Recovery of phosphate from municipal wastewater as calcium phosphate and its subsequent application for the treatment of acid mine drainage

Abstract

Here, the co-managment of municipal wastewater (MWW) and acid mine drainage (AMD) is proposed, where the recovered low-value phosphorus from MWW is used for the treatment of AMD. Specifically, MWW was treated using calcium hydroxide (Ca(OH)2), a low-cost and readily available material, with the ammonia content being greatly reduced (89%) through stripping and phosphates practically eliminated (>99%). The recovered low-value phosphorus material, in the form of calcium phosphate (Ca3(PO4)2), was then used for the treatment of AMD from coal mining. Metals contained in AMD scavenged phosphorous, forming new minerals, and the increased alkalinity led to their precipitation. The optimum treatment conditions were 90 min contact time, 10 g L−1 Ca3(PO4)2 dosage, and room temperature and ambient pH. Under these conditions, AMD's metal content (Fe, Mn, Cr, Cu, Ni, Pb, Al, and Zn) was practically depleted (>99% removal) and sulphate (SO₄) greatly reduced (90.6%). Results were underpinned by FTIR, FIB/SEM, EDS/SEM, XRF, and XRD. Overall, this indirect co-treatment method holds great promise for the sustainable management of both wastewater matrices and can provide a simple and effective solution for their co-management, particularly in the developing world context where it could also help in advancing the UN's sustainable development goals.