Lions Gate Secondary Wastewater Treatment Plant, Vancouver, Canada
The Lions Gate Secondary Wastewater Treatment Plant (WWTP), which is expected to come online in December 2020, will replace the existing Lions Gate Primary WWTP. The new project is located approximately 2km east of the existing WWTP and Lions Gate Bridge in North Shore, Vancouver. The site, covering an area of approximately 3.5ha, is located on a former British Columbia Railway land.
In November 2013, the indicative design for the new WWTP was approved by the Metro Vancouver Board.
The detailed engineering and architectural design phase will commence in 2014, while construction is scheduled to start in 2017. The new plant will be designed with an option to be expanded to include tertiary treatment in future.
Funding for Lions Gate Secondary WWTP
The project will be implemented through the design-build-finance (extended warranty) procurement approach, under which Metro Vancouver will maintain and operate the new plant. The budget for the current project is estimated at $700m.
Financing for the project will be partially provided through the Building Canada Fund, which is providing $14bn over ten years for major economic projects, including a $10bn allocation to a Provincial-Territorial fund for infrastructure projects, such as wastewater treatment.
Need for the secondary plant
The Missouri River (WWTP) is located south of the Veterans Memorial Bridge in Omaha City.
The existing Lions Gate WWTP, which was opened in 1961, is one of the two remaining primary WWTPs in Vancouver. The second primary treatment plant, Iona Island WWTP, is expected to be upgraded by 2030.
All primary treatment plants in Canada are required to be upgraded to secondary treatment as per Metro Vancouver's Integrated Liquid Waste and Resource Management Plan, approved by the BC Ministry of Environment in May 2011. The new secondary treatment plant will meet the environmental requirements set by the Canadian Council of Ministers of the Environment (CCME).
Special design features of the WWTP
Indicative designs for the Lions Gate Secondary WWTP integrate a fully enclosed two-stage odour control system and a permanent air quality monitoring station to be constructed within or near the site. A vegetated buffer along the north side of the plant will be created and the spaces featuring mechanical equipment will be acoustically insulated to minimise noise.
The new WWTP will integrate the surrounding community, with its main building to be located along 1st Street West to reduce the visual impact of the building and optimise the limited available space. An outdoor public space will be created at the foot of Pemberton Avenue and space for community use will be provided within the building for education, outreach and public meetings.
Sustainability and energy efficiency features
Sustainability features of the new WWTP include rain harvesting and green roof systems. The plant will be designed for a life span of 80 years, with all the major equipment to be installed at a safe height to protect them from a 100-year sea level rise.
Biogas produced by the treatment process will be recovered to generate electricity at the site, heat from the treated effluent will be supplied to a local district energy system and biosolids from the plant will be conveyed to the neighbouring areas for land reclamation and soil fertilisation.
Secondary treatment process at Lions Gate
The new WWTP will implement a six-stage treatment process for treating wastewater, involving influent pumping, preliminary treatment, primary treatment, secondary treatment, high-rate clarification and disinfection.
Wastewater will be conveyed via trunk sewers to the influent pump station, which will pump the wastewater directly to the preliminary treatment process where materials including plastics, rags, grit and fats, oils and grease (FOG) will be removed.
The wastewater will then go through a primary treatment process where the suspended solids will be settled through gravity in the lamella settlers.
The secondary treatment process will integrate deep tank activated sludge and stacked secondary clarifiers, to enable bacteria and other microorganisms (activated sludge) in the tanks to grow and break down organic matter to produce carbon dioxide and water.
Wet weather flows will be treated using a high-rate clarification process, wherein the effluent from the high-rate clarification process will be blended with secondary effluent and flow to the disinfection process, where they will be disinfected implementing UV light and sodium hypochlorite.
Disinfected water will finally be conveyed to the existing outfall and discharged to the Burrard Inlet. The flow of wastewater throughout the plant and to the outfall will be enabled by gravity, without requiring additional pumping.
Solids treatment at Lions Gate Secondary WWTP
Treatment of solids at the site will include mechanical thickening, which involves removal of water from the primary and secondary sludge streams. The sludge will then be blended, pre-heated and pumped to the digestion process.
The digestion process will make use of thermophilic anaerobic digestion to stabilise FOG, including the primary and secondary sludge streams in the digester tanks. The process will further produce biogas to generate electricity and heat.
Biosolids from the digestion process will finally be pumped to a dewatering process to remove excess water, which will reduce the volume of the final product before being conveyed for agricultural and land reclamation purposes.