Chemical precipitation of struvite: Nutrients recovery in conic fluidized bed reactor using a low-cost industrial magnesia compound

Abstract

The physico-chemical process of struvite precipitation is a technique that demonstrates a high potential in nutrients recovery from different kinds of wastewaters. This study aimed to evaluate the use of a low cost industrial compound with high magnesia content as alternative reagent source of magnesium ions and alkalinity required for precipitation. It was a strategy to turn the process economically viable and reduce the chemical costs. Mg(OH)2 slurries were obtained and evaluated regarding the nutrients recovery from a synthetic wastewater rich in NH4+-N and PO43-P and the quality of the generated crystals with the identification of the mineral of interest – the struvite. The experiment was performed in laboratory scale using a conic fluidized bed reactor in a semi-continuous operation. The proper pH control (8.0–8.5) by the automated addition of Mg(OH)2 slurry allowed considerable PO43-P removal equal to 93.5%. The recovered solids from the process showed purity of approximately 84% of struvite.