FUNDAMENTAL STUDY ON PHOSPHORUS RECOVERY FROM SEWAGE SLUDGE INCINERATION ASH BASED ON ACID EXTRACTION

Abstract

 This study dealt with phosphorus recovery based on acid extraction from sewage sludge incineration ash combining inorganic chemicals with solid-liquid separation. The recovery of iron and aluminum was also investigated. The recovery method consisted of three steps: after the acid extraction, the acid-extracted solution was adjusted to the pH of 3.0, 3.5, 4.0 or 5.0, and finally separated into calcium phosphate, iron hydroxide and aluminum solution fractions. The phosphorus recovery efficiency of 69-82% was obtained in the calcium phosphate fraction, and the efficiency reached a maximum at the pH of 4.0. The recovery efficiency of iron and aluminum was 55-90% and 75-82%, respectively. The calcium phosphate obtained had a sufficiently low content of heavy metals, but the purity and concentration of iron and aluminum obtained in each faction were evaluated to be insufficient.