title: Local environmental conditions determine the footprint of municipal effluent in coastal waters: a case study in the Strait of Georgia, British Columbia.
abstract: To predict the likely effects of management action on any point source discharge into the coastal ocean, it is essential to understand both the composition of the effluent and the environmental conditions in the receiving waters. We illustrate a broadly-applicable approach to evaluating the comprehensive environmental footprint of a discharge, using regional geochemical budgets and nearfield monitoring. We take as a case study municipal effluent discharged into the Strait of Georgia (west coast of Canada), where there has been public controversy over the discharge of screened or primary-treated effluent directly into the ocean. Wastewater contributes ≤ 1% of the nitrogen, organic carbon and oxygen demand in the Strait and is unlikely to cause eutrophication, harmful algal blooms or hypoxia in this region. Metals (Hg, Pb, Cd) are controlled by natural cycles augmented by past mining and urbanization, with 0.3-5% of the flux contributed by wastewater. Wastewater contributes ~5% of PCBs but ≤ 60% of PBDEs and is likely also important for pharmaceuticals and personal care products. Effects of high organic flux on benthos are measurable in the immediate receiving environment. The availability of particle-active contaminants to enter the food chain depends on how long those contaminants remain in the sediment surface mixed layer before burial. Secondary treatment, slated for completion in Vancouver in 2030, will reduce fluxes of some contaminants, but will have negligible effect on regional budgets for organic carbon, nitrogen, oxygen, metals and PCBs. Removal of PBDEs from wastewater will affect regional budgets, depending on how the sludge is sequestered.
authors.affiliation: Institute of Ocean Sciences, Fisheries and Oceans Canada, 9860 W. Saanich Rd., P.O. Box 6000, Sidney, BC V8L 4B2, Canada. Electronic address: sophia.johannessen@dfo-mpo.gc.ca.
authors.forename: Sophia C
authors.initials: SC
authors.lastname: Johannessen
authors.affiliation: Institute of Ocean Sciences, Fisheries and Oceans Canada, 9860 W. Saanich Rd., P.O. Box 6000, Sidney, BC V8L 4B2, Canada. Electronic address: robie.macdonald@dfo-mpo.gc.ca.
authors.forename: Robie W
authors.initials: RW
authors.lastname: Macdonald
authors.affiliation: Ecostat Research Ltd., 1040 Clayton Rd., N. Saanich, BC V8L 5P6, Canada. Electronic address: bburd@telus.net.
authors.forename: Brenda
authors.initials: B
authors.lastname: Burd
authors.affiliation: Metro Vancouver, 4330 Kingsway, Burnaby, BC V5H 4G8, Canada. Electronic address: avanrood@telus.net.
authors.forename: Albert
authors.initials: A
authors.lastname: van Roodselaar
authors.affiliation: Metro Vancouver, 4330 Kingsway, Burnaby, BC V5H 4G8, Canada. Electronic address: bertold@shaw.ca.
authors.forename: Stan
authors.initials: S
authors.lastname: Bertold
mesh_terms: D001955:British Columbia; D004777:Environment; D004784:Environmental Monitoring; D005068:Eutrophication; D019015:Geologic Sediments / Q000737:chemistry; D055768:Halogenated Diphenyl Ethers / Q000032:analysis; D008670:Metals / Q000032:analysis; D008906:Mining; D009584:Nitrogen / Q000032:analysis; D011078:Polychlorinated Biphenyls / Q000032:analysis; D014865:Waste Disposal, Fluid / Q000706:statistics & numerical data*; D062065:Wastewater / Q000737:chemistry / Q000706:statistics & numerical data*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D055768:Halogenated Diphenyl Ethers; D008670:Metals; D009584:Nitrogen; D011078:Polychlorinated Biphenyls; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Contaminants; Geochemical budgets; Municipal effluent; Nitrogen; Organic carbon; Oxygen