Phosphorus sorbing materials: sorption dynamics and physicochemical characteristics.

The effectiveness of various management practices to reduce phosphorus (P) loss from soil to water can potentially be improved by using by-product materials that have the capacity to sorb phosphorus. This study evaluated the P sorption and desorption potential, and the physicochemical characteristics of various phosphorus sorbing materials. Twelve materials were selected and P sorption potentials ranged between 66 and 990 mg kg(-1). Iron, and calcium drinking water treatment residuals (DWTRs), a magnesium fertilizer by-product, aluminum, and humate materials all removed substantial amounts of P from solution and desorbed little. Humate had the highest maximum P sorption capacity (S(max)). Materials which had a low equilibrium P concentration (EPC(0)) and a high S(max) included aluminum and humate by-products. In a kinetic study, the Fe-DWTR, Ca-DWTR, aluminum, and magnesium by-product materials all removed P (to relatively low levels) from solution within 4 h. Phosphorus fractionation suggests that most materials contained little or no P that was readily available to water. Sand materials contained the greatest P fraction associated with fulvic and humic acids. In general, materials (not Ca-DWTR) and magnesium by-product were composed of sand-sized particles. There were no relationships between particle size distributions and P sorption in materials other than sands. The Ca- and Fe-DWTR, and magnesium by-product also contained plant nutrients and thus, may be desirable as soil amendments after being used to sorb P. Further, using Ca-DWTRs and Fe-DWTRs as soil amendments may also increase soil cation exchange and water holding capacity.

Optimization of low-cost phosphorus removal from wastewater using co-treatments with constructed wetlands.

Eighteen wastewater treatment systems were operated for one year to investigate phosphorus (P) removal. Systems paired co-treatment reactors containing iron or calcium drinking water treatment residuals with vertical-flow constructed wetland mesocosms planted with Schoenoplectus tabernaemontani (K.C. Gmel.) Palla. For secondary municipal wastewater, soluble reactive P (SRP) concentrations were reduced from 0.70 to 0.03 mg L(-1) (95%) or 0.01 mg L(-1) (98%) by systems with the calcium or iron co-treatments, respectively (compared to 0.09 mg L(-1) or 87% by controls). Total P (TP) concentrations were reduced from 1.00 to 0.07 mg L(-1) (93%) and 0.05 mg L(-1) (95%) by the same treatments (compared to 0.16 mg L(-1) or 84% by controls). For anaerobically digested dairy wastewater, SRP was reduced from 7.68 to 6.43 mg L(-1) (16%) or 5.95 mg L(-1) (22%) by the systems with calcium or iron, respectively (compared to 7.37 mg L(-1) or 4% by controls). For this wastewater, the TP was reduced from 48.5 to 22.5 mg L(-1) (53%) and 22.7 mg L(-1) (53%) by the same treatments (compared to 24.1 mg L(-1) or 50% by controls) but performance improved substantially with a design modification tested.