title: Suspended Sediment and Phosphorus Removal in a Woodchip Filter System Treating Agricultural Wash Water.
abstract: Woodchip filters have received attention in recent years for their ability to sustain denitrification activity across multiyear time frames. However, in some freshwater aquatic ecosystems, P rather than N is the nutrient considered most responsible for eutrophication. Previous studies have indicated that woodchip filters have limited ability to remove dissolved P, but in agricultural terrain, P export in watercourses is often dominated by particulate P (PP). Woodchip media, because of their high porosity and permeability and the surface roughness of the particles, could be effective for PP removal. In this study, we tested a woodchip filter for its ability to remove suspended sediment and associated PP at a farm in southern Ontario, Canada, where vegetable wash water with extremely high total suspended solids (TSS) was generated. The treatment system consisted of a 12.3-m concrete sedimentation tank and a slightly larger woodchip filter (16.1 m) installed in a subsurface trench. During 7 mo of full-scale operation, treating 10.8 m d, the filter system removed 71% of influent total P (TP) averaging 8.8 mg L and 99% of TSS averaging 5800 mg L, with most of the removal occurring in the tank and a lesser amount (6-16%) occurring in the woodchip filter. Almost all of the TP removal was associated with PP (91% removal) because dissolved P, averaging 1.5 mg L in the wash water, was little changed. Woodchip filters, when coupled with a solids settling tank, have the potential to provide high-capacity, low-maintenance treatment of suspended solids and associated particulate P in turbid waters.
authors.forename: Tahina
authors.initials: T
authors.lastname: Choudhury
authors.forename: Will Dean
authors.initials: WD
authors.lastname: Robertson
authors.forename: Darryl S
authors.initials: DS
authors.lastname: Finnigan
mesh_terms: D000383:Agriculture; D002170:Canada; D058440:Denitrification; D005374:Filtration; D010758:Phosphorus / Q000032:analysis*; D018508:Water Purification; D014934:Wood
chemical_list: D010758:Phosphorus