Fundamental Study on Improved Phosphorus Recovery from Sewage Sludge Incinerated Ash
髙島, 正信Takashima, Masanobu
In this study, improved methods of acid extraction and alkali extraction were proposed and examined for efficient recovery of phosphorus from sewage sludge incinerated ash. In the acid extraction method, iron phosphate was chosen to precipitate phosphate from the acid extraction solution, and EDTA was added to keep heavy metals soluble. The experimental results showed that 91-100% of phosphorus was recovered as iron phosphate. Also, the EDTA addition decreased the heavy metal content in the precipitate, but its effect appears to be limited. In the alkali extraction method, 55% of phosphorus was extracted by the conventional method using 0.1M NaOH at 70oC. Carbon dioxide was applied to the alkali treated ash, and dissolved 24% of phosphorus. Thus, phosphorus recovery was increased to a total of 79% from the sewage sludge incinerated ash by the improved alkali method.