凝集沈殿による下水中のリン回収とリン含有凝集沈殿汚泥の植物根分泌酵素有機酸による可溶化

抄録

The most important nutrient elements required for food production by crops are nitrogen, phosphorus and potassium. Among these elements, however, amount of rock phosphorus remained in the world is limited. Therefore, it is important to develop the technology and construct the social system for recycling use of phosphorus. Municipal wastewater contains phosphorus of 5-10 mg/l as the suspended and soluble forms. This paper deals with the separation of phosphorus from municipal wastewater by the coagulation/flocculation/sedimentation process using a jet mixed separtor (JMS) which is a simple but effective solid-liquid separtor. A new coagulant, Poly Silicato Iron (PSI), was used together with polyaluminum chloride and FeCl₃. The PSI has a molar ratio of Fe to Si with 1: 1 to 1: 5 anda molecular weight of 200, 000 to 500, 000 Da. The JMS removed about 80% phosphorus with the addition of 5 mg Al or Fe/l. Classification of phosphorus forms in the coagulated sludge was carried out, and the effectiveness of the acid phosphatase and citric acid secreted from the plant roots for releasing orthophosphate from the organic and inorganic phosphorus compounds contained in the sludge was examined. It was shown that the inorganic phosphorus coagulated by FeCl₃, and organic phosphorus in the sludge released orthophosphates by the acid phosphatase.