し尿汚泥焼却灰の化学組成とリン溶出について

抄録

In a project to recover phosphorus from night soil, a possible phosphorus resource, composition of major components and toxic substances, and phosphorus together with its chemical form were determined in night soil sludge incineration ash at 14 facilities in Ehime prefecture.
The composition of major components were Al₂O₃, P₂O₅, SiO₂, Fe₂O₃, CaO, MgO Na₂O and K₂O in decreasing order with little seasonal variation. The average phosphorus concentration was about 23.9 wt% calculated as P₂O₅ and was higher than that of sewage sludge incineration ash. It was found that the concentration of Cd was higher than that in sewage sludge incineration ash but the concentration of toxic substances including Cr, Pb, As, Se and Hg were lower than those in sewage sludge incineration ash.
By X-ray diffraction analysis, it was found that major mineral of night soil sludge incineration ash was phosphate mineral and the average concentration of 14 facilities was 42 wt%. Four species of phosphate mineral were identified, and the concentration of aluminum calcium phosphate was the highest in them. It was thought that in view of included phosphate minerals, acid extraction method was more effective than alkali extraction method．About 80 % of phosphorus was eluted by adding sulfuric acid to pH 2.2.
The significant equation to estimate the recoverable phosphorus quantity from each quantity of night soil and septic tank sludge was obtained by multiple regression analysis.