Recovery of Phosphorus Using a Low-Grade Magnesium Oxide (Industrial By-Product) as an Alternative Magnesium Source. The MAGNYFOS Project.

Abstract

The MAGNYFOS project aims to use of magnesium by-product for the recovery of phosphorous in wastewater treatment plants (WWTPs) by the precipitation of struvite. This national project has developed and optimised laboratory-scale operating conditions for the concentrate streams of different treatment plants, a pilot-scale experimental phase was done to improve hydraulic and design conditions and the process modelling is being adjusted and validated with the experimental results. The three phases have been essential to understand and validate the struvite precipitation process, using a by-product that is 10 times cheaper than MgCl2. Furthermore, agricultural application trials are also being carried out with some of the products obtained. The main results show that it is possible to achieve up to 80% of phosphorus recovery with the molar rate P:Mg 1:2, phosphorus is recovered as struvite when the calcium concentration is low and the struvite content in the precipitate is greater than 75%.