion on Sludge Characteristics

概要

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Concentratons of the metals in sewage sactivated sludge were examined over a period of one year. The sludge contained reatively large amounts of calcium (14-16 mg/g SS), aluminium (11-28 mg/g SS), and iron (11-30 mg/g SS). The relative contents of the metals in the sludge decreased in the following orger : Fe>Al>>Ca>Mg>Zn&Mn, etc.On the other hand, the solution of mixed liquor in the aeration tank contained relatively high concentrations of Ca^〓 (17-23 mg/l) and low concentrations of Mg^〓 (3-6 mg/l).Most of the calcium in sewage activated sludge was easily extracted with weak acid (pH 3).However, little iron and aluminium were extracted under the same conditions. Therefore, the acid-terated sludge was used to examine the effect of Ca^〓 on sludge characteristics. Wtih increaseing amounts of Ca^〓 added, 30-min settled sludge volume and the turbidity of the supernatant after 30-min settling decreased. The maximum amount of Ca^〓 bound to the acid-treated sludge was nearly equal to the amount of Ca^〓 extracted by the acid treatment.These results indicated that Ca^〓 binds to sludge surface materials and plays an important role not only in flocculation in sewage activated sludge but also in determining sludge characteristics such as thickness.
社団法人日本生物工学会の論文
1985-06-25