An innovative 2-stage process for the recovery of phosphorus and recycling of ferric from ferric sludges generated in water and wastewater treatment

Ferric salts are used extensively in wastewater treatment to precipitate P, and as coagulant in water treatment. In all cases, large amounts of ferric sludge are produced. The ongoing chemical supply and sludge disposal represent a major operating cost to the water industry. A novel 2-stage process for Fe and P recovery from ferric phosphate sludge has been developed to enable the on-site recycling of ferric for such applications. In Stage I, PO4 is released in solution after the addition of a sulfide solution to initiate FeS precipitation. In Stage II, FeS is electrochemically oxidised to elemental sulfur that is deposited on the anode and generates a low-pH Fe solution for reuse. Simultaneously the cathodic reduction of sulfur forms sulfide, which can be reused in Stage I to create a fully integrated process...