Reactive cement pellet media including drinking water treatment and mine drainage residuals for phosphorus removal in agricultural runoff

Soil phosphorus (P) losses through agricultural runoff and tile drainage can lead to eutrophication of water resources. Drinking water treatment residual (DWTR) and acid mine drainage residual (AMD) have the ability to remove P but lack mechanical strength and a uniform particle size. Previous studies of DWTR and AMD consisted primarily of batch trials and measurement of P removal using flow-through columns, utilizing real agricultural runoff, would be beneficial to scalability. We modified DWTR and AMD through pelletization and pyrolysis and evaluated P removal using flow-through columns under different conditions (i.e. retention time, pH, and agricultural runoff). Pyrolysis increased P removal of the media pellets 2 to 17-fold. Filter media performance benefited from longer retention times and P removal efficiency increased 8-134% when retention time was increased from 1- to 5- min. Cost estimate and practicality for field deployment in a constructed pond wetland system were evaluated for each media. Cement binder + pyrolysis (CEM-P), cement binder (CEM), cement binder + DWTR + pyrolysis (RCB-P), and cement binder + AMD (ACB) were the most practical media for field deployment. The top 3 least costly media were CEM-P ($1,936), cement binder + AMD + pyrolysis (ACB-P; $2,159), and CEM ($2,809).