Sewage in the Strait of Georgia: how big is the problem and what can we achieve by treatment?
Presentation Abstract
The discharge of municipal wastewater from Vancouver and Victoria into the coastal ocean is controversial. The controversy stems in part from a lack of a common understanding of the scope of the problem and of what might be achieved by further treatment. We have determined the footprint of wastewater in the Strait of Georgia, using regional geochemical budgets and nearfield monitoring. We present the results of this work together with an analysis of the likely effects of secondary treatment. Wastewater contributes less than 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 about 5-10% of PCBs but as much as 60% of PBDEs and is likely also important for pharmaceuticals and personal care products. The high organic flux affects benthic animals in the sediment immediately around the studied outfalls (Iona and Macaulay). Secondary treatment, slated for completion in Vancouver and Victoria over the next 15 years, 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. Sludge disposal on land might result in increased cycling of PBDEs in streams and groundwater.
Session Title
Contaminants of Emerging Concern: Intersection of Occurrence, Impacts, Research, and Policy
Conference Track
Fate and Effects of Pollutants
Conference Name
Salish Sea Ecosystem Conference (2016 : Vancouver, B.C.)
Document Type
Event
Start Date
2016 12:00 AM
End Date
2016 12:00 AM
Location
2016SSEC
Type of Presentation
Oral
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Sewage--Georgia, Strait of (B.C. and Wash.)--Analysis
Geographic Coverage
Salish Sea (B.C. and Wash.); Georgia, Strait of (B.C. and Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Sewage in the Strait of Georgia: how big is the problem and what can we achieve by treatment?
2016SSEC
The discharge of municipal wastewater from Vancouver and Victoria into the coastal ocean is controversial. The controversy stems in part from a lack of a common understanding of the scope of the problem and of what might be achieved by further treatment. We have determined the footprint of wastewater in the Strait of Georgia, using regional geochemical budgets and nearfield monitoring. We present the results of this work together with an analysis of the likely effects of secondary treatment. Wastewater contributes less than 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 about 5-10% of PCBs but as much as 60% of PBDEs and is likely also important for pharmaceuticals and personal care products. The high organic flux affects benthic animals in the sediment immediately around the studied outfalls (Iona and Macaulay). Secondary treatment, slated for completion in Vancouver and Victoria over the next 15 years, 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. Sludge disposal on land might result in increased cycling of PBDEs in streams and groundwater.
