Red, white, and green? Applying agricultural technologies to treat algal blooms

Abstract Summer often brings harmful algal blooms to ponds, lakes, and even the Lincoln Memorial Reflecting Pool. These blooms are caused by warm, shallow water with high levels of nutrients, especially phosphorus (P). Researchers from the USDA Agricultural Research Service developed phosphorus removal structures, called P‐Traps, to filter phosphorus from water before it fuels algae growth. Originally designed for agricultural drainage, this technology could also help clean urban ponds. Unlike current treatments that kill algae but leave nutrients behind, P‐Traps remove the phosphorus that causes blooms. Using the P‐Trap software, researchers evaluated scenarios using different filter materials and treatment times. They found that filtering a 4.5‐million‐gallon pond over 1 month offers a good balance between cost and performance. This case study shows that P‐Trap technology is flexible and could be used in many settings to reduce phosphorus pollution, improve water quality, and prevent future algal blooms.