Effluents from both cells of a two-cell anaerobic lagoon system treating flushed swine waste from the University of Missouri Swine Farm were treated in parallel constructed wetlands – submerged flow (SF) and free water surface (FWS). Reductions in magnesium, ammonium, and total phosphorus ion concentrations in the wetlands were measured and used to calculate ion activity products (IAP) for struvite and compared to struvite solubility products (Ksp). Comparison of IAPs with Ksps indicated that the wetlands reduced the potential for struvite formation by 54 to 70%. The reductions were largely due to ammonium losses from the wetlands.