Isn't phosphate what we removed from our soaps, and still plagues us to this day by causing algal blooms and eutrofication?

There are many types of phosphorus minerals, and the differences in their chemistry is extremely important to how they behave in nature. Some dissolve readily in water, and some last for centuries in water.

An analogy may be helpful. Amber and cyanide are both compounds that contain carbon in them.

Amber is made from pure carbon tightly bonded together:

Cyanide is made from 50% carbon 50% nitrogen:

Both minerals contain carbon, but one takes minutes to dissolve in water, while the other takes millennia. Additionally, one is very toxic to people after it is dissolved, while the other is commonly worn as jewelry.

In the same manner, the phosphate compound that used to be commonly found in household cleaners was Tri-Sodium Phosphate or TSP.

The chemical formula for the apatite mineral used in the Anacostia River is:

Unlike TSP, apatite will last for millions of years, as can be evidenced from the fossil (bone-apatite) records of the earth. Many forms of apatite are also used as jewelry.

.