Mercury loads and fluxes from wastewater: A nationwide survey in Switzerland. (15th May 2020)

• Record Type: Journal Article
• Authors: Suess, Elke; Berg, Michael; Bouchet, Sylvain; Cayo, Lara; Hug, Stephan J.; Kaegi, Ralf; Voegelin, Andreas; Winkel, Lenny H.E.; Tessier, Emmanuel; Amouroux, David; Buser, Andreas M.
• Is Part Of: Water research. Volume 175(2020)
• Publication Date: 2020-05-15
• Subjects: Mercury and methyl mercury -- Discharge -- Wastewater -- Sewage sludge -- Incineration -- Surface water; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.115708
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Mercury (Hg) pollution threatens ecosystems and human health. Wastewater treatment plants (WWTPs) play a key role in limiting Hg discharges from wastewaters to rivers and lakes, but large-scale studies to estimate Hg loads and discharge at national levels are scarce. We assessed the concentration, flux, speciation, and removal of Hg in municipal wastewater throughout Switzerland by investigating 64 WWTPs in a pre-study and a subset of 28 WWTPs in the main study. We also studied the behavior and pathways of Hg along the various treatment steps in a state-of-the-art WWTP. The resulting dataset, representative of industrialized countries, provides an overview of (i) current Hg concentration ranges, (ii) average per capita loads, and (iii) wastewater Hg inputs into surface waters. The results allowed estimation of a total Hg (THg) load in Swiss wastewater of 130 ± 30 kg THg/year (15.7 mg/capita/y), of which 96 ± 4% is retained in sewage sludge. About 4.7 ± 0.5 kg THg/year (0.57 mg/capita/y) is discharged with the treated wastewater into surface waters. This corresponds to only 1.5–3% of the THg load carried by the major Swiss rivers, indicating that >95% of riverine Hg originates from other sources. Extrapolation to the population of Europe would yield a total amount of 11, 700 kg THg/year in raw wastewater, with some 480 kg THg/year discharged to surface waters. Monomethyl mercury on average accounted for 0.23% of THg, and its fraction remained constant along the different treatment steps. Graphical abstract: Image 1 Highlights: Comprehensive baseline study contributing to the goals of the global Minamata Convention. Pathways of Hg studied along wastewater treatment chain and sludge incineration. Quantification of Hg concentration ranges, mass fluxes, and per-capita loads. Average loads were 15.7 and 0.57 mg/person/year in raw and treated wastewater, respectively. Treated wastewaters contribute ≤3% of the total mercury (THg) load of the rivers.