Waste bones ash as an alternative source of P for struvite precipitation

•Fish bone ash contains higher amount of phosphorus than chicken and cow bone ashes.•Phosphorus was extracted from ash by acidic leaching using sulfuric acid.•Mg-P solution improved the reactivity of MgO.•Applying Mg-P solution for NH4-N recovery resulted with high-purity struvite.

Struvite precipitation has been widely applied for the removal of ammonium-nitrogen (NH4-N) from wastewater. Due to the high cost of phosphorus (P) reagents, the current research trend was directed to find alternative sources of P, in order to maintain a sustainable NH4-N removal process. The current study investigated waste bones ashes as alternative sources of P. Different types of bones' ashes were characterized, in which the ash produced from waste fish bones was the highest in P content (17%wt.). The optimization of the factors affecting P extraction from ash by acidic leaching showed that applying 2M H2SO4 and 1.25 kg H2SO4/kg ash achieved the highest P recovery (95%). Thereafter, the recovered P was successfully used in struvite precipitation, which achieved more than 90% NH4-N removal and high purity struvite.