The Chemical Change of the Ash Components through Phosphorus Recovery of Dehydrated Sludge by Incineration using Alkali Metal Compounds

Abstract

In order to recover phosphorus from the wastewater sludge, the dehydrated sludge was mixed with the reagent of NaOH, KOH or Na 2 CO 3 , and incinerated at 750 °C or 900 °C. Phosphorus in the incinerated ash of the sludge was dissolved by the addition of the hot water, and recovered by the evaporation of the extract. The recovered phosphorus was confirmed to be an alkali metal phosphate, and the recovery rate reached about 75% regardless in these reagents (NaOH, KOH or Na 2 CO 3 ). The chemical change of the ash components were also found through phosphorus recovery.