title: Using flue gas desulfurization gypsum to remove dissolved phosphorus from agricultural drainage waters.
abstract: High levels of accumulated phosphorus (P) in soils of the Delmarva Peninsula are a major source of dissolved P entering drainage ditches that empty into the Chesapeake Bay. The objective of this study was to design, construct, and monitor a within-ditch filter to remove dissolved P, thereby protecting receiving waters against P losses from upstream areas. In April 2007, 110 Mg of flue gas desulfurization (FGD) gypsum, a low-cost coal combustion product, was used as the reactive ingredient in a ditch filter. The ditch filter was monitored from 2007 to 2010, during which time 29 storm-induced flow events were characterized. For storm-induced flow, the event mean concentration efficiency for total dissolved P (TDP) removal for water passing through the gypsum bed was 73 ± 27% confidence interval (α = 0.05). The removal efficiency for storm-induced flow by the summation of load method was 65 ± 27% confidence interval (α = 0.05). Although chemically effective, the maximum observed hydraulic conductivity of FGD gypsum was 4 L s(-1), but it decreased over time to <1 L s(-1). When bypass flow and base flow were taken into consideration, the ditch filter removed approximately 22% of the TDP load over the 3.6-yr monitoring period. Due to maintenance and clean-out requirements, we conclude that ditch filtration using FGD gypsum is not practical at a farm scale. However, we propose an alternate design consisting of FGD gypsum-filled trenches parallel to the ditch to intercept and treat groundwater before it enters the ditch.
authors.affiliation: USDA-ARS, University Park, PA 16802, USA. ray.bryant@ars.usda.gov
authors.forename: Ray B
authors.initials: RB
authors.lastname: Bryant
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Buda
authors.forename: Peter J A
authors.initials: PJ
authors.lastname: Kleinman
authors.forename: Clinton D
authors.initials: CD
authors.lastname: Church
authors.forename: Louis S
authors.initials: LS
authors.lastname: Saporito
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: Folmar
authors.forename: Salil
authors.initials: S
authors.lastname: Bose
authors.forename: Arthur L
authors.initials: AL
authors.lastname: Allen
mesh_terms: D000383:Agriculture; D002133:Calcium Sulfate / Q000737:chemistry*; D005374:Filtration / Q000295:instrumentation*; D015386:Hazardous Substances / Q000032:analysis; D019216:Metals, Heavy / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D015386:Hazardous Substances; D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D002133:Calcium Sulfate