Technology for recovering phosphorus from incinerated wastewater treatment sludge

A bench-top study of phosphorus-recovering technology from ash associated with incinerated wastewater (sewage) treatment sludge was conducted by adding sulfuric acid to ashes for the elution of phosphorus. With the exception of lead, which is insoluble in sulfuric acid, when the pH of the ash fell below 2.0, phosphorus and various heavy metals in the ash were extracted. The study found that, when alkalis were added to adjust the pH of the ash extract to 4.0, phosphorus was subsequently recovered via filtration. Furthermore, when alkalis were added to adjust the pH to 10, the recovery of various heavy metals was observed. In addition, disposal of the remaining solution (wastewater), which consists of a relatively low concentration of salts, is not considered to be a significant issue since it is within wastewater discharge standards and has been found to be useful as an acid-treating substance.