The Des Moines-area sewage treatment plant plans to spend $19 million on a system that will pull much of the phosphorus from wastewater and turn it into fertilizer pellets to be sold to farmers, The Des Moines Register reported. Phosphorus is the key cause of large algae blooms in Iowa’s rivers and lakes. The state has been battling more frequent outbreaks of blue-green algae that emit toxins. Phosphorus also contributes to the summertime dead zone in the Gulf of Mexico, an area left with little oxygen after algae bloom and then consume oxygen when they die.