Ligand-Enabled Donnan Dialysis for Phosphorus Recovery from Alum-Laden Waste Activated Sludge

• Published in: Environmental science & technology 2022-10, Vol.56 (19), p.13945-13953
• Main Authors: Shashvatt, Utsav, Amurrio, Fabian, Blaney, Lee
• Format: Article
• Language: English
• Subjects: Acetic acid; Activated sludge; Citric acid; Dialysis; Edetic acid; Ethylenediaminetetraacetic acids; Hemodialysis; Ligands; Liquid wastes; Orthophosphate; Oxalic acid; Phosphorus; Recovery; Sludge; Sodium chloride; Solid wastes; Solubilization; Treatment and Resource Recovery; Waste management; Waste streams
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.2c02153

While many nutrient recovery technologies target liquid waste streams, new strategies are required for effective phosphorus recovery from solid waste. This study reports an innovative ligand-enabled Donnan dialysis process to recover orthophosphate (P­(V)) from alum-laden waste activated sludge (WAS). Four ligands, namely acetate, citrate, ethylenediaminetetraacetate (EDTA), and oxalate, were evaluated for P­(V) release from a synthetic sludge containing 5 mM P­(V) and 25 mM Al­(III) and a real, alum-laden WAS with similar contents. Citrate and EDTA released more than 95% of P­(V) at doses of 30 mM, outperforming acetate and oxalate. The ligand-based solubilization strategy was coupled with Donnan dialysis to recover P­(V) into a clean sodium chloride draw solution. After Donnan dialysis with the synthetic sludge, the P­(V) recovery’s order was as follows: EDTA (54.4%) > citrate (41.7%) > oxalate (4.3%). The P­(V) recovery efficiencies were slightly lower for Donnan dialysis with real, alum-laden WAS, namely 45.1% and 25.2% for EDTA and citrate addition, respectively, due to competitive effects exerted by other dissolved species. These promising results successfully demonstrated the proof-of-concept for ligand-enabled Donnan dialysis.