Alkaline Leaching of Phosphate from Sewage Sludge Ash
The alkaline technology has been applied to phosphate (Pi) recovery from sewage sludge ash (SSA) at wastewater treatment plants (WWTP). Pi is extracted from mono-incinerated sewage sludge with NaOH and recovered from the leachate using chemical precipitation with Ca(OH)2. Approximately 30–40% of Pi could be recovered from SSA as calcium Pi while minimizing the leaching of toxic heavy metals at high pH. The recovered P product can be recycled as a fertilizing material for agriculture.