title: Trace metal speciation and fluxes within a major French wastewater treatment plant: impact of the successive treatments stages.
abstract: Seven metals (Cd, Co, Cr, Cu, Fe, Ni and Pb) were monitored at the Seine-Aval wastewater treatment plant during 6 sampling campaigns in April 2004. Particulate and dissolved metals have been measured in 24h composite samples at each treatment stage (primary settling, secondary activated sludge and tertiary flocculation by FeCl(3)). In addition, the diffusive gradient in thin film technique (DGT) was used to determine the dissolved inert and labile metal fraction. Although all treatment stages were able to decrease particulate metals concentrations in wastewater, most dissolved metals concentrations were mainly affected during primary settling. This unexpected result was attributed to tertiary sludge filtrate recirculation. Metals added via the FeCl(3) reagent at the tertiary treatment were shown to lower the overall Cr removal from wastewater and to enrich Ni in effluents. The plant operating conditions (recirculation and reagent addition) appear therefore as important as treatment processes for the metals removal. Total metal fluxes were highly decreased by the whole treatment plant for Cd, Cr, Cu and Pb and to a lesser extend for Co and Ni. However, the labile metal fluxes were poorly decreased for Cu (18%), not significantly decreased for Ni and increased for Fe. The labile fraction of Cd, Co and Cr was not detectable at any stage of the plant. Discharged labile fluxes, at least for Ni, were potentially significant compared to the labile metal fluxes in the river measured downstream the plant. Treated urban wastewater discharges should be carefully considered as a possible source of bioavailable trace metals.
authors.affiliation: Cemagref, UR Hydrosystèmes et Bioprocédés, parc de Tourvoie, BP 44, 92163 Antony cedex, France.
authors.forename: Rémy
authors.initials: R
authors.lastname: Buzier
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Tusseau-Vuillemin
authors.forename: Célia Martin
authors.initials: CM
authors.lastname: dit Meriadec
authors.forename: Olivier
authors.initials: O
authors.lastname: Rousselot
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Mouchel
mesh_terms: D052918:Environmental Restoration and Remediation; D005602:France; D007220:Industrial Waste; D008670:Metals / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D007220:Industrial Waste; D008670:Metals; D014874:Water Pollutants, Chemical