Gold Bar operations

Pre-treatment protects plant equipment by removing large pieces or materials that would otherwise create wear and tear on the plant while also improving quality of organic solids (which play an important part in later treatment).

• Wastewater enters long narrow tanks called “grit chambers” designed to slow down the flow so solids can settle out of the water
• Heavier material called grit (sand-like particles mixed with debris and mud) drops to the bottom of the tank and is removed
• Flow exits grit tanks through screens, which trap and remove materials like plastic, rags and wood
• Screenings and grit are hauled to a local landfill

1a. Primary treatment

Primary treatment consists of gravity-settling aided by a rake mechanism.

• Heavier particles (solids) sink to the bottom and lighter particles (scum) float to the top
• A rake moves the different particles to a collection point
• The rake then also rises to the surface to remove the floating “scum”

​1b. Enhanced primary treatment (stormwater)

During wet weather periods the combined sewers often capture more runoff than they can handle, resulting in wastewater overflow to the river.

• Enhanced primary treatment allows the plant to take in and treat more seasonal flows, reducing the amount of untreated overflow entering the river

Solids go to the fermenters and digesters for treatment to create “biosolids” which can be re-used as fertilizer.

2. Secondary treatment

Microorganisms digest nitrogen and phosphorus in the water and then settle out in the clarifiers to clean the water further.

• By the end of this stage, 95-97% of organic impurities have been removed

3. Tertiary treatment

Cleaning the water further (polish & disinfect)

3a. Membrane filtration

A small portion of treated wastewater is diverted for membrane filtration.

• Membrane filters are a series of porous synthetic strands containing millions of microscopic pore openings that allow water to pass but act as a barrier to even the smallest bacteria

3b. UV disinfection

Before being returned to the North Saskatchewan River after almost 18 hours of treatment, the clear wastewater effluent is disinfected by high intensity ultra-violet light.

• After a few short minutes, this chemical-free process renders the treated wastewater safe for contact through different recreational activities through the outfall

Each day an average of 265 million litres flow through the Edmonton WWTP with the full tertiary treatment process taking 17-18 hours from start to finish, but the plant's current design can treat up to 310 million litres per day. Some other capacity figures include:

Record breaking capacity levels
The highest peak daily flow occured on July 15, 2012 at 1,170 million litres. And the highest annual flow was in 2013 at 103,761 million litres. Yearly fluctuations are due to effects of annual precipitation entering the combined sewer system (~15% of city’s area).

• Peak primary treatment capacity: 910 million litres/day
• Peak secondary/tertiary treatment capacity: 420 million litres/day
• Headworks (grit removal and screening) capacity: 1,200 million litres/day
• Combined digester (8 anaerobic digesters that treat sludge) capacity: 67.5 million litres/day
• Biogas produced (average per year): 11 million m³

Gold Bar also provides biosolids to farmers and has distributed close to 550,000 dry tonnes of biosolids to over 16,000 hectares of farmland since 1978. The biosolids program is available to Edmonton-area farmers. Additionally, more than 180,000 dry tonnes of biosolids have been made into compost products for sale since 2000.

Since its beginnings, Gold Bar has undergone two major processing capacity (primary and secondary treatment) increases; they occurred a decade apart, with the last in 1981. Solids handling capacity increases occurred right up to 2011, with the addition of 2 new digesters. The plant site has room on the eastern perimeter, if needed and if the same configuration is followed, for three more bioreactors/clarifiers or up to 126 million litres per day. See how we're planning for future flows at Gold Bar.

Treatment upgraded

Improved effluent quality: tertiary treatment upgrade began in 1995 and was completed in December 2001, three years ahead of the mandated deadline from the province.

Biological Nutrient Removal (BNR) upgrade

Facilities to support the BNR upgrade component include primary sludge fermenters; sludge blend tanks; Waste Activate Sludge (WAS) thickeners; two new bioreactors/clarifiers; and a new 3,500 horse power blower.