Removal of ammonia as struvite from anaerobic digester effluents and recycling of magnesium and phosphate

A second order kinetic model was developed to predict the rate and extent of removal as struvite from anaerobic digester effluents. Alternative to this, can be recovered from struvite and the remaining Mg2+ and can be recycled back to the wastewater to fix more . The solution was retained and the remaining Mg2+ and were returned back to be mixed with wastewater. In a five-step process, recovery was initially 92% and progressively decreased to 77% in the fifth stage, due to loss of Mg2+ and at each step in the supernatant. Finally, economic analysis of recycling nutrients was performed and compared to the one step process. The cost of recovery was calculated as $0.36/kg NH4-N which is lower than $7.7/kg NH4-N the cost of one step process without considering the market value of struvite obtained in one step process.