Essays of phosphorus recovery into struvite from fertilizer industry effluents

Abstract

The studied Fertilizer industry effluent contains high concentration of phosphorus in the range of 228–1025 mg L⁻¹, It is discharged in the surrounding sea without any preliminary treatment. Therefore, it constitutes a source of pollution to the coastal environment. This effluent contains also an important fluoride concentration. This quantity of phosphorus could be used to produce phosphorus fertilizer. So, the objective of this study was (i) to minimize fluoride concentration in fertilizer industry effluent and (ii) to recover phosphates from this effluent into the form of struvite (magnesium ammonium phosphate). To force the formation of struvite, ion was added by using ammonium chloride (NH₄Cl). A preliminary study showed that fluorides were transferred into solid phase at pH 4. At this value of pH, the degree of fluoride recovery amounted to 95.62%. In the second stage, experiments were conducted to examine the effects of pH and N/P molar ratio on the removals of and by forming struvite. The results show that the optimum pH value for struvite precipitation is in the range of pH 9–10, and the best phosphate and ammonium removal efficiency was observed to be 98 and 70.7%, respectively. Furthermore, it has been noted in the previous studies that phosphate and ammonium removal was affected by the amount of added ammonium and it was stated that 99.21% of total phosphate was removed when N/P molar ratio was 2 at pH 9.

Keywords:

• Wastewater
• Fertilizer industry
• Phosphorus
• Struvite
• Fluoride

Acknowledgements

This study was supported by PC2E (Pole of competences on Water and Environment) and the European project SOWAEUMED (Network in Solid Waste and Water Treatment between Europe and Mediterranean Countries, contract No. 245843).