Enhanced phosphorus bioavailability and heavy metal removal from sewage sludge ash through thermochemical treatment with chlorine donors

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Direct application of sewage sludge ash (SSA) to agriculture is mostly prohibited due to its heavy metals and limited bioavailability. Thermochemical treatment of SSA with Cl-donors were carried out to remove heavy metals and enhance P bioavailability. MgCl<SUB>2</SUB> and CaCl<SUB>2</SUB> removed more heavy metal than other Cl-donors. Pb was completely removed followed by Cd, Zn, Cu. They also increased P bioavailability by the conversion of Al–P to Ca/Mg–P which was confirmed by chemical fractionation. XRD confirmed the conversion of AlPO<SUB>4</SUB> to Ca<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>Cl, Ca<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>, and Mg<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> by the thermochemical treatment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thermochemical treatment of SSA was performed to remove heavy metals and enhance P bioavailability. </LI> <LI> CaCl<SUB>2</SUB> and MgCl<SUB>2</SUB> were effective Cl-donors for heavy metal removal. </LI> <LI> MgCl<SUB>2</SUB> increased P bioavailability of SSA by 53%. </LI> <LI> Thermochemical conversion of Al–P to Ca/Mg–P was confirmed by XRD and chemical fractionation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>