By Don Nash, P.Eng., Urban Systems
Reclaiming Wastewater in Dawson CreekEnvironmental Water & Wastewater Environment Wastewater treatment systems
The idea for a Reclaimed Water Facility in the City of Dawson Creek in northeastern B.C. began with the realization that water scarcity is a global issue that must be solved locally through collaboration between industry and the...
The idea for a Reclaimed Water Facility in the City of Dawson Creek in northeastern B.C. began with the realization that water scarcity is a global issue that must be solved locally through collaboration between industry and the public. Extreme drought conditions were limiting the city’s ability to supply truck filling stations with enough potable water to support the region’s hydraulic fracturing operators. Hydraulic fracturing (“fracking”) involves injecting a fluid (usually water with additives) into a well bore under high pressure. The process unlocks shale gas that is trapped in very small pores of fine-grained sedimentary rock.
The solution to the water shortage arose from a simple question: why is sewage considered a waste rather than a resource that can be used for hydraulic fracturing in a manner that is beneficial for society, the economy and the environment? To test this idea, the city hired Urban Systems to conduct a feasibility study.
After the preliminary feasibility study, and after identifying potential treatment technologies and holding extensive consultation with the natural gas industry, a detailed request for proposals was issued. The approach was found to be so compelling that four companies submitted proposals. Ultimately the city partnered with Shell Canada on the project.
Wastewater treated and piped to Shell natural gas field
The project draws wastewater from the city’s existing aerated lagoon wastewater treatment system. It then further treats the water using a trademarked technology known as submerged attached growth reactors (SAGR) built adjacent to the lagoon system. Effluent from the SAGR system is further polished using coagulation and disc filtration equipment housed within a new building on the project site. The treated water is disinfected and stored in a wet well below the new building.
The reclaimed water is then piped 48 kilometres to the west to Shell’s Groundbirch venture, which has five natural gas processing plants, over 250 wells and a gas collection system. The operation is currently producing enough natural gas to meet the needs of approximately 400,000 Canadian homes. Piping the reclaimed water to Groundbirch rather than trucking it reduced traffic, noise and dust, which are among the top concerns of local landowners. The pipeline option is expected to eliminate 3 million kilometres a year in truck trips over the full course of full gas field development.
The project involved constructing the LEED-certified treatment facility, a new municipal reclaimed water truck filling station, a Shell Canada owned and operated pump station, and the pipeline to transport the water to Shell’s field operations.
Designed to treat 4,000 cubic meters per day (m3/d), the project has significant economic benefits. The city received the majority of funding from Shell Canada to support the design and construction, in return for Shell securing access to the reclaimed water for 10 years. Shell Canada is allocated 3,400 m3/d, and 600 m3/d is allocated to the city’s bulk truck filling station. The city can sell the water to local industry, potentially earning $5.5 million over the 10 years. If there is surplus water over the 4,000 m3/d the city can sell that as well.
Treatment using SAGR cells
The SAGR is a clean gravel bed with a horizontal chamber at the front end of the system to distribute secondary wastewater flow across the width of the cell, and a horizontal collection chamber at the back end of the system. Each cell is essentially a large aerated trickling filter that uses clean gravel as the media for the organisms that digest the waste (biomass), to grow on. Each cell is constructed below grade and covered in mulch to help insulate the process to improve the operation during the winter months. The biomass will naturally grow and attach to the gravel bed and use the waste in the water as food.
Although the water is highly treated upon leaving the SAGR cells, it is further polished by coagulation and disc filtration to meet the water quality requirements. The water is chlorinated for disinfection prior to distribution for oil and gas activities. British Columbia currently has four categories or levels of treatment for reclaimed water. The water produced at the facility meets the quality requirements for three of those categories, providing a wide range of reuse opportunities.
Special consideration had to be given to the uses of the reclaimed water, and to how it would be handled in the field and in the event of a spill. Also, given that reclaiming the water reduced the discharge to Dawson Creek, careful consideration was given to the potential impacts on fish habitat. The creek was monitored during the commissioning period.
The treatment system has proven itself in the northern environment and has opened the door for other northern facilities to use this technology in an entirely new range of applications.
Ultimately the project was about partnering with industry to help finance a reclaimed water facility to reduce the demand for potable water for non-potable uses.
Urban Systems is now working with a number of local governments on reclaimed water opportunities. cce
Owners: City of Dawson Creek/
Prime consultant: Urban Systems
(Don Nash, P.Eng., Peter Coxon, P.Eng.)
Project management: MHPM
Technical reviews: NovaTech,
SAGR system design/supply:
Other key players: Toyo (Shell pump station and pipeline design); Stantec (commissioning); Public Design & Communications (architecture); CWMM (structural), ICI (electrical/instrumentation); HPF (heating/ventilation); Enersys(model); Maple Reinders (construction main process facility); Tritech (construction SAGR cells)
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