Removal of nitrogen and phosphate from wastewater by addition of bittern

Removal of nitrogen and phosphate through crystallization of struvite (MgNH4PO4 · 6H2O) has gained increasing interest. Since wastewaters tend to be low in magnesium relative to ammonia and phosphates, addition of this mineral is usually required to effect the struvite crystallization process. The present study evaluated the feasibility of using bittern, a byproduct of salt manufacture, as a low-cost source of magnesium ions. High reaction rates were observed; the extent of nitrogen and phosphorus removals did not change beyond 10 min. Phosphorus removals from pure solutions with bittern added were equivalent to those obtained with MgCl2 or seawater. Nitrogen removals with bittern were somewhat lower than with the alternate Mg2+ sources, however. Application of bittern to biologically treated wastewater from a swine farm achieved high phosphate removal, but ammonia removals were limited by imbalance in the nitrogen:phosphorus ratio.