Recovery of phosphorus and nitrogen from domestic wastewater by using dolomite rock through struvite precipitation

Recovering essential nutrients like phosphorus (P) and nitrogen (N) from domestic wastewater is not only feasible but also required for sustainable nutrient management. This study investigated the potential of dolomite rock, a low-cost and environmentally friendly resource abundant in Ethiopia, to facilitate nutrient recovery through struvite precipitation. Dolomite was dissolved in 2M hydrochloric acid at a solid-to-liquid ratio of 25% to release magnesium ions, which were then mixed with wastewater in varying ratios at a controlled pH of 8.The initial wastewater composition contained the following elements: calcium (Ca²⁺) 32.1 mg/L, magnesium (Mg²⁺) 21.9 mg/L, sodium (Na⁺) 66.2 mg/L, potassium (K⁺) 11.8 mg/L, phosphate (PO₄³⁻-P) 1.65 mg/L, and ammonium nitrogen (NH₄-N) 19.4 mg/L. The composition of the filtrate changed dramatically when struvite precipitation was carried out with a wastewater-to-dolomite ratio of 50:70 mL. Following precipitation, the levels of calcium (Ca²⁺) rising to 748 mg/L, magnesium (Mg²⁺) falling to 0.61 mg/L, sodium (Na⁺) rising to 195.8 mg/L, and potassium (K⁺) falling to 1.9 mg/L. In contrast to ammonium nitrogen (NH₄-N), which was successfully reduced to 2.18 mg/L with a recovery rate of 88.75%, phosphate (PO₄³⁻-P) was surprisingly totally eliminated (100% recovery).The result shows that dolomite-induced struvite precipitation is an effective method for recovering nutrients from wastewater offering an alternative to conventional synthetic fertilizers. This approach not only mitigates environmental pollution caused by nutrient-rich wastewater but also provides a pathway for producing eco-friendly fertilizers. By utilizing locally available resources, this research contributes to cost-effective nutrient management and promotes sustainable agricultural practices.