Removal of NH4-N by struvite precipitation: A Review and Study on MAP Process at Laboratory Scale

Abstract

This study was conducted on the MAP process to improve struvite precipitation and more efficient removal of NH4-N from the wastewater. MAP process is one of the innovative Physicochemical process which can majorly contribute for the removal of NH4-N by forming the struvite complex under required condition. In order to meet stringent discharge standards for NH4-N, an experimental work was carried out focusing the general problem of effluent discharge for the industries of India containing high NH4-N stream. For this we evaluated the effort of feeding sequence of precipitating reagent (lime, flocculent, magnesium and phosphate) for NH4-N removal by forming MAP i.e. struvite deposit keeping calcium interference in mind. Various studies reviewed which effectively precipitate struvite by an addition of excess magnesium and phosphate sources with different stoichiometric ratios. The stoichiometric calculation for the optimized dosage of reagent makes the precipitation more efficient. Different stoichiometric ratio were tested to determine the required Mg2+ and PO4 3+ concentration for maximum NH4-N removal by keeping NH4 + constant for the effluent.