West End Water Pollution Control Centre (WEWPCC) project upgrades
The WEWPCC has three stages of wastewater treatment:
- Primary treatment
- Secondary treatment
- Polishing ponds that accept the secondary effluent and provide additional seasonal disinfection and additional seasonal nutrient removal1
Two major expansions are planned for the WEWPCC. The first expansion will be the addition of biological nutrient removal to the existing secondary treatment process. This will significantly reduce effluent nitrogen and phosphorus loads to the Assiniboine River and ultimately to Lake Winnipeg. The other expansion will be the addition of a year-round ultraviolet effluent disinfection facility. Ultraviolet disinfection will reduce the concentration of pathogens (bacteria) in the final effluent to the limits required by the plant licence2. The WEWPCC biological nutrient removal and ultraviolet disinfection are expected to be completed in 2006 at an overall cost of approximately $30.63 million.
These two projects will require changes in the operation and set-up of the plant. The highlights of those changes are:
- Primary clarifiers
The most significant change will be how the primary clarifiers handle solids. Raw sewage will continue to flow into the two primary clarifiers but waste activated sludge (biological material in excess of what can be recycled into raw sewage) will flow to a new dissolved air floatation system.
- Ferric chloride dosing room
Ferric chloride is a chemical that is added to reduce gas and odour and to help remove total suspended solids and phosphorus. A new ferric chloride dosing room will be located close to the headworks building. The headworks building is where the untreated sewage enters the plant to undergo screening and grit removal. This new facility will provide odour control for the headworks building, primary clarifiers and sludge storage tanks. The new ferric chloride dosing unit will be equipped with a new storage tank that will hold enough ferric chloride for approximately 35 days. Ferric chloride will be used to remove phosphorus when a bioreactor is out of service for maintenance or when phosphorus concentrations exceed the discharge licence limit.
- Primary sludge fermenters
A new primary sludge fermentation system will provide optimal conditions for biological removal of excess phosphorus.
- Waste activated sludge thickeners
A new waste activated sludge thickening system will be added to provide treatment for excess secondary sludge diverted from the bioreactors.
- Secondary clarifier
An additional secondary clarifier (for a total of three at this plant) will be built south of the existing clarifiers. The new clarifier will be similar in size to the existing circular clarifiers at about 30m in diameter.
- Polymer feed for chemically enhanced phosphorus treatment
A dry polymer system will be added as a standby system to achieve a higher solids capture rate and to improve the dissolved air floatation operation during periods when one dissolved air floatation unit is temporarily out of service for maintenance.
- Bioreactors and aeration system
The two existing aeration tanks at the plant will be partitioned into eight different zones to provide efficient flow of oxygen to the bioreactors.
- Ultraviolet disinfection
The new ultraviolet disinfection facility will be located on the south side of Wilkes Avenue to treat effluent from both the polishing ponds and the secondary clarifiers. A new gravel road will be built to provide access to the ultraviolet disinfection facility from Wilkes Avenue. The electrical power requirements for the ultraviolet disinfection system will come from the plant's existing hydro service. The new ultraviolet system will be equipped with 132 ultraviolet disinfection lamps. These lamps will be the same technology used at the South End Water Pollution Control Centre ultraviolet disinfection facility. A new building, approximately 7.6m wide by 26.6m long will be constructed to house the new ultraviolet disinfection facility at the WEWPCC.
The construction work will be limited to the existing site, which is located about 1 km south of the Assiniboine River. No work will be done on the polishing ponds or the outfall near the river.
These components of the project are linked to other components of the overall wastewater treatment program:
- WEWPCC sludge is hauled to the NEWPCC for final processing. WEWPCC nutrient control may create additional biosolids, which could affect the NEWPCC solids control program as well as the biosolids program.
- The combined sewer overflow control plan. There are several small combined sewer districts within the WEWPCC service area.
1 The polishing ponds provide cooling in the winter to prevent open ice on the Assiniboine River. Ducks Unlimited has also asked that the City keep the polishing ponds for habitat reasons.
2 Ultraviolet disinfection may not be required if it can be demonstrated that the existing ponds can meet final effluent bacteria requirements.
3 Cost estimates are from the 2006 Water and Sewer Utility Rates Report, November 8, 2005. Costs will be adjusted for inflation and additional project scope.