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Removing Phosphorus from Swine Wastewater

Storage tank (1) in background holds wastewater from which ammonia nitrogen and carbonate buffers have already been removed. This wastewater is pumped to reaction chamber (2) along with a slurry of water and hydrated lime suspended in mixing chamber (3). [More lime slurry is stored in a container (4) until needed.]

Liquid flows from the reaction chamber (2) into cone-shaped settling tank (5). There, phosphorus sludge settles to the bottom (6) and is later removed, filtered and dried in filter bags. Cleaned wastewater flows from top of settling tank via the white pipe (7) and is delivered to sump (8). Underground pipe carries cleaned wastewater to nearby subsurface irrigation system for crops.

This phosphorus separation module is installed on a hog farm in Duplin County, N.C.

U.S. Department of Agriculture