If I might add something, phosphates are in fertilizers and dish/laundry soaps. Treatment of wastewater doesn't require removal of these compounds, so they accumulate in the water. This is evident by "foam" whenever water is agitated, like waves or discharges from lakes. Our college chemical engineering classes visited wastewater treatment facilities and up river from the discharge it looked like any normal river. However, at and downstream the water was lime green from the blooms caused by phosphates. I've even used Google Earth and zoomed in on it and it's visible. Something you might try yourselves even. I've even read that now they claim BG algal blooms create a very hefty portion of the O2 in the atmosphere