Saskatoon Wastewater Treatment Plant, Saskatchewan, Canada

The Saskatchewan City of Saskatoon is four years into a ten-year expansion programme intended to prolong the useful life of its wastewater treatment plant (WTP) by a quarter century. Water and wastewater projects are set to account for some C$44m of the city’s proposed 2008 capital budget.

The bulk of the 2008 funding is going towards a new UV disinfection system and filter plant expansion at the city's facility. The remainder is to be spent on plans designed at reducing sewer backups, improving wastewater collection and mitigating flooding, along with a series of maintenance projects.

The UV system is budgeted at C$13m, with the filter plant upgrade and expansion expected to cost up to C$17m. The overall WTP improvement project has an estimated total cost of C$130m.

In addition, the proposed 2008 capital budget allocates C$2.3m for wastewater collection and a further C$2m to alleviate basement flooding.

Expanding the WTP will allow it to meet higher water quality standards and increase average production by almost 100,000m³ per day. New initiatives on wastewater resulted from heavy flooding in the spring and summer of 2007.

BACKGROUND

Saskatoon formally became a city in May 1906, with a population of 5,000. The city currently has nearly a quarter of a million inhabitants. Located beside the South Saskatchewan River, Saskatoon covers 144km² and includes a large area of parkland along the river.

The WTP was first built in 1906, using steam-driven pumps to draw water into a clay-lined sedimentation basin. In 1910, a rapid sand filtration plant – which remains in service to this day – and electrically-powered centrifugal pumps were installed.

Since these first upgrades, the plant has undergone a series of expansions to meet growing demand with capacity trebling in the last fifty years. The current programme of works is intended to address further growth and changes in regulatory requirements.

WATER TREATMENT

The South Saskatchewan River provides the WTP with its source water. The flow is initially screened before being pumped to the plant where it enters sand filtration and is subsequently dosed with potassium permanganate and ferric sulphate.

Lime is added to reduce turbidity in the clarifiers and radial launders draw off the clear water from the top. Excess floc sludge is back-flushed to the river. The treated water is then dosed with chlorine and fluorine before flowing to the sedimentation tank for filtration.

The WTP currently uses both rapid sand and sand/anthracite filters; the planned work at the filter plant includes upgrading the existing sand beds to dual media.

The new UV disinfection system is necessary to meet lower chlorine standards put in place by provincial and federal authorities. The existing chlorination system must be replaced by 2009 to comply with the Canadian Environmental Protection Act.

After around 30 mins in clearwell storage, the water flows into the city’s distribution system. Process control includes full system alarm, data logging and reporting functions – installed during an earlier improvement scheme in the 1990s – and automatic chemical dosing.

WTP EXPANSION

The ten-year WTP expansion project began in 2004, with the construction of a new sludge handling facility and the relocation of the plant’s electrical towers. This was followed by the completion of a new operations facility, the commencement of a phased upgrade of the chlorination system and the purchase of land designated to host the new maintenance building (with construction beginning the following year).

The sludge handling facility was completed in 2006 along with a new pump-house and water intake. Reservoir capacity was expanded during 2007 to improve treated water storage.

In addition to the new UV disinfection system and the expansion of the filter plant, increased pumping capacity will be installed during 2008 at the 42nd Street Reservoir to give greater process control and better circulation of water within the reservoir.

A new water intake is also scheduled for 2008 - at a cost of C$33m - funded by an earlier round of expenditure.

When the project reaches its scheduled completion in 2014, the useful life of the WTP will have been extended by 25 years.

KEY PLAYERS

Saskatoon City Utility Department is responsible for the ownership and operation of the plant and infrastructure. The WTP supplies water to users beyond Saskatoon’s boundaries under a Master Water Supply Agreement to Sask Water Corporation.

Health Canada is the official body responsible for regulating water quality; Saskatchewan Environment is the permitting authority. Upgrades to the process control systems were made by Sceptre; Phase 1 improved automation and design and construction services are being provided by Associated Engineering.