Near-Complete Phosphorus Recovery from Challenging Water Matrices Using Multiuse Ceramsite Made from Water Treatment Residual (WTR)

Abstract

Water treatment residual (WTR) is a burden for many water treatment plants due to the large volumes and associated management costs. Here, we transform aluminum-salt WTR (Al-WTR) into ceramsite (ASC) to recover phosphate from challenging waters. ASC showed remarkably higher specific surface area (SSA, 70.53 m²/g) and phosphate adsorption capacity (calculated 47.2 mg P/g) compared with previously reported ceramsite materials (< 40 m²/g SSA and < 20 mg P/g). ASC recovered > 94.9% phosphate over a wide pH range (3 – 11) and generally sustained > 90% of its phosphate recovery at high concentrations of competing anions (i.e., Cl^-, F^-, SO₄^2-, or HCO₃^-) or humic acid (HA). We challenged the material with real municipal wastewater at 10℃ and achieved simultaneous phosphate (>97.1%) and COD removal (71.2%). Once saturated with phosphate, ASC can be repurposed for landscaping or soil amendment. Economic analysis indicates that ASC can be a competitive alternative to natural clay-based ceramsite, biochar, or other useful materials. Therefore, ASC is an eco-friendly, cost-effective adsorbent for phosphate recovery from complex waters, shedding light upon a circular economy in the water sector. Synopsis: Ceramsite made from aluminum-salt water treatment residual exhibited great capability of recovering phosphate from waters under challenging conditions.