Abstract
To effectively use sewer system resources, experiments were carried out to recover phosphorus and aluminum from incinerator ash of sewage sludge. I found that, if an alkali solution is added to sewage ash, phosphorus and aluminum can be selectively eluted to the solution and separated by adding calcium hydroxide. Phosphorus and aluminum were recovered in the form of calcium phosphate and sodium aluminate respectively. The recovered phosphorus compound was 100% citric acid-soluble, and contained 36% phosphoric acid. With respect to toxic heavy metals specified by the Fertilizer Control Law, the Cd and As contents were below the specified standards, and Ni, Cr, Pb and Hg were not detected in the available chemical analyses. The recovered phosphate was of acceptable quality for use as fertilizer. The recovered aluminum solution contained 17000mg/1 Al, and may be used as flocculant in the removal of phosphorus from sewage.
