Phosphorus recovery as struvite from wastewater by using seawater, brine and natural brine

Struvite crystallization is a widely employed technique for phosphorus recovery from wastewater. The accessibility and availability of cost-effective magnesium alternatives pose challenges for this process. This paper is a comparative study of struvite precipitation from synthetic wastewater using seawater, brine and natural brine as a low-cost magnesium sources. The impact of initial pH and Mg/P molar ratio on phosphate recovery was assessed and compared with Visual MINTEQ to determine its suitability for simulating P removal efficiencies. For the three magnesium sources, the findings indicated an improvement in phosphate removal efficiency with higher initial pH and Mg/P molar ratio. Nonetheless, at lower pH values and Mg/P molar ratios, the model calculations yielded higher removal efficiencies than the experimental results, attributed to its inability to consider system kinetics. Additionally, the analysis of precipitates showed the concurrent precipitation of magnesium phosphates when using natural brine. The Ca/Mg molar ratio in brine affects the morphology and the purity of the crystal product. Overall, alternative magnesium ions collected from sebkhat Ezzemoul can be a potential candidate for sustainable phosphorus recovery from wastewater as well as seawater and brine. Further studies are recommended to control the product properties.