Phosphorus pollution comes from many sources, mainly sewage treatment plants, storm sewers, and industrial sources. Most of these are point sources.
In rural areas, the sources are sewage treatments from small towns, improper septic systems, storm sewers, manure runoff, nutrient runoff, milkhouse wastes, and eroded soil. Most of these are non-point sources, non-point sources make it extremely hard to pin point exactly where the phosphorus pollution is coming from or how it is getting there.