Phosphates (P)
Phosphates, just like natural nitrates, are an important nutrient in nature that leads to increased algae and plant growth when concentrations are too high. Since 1986 no more phosphate-containing detergents have been in use. As a result, the phosphate contamination in rivers and lakes has declined considerably. In small sewage treatment plants phosphate can be removed by adding a precipitant (discharge class + P).