title: Steel slag filters to upgrade phosphorus removal in constructed wetlands: two years of field experiments.
abstract: Electric arc furnace steel slag (EAF-slag) and basic oxygen furnace steel slag (BOF-slag) were used as filter substrates in two horizontal subsurface flow filters (6 m(3) each) designed to remove phosphorus (P) from the effluent of a constructed wetland. The influences of slag composition, void hydraulic retention time (HRTv), temperature, and wastewater quality on treatment performances were studied. Over a period of almost two years of operation, the filter filled with EAF-slag removed 37% of the inlet total P, whereas the filter filled with BOF-slag removed 62% of the inlet total P. P removal occurred predominantly via CaO-slag dissolution followed by Ca phosphate precipitation. P removal efficiencies improved with increasing temperature and HRTv, most probably because this affected the rates of CaO-slag dissolution and Ca phosphate precipitation. It was observed that long HRTv (>3 days) can cause high pH in the effluents (>9) as a result of excessive CaO-slag dissolution. However, at shorter HRTv (1-2 days), pH values were elevated only during the first five weeks and then stabilized below a pH of 9. The kinetics of P removal were investigated employing a first-order equation, and a model for filter design was proposed.
authors.affiliation: L'UNAM Université, Ecole des Mines de Nantes, CNRS, GEPEA, UMR 6144, 4 rue Alfred Kastler, 44307 Nantes, France. cristian.barca@mines-nantes.fr
authors.forename: Cristian
authors.initials: C
authors.lastname: Barca
authors.forename: Stéphane
authors.initials: S
authors.lastname: Troesch
authors.forename: Daniel
authors.initials: D
authors.lastname: Meyer
authors.forename: Peter
authors.initials: P
authors.lastname: Drissen
authors.forename: Yves
authors.initials: Y
authors.lastname: Andrès
authors.forename: Florent
authors.initials: F
authors.lastname: Chazarenc
mesh_terms: D005374:Filtration / Q000379:methods; D007220:Industrial Waste; D010758:Phosphorus / Q000737:chemistry*; D013232:Steel / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
chemical_list: D007220:Industrial Waste; D014874:Water Pollutants, Chemical; D013232:Steel; D010758:Phosphorus