Abstract: Various embodiments disclosed relate to removal of phosphorus from water using magnesium or calcium. A method of removing phosphorus from water including magnesium, calcium, or a combination thereof. The method includes forming a precipitate in the water including the phosphorus and the precipitation composition. The precipitate includes a salt that includes the phosphorus, and also includes magnesium, calcium, or a combination thereof. The method also includes removing the precipitate including the phosphorus from the water including the precipitate, to form water having a lower dissolved phosphorus concentration than the water including phosphorus that was combined with the precipitation composition. The method can include combining the water including phosphorus and a precipitation composition including a magnesium salt, a calcium salt, or a combination thereof.