Major sources of nitrate and phosphate are fertilizer, sewage and runoff from animal farms. Phosphate also comes from the erosion of phosphate-bearing soil and sediment during human land-altering activities such as construction and mining.

Where do nitrates come from?

Nitrate is a chemical found in most fertilizers, manure, and liquid waste discharged from septic tanks. Natural bacteria in soil can convert nitrogen into nitrate. Rain or irrigation water can carry nitrate down through the soil into groundwater.

What causes nitrates and phosphates?

The top sources are fertilisers, fossil fuel burning, sewage and treating drinking water –– sources which will increase as the population rises. Warmer summers, changing rainfall patterns and reduced river levels may mean higher concentrations of nitrates and phosphates in the water environment.