Circular Economy: Finding phosphorus in wastewater

Eutrophication is a big word, and it represents a big problem. It occurs when rivers and lakes reach an overabundance of nutrients – most often from agricultural and water treatment practices. This overabundance of nutrients increases algae growth, setting off an ecosystem chain reaction that can have consequences for all plant and animal life.

To prevent eutrophication of freshwater systems, wastewater treatment plants must remove phosphorus from treated water. But phosphorus is a finite resource for which there is no known substitute. In fact, the United Nations predicts global demand for phosphorus will rise 70 percent by 2050. 

So instead of removing it, why not extract and reuse it? 

The process is based on fluidized bed technology in which phosphorus and nitrogen are recovered from wastewater by directing the wastewater through a separate reactor. Here, magnesium salt and air are added. The resulting precipitation process refines the phosphorus, discarding heavy metals and environmentally unfriendly substances. 

The outcome is a granulate that contains phosphorus, nitrogen, and magnesium. The struvite is precipitated as a ‘ready-to-use fertilizer’ and sold to agriculture.