Fig. 1. Soluble P in two water treatment residuals (WTRs) spiked with KH₂PO₄ solutions and incubated up to 42 d. Initial Langmuir phosphorus adsorption maximum (P_max) values were obtained using batch equilibration of WTR (<2 mm) with standard P solutions ranging from 0 to 100 mg P L^–1 for 17 h.