Final answer:
The combination of soluble phosphorus with iron to form an insoluble compound is an example of chemical precipitation, leading to the formation of phosphate minerals. This process is used in wastewater treatment to control phosphorus levels and prevent eutrophication in natural water bodies.
Step-by-step explanation:
The process by which soluble phosphorus combines with iron to form a compound that is no longer useable by organisms is an example of chemical precipitation or specifically, the formation of a phosphate mineral that is insoluble and not readily available to organisms.
In natural ecosystems and during wastewater treatment, an abundance of phosphate can lead to excess algae growth, creating a negative impact on water quality and marine life due to lowered oxygen levels. When soluble phosphorus binds with iron or other metals, the resulting compound precipitates out of the water, becoming part of the sediment and thus not easily accessible to living organisms.