Using Treatment Residuals TO REDUCE PHOSPHORUS in agricultural runoff

Drinking water treatment residuals can be beneficially used to reduce phosphorus (P) in runoff water from manured agricultural land. The objective of this study was to determine treatment residual components responsible for P sorption and reduction of P in runoff water. Using 21 aluminum‐ (Al‐) based treatment residuals from Oklahoma utilities, chemical components related to P sorption (amorphous Al [Alox, 1.33–48.7 g/kg], iron [Fe] [Feox, 0.23–7.44 g/kg] oxides), clay (0–100%), and water‐soluble calcium (0.05–0.74 g/kg) were measured. Linearized Langmuir P sorption maxima (Pmax) ranged from 0.30 to 5.14 g/kg, and nonlinear Freundlich P distribution coefficient (KP) ranged from 17.5 to 1,085 L/kg. Addition of water treatment residuals (50 Mg/ha) to box plots treated with poultry litter (16.7 Mg/ha) reduced runoff P by from 14.0 to 84.9%. Reductions in runoff P were strongly correlated (p < 0.05) with Pmax and Alox. Performance of treatment residuals as a P sorbent to reduce runoff P from manured land can be estimated from their Pmax or Alox content.