Phosphorus (P) recovery is an important sustainability challenge because P is essential to agriculture, finite in its conventional mined form, and environmentally damaging when lost from managed systems. Struvite precipitation is one promising recovery pathway, but its broader use is constrained by magnesium (Mg) and nitrogen (N) input requirements. This thesis evaluated whether delivering Mg on biochar changes P removal behavior in a fluidized bed precipitation reactor system relative to conventional solution-phase Mg addition, and whether biochar feedstock type influences those outcomes. Treatments used synthetic urine as a controlled model wastewater and varied by Mg delivery mode, substrate type, and N quantity. P removal was assessed using comparisons of maximum observed removal. Pseudo-second-order linearization provided the better descriptive fit in 13 of 21 comparable replicates (1 first-order; 7 ties; 1 insufficient) and was therefore used as the working kinetic framework. At the treatment level, manure biochar treatments had the highest mean total Mg input (2.494 ± 1.812 g) and maximum observed P removal (98.617 ± 1.639%), whereas solution-phase Mg treatments had the lowest mean total Mg input (0.503 ± 0.136 g) and the lowest, most variable maximum observed removal (67.372 ± 33.067%). In the additive regression model predicting maximum observed P removal, solution-phase Mg was associated with lower removal relative to biochar-associated Mg (β = -34.52, p = 0.011), and wood substrate was associated with lower removal relative to manure (β = -23.97, p = 0.010). Total Mg input (p = 0.428) and total N available (p = 0.575) were not significant predictors. These findings suggest P removal was not explained by Mg delivery method alone, but instead reflected broader treatment contexts, including substrate, Mg input structure, and chemical environment. This work points to potential tradeoffs among removal extent and resource input in biochar-modified P recovery systems.