Construction started on new Georgina drinking water treatment facility

By Ian H. Shrimpton, MacViro Consultants Inc.,
and Ken Dailey, United Utilities Canada Limited

Artist perspective of the 20 ML/day water treatment building.

Construction of the first phase of a new 50 ML/day water treatment plant in Willow Beach, on Ontario's Lake Simcoe, is well under way. Completion of the first phase will see commissioning of a 20 ML/day facility in late 2002. By 2015, it is expected that the plant will expand to its full design capacity of 50 ML/day to accommodate projected growth in the Town of Georgina. When the new plant is commissioned, the Sutton water treatment plant will be decommissioned.

The new treatment facility was initiated in 1996 as part of York Region's "Long-Term Water Strategy". The planning and design process for the Georgina project was conducted according to the provincial Class Environmental Assessment (Class EA) for Municipal Water and Wastewater Projects to provide long-term water supply to meet the needs of Keswick, Sutton, and the intermediate rural lakeshore areas.

Located in the Town of Georgina on the south shore of Lake Simcoe, the facility consists of three main components: a raw water intake, low lift pump station, and water treatment plant. A key element of the treatment plant is a microfiltration membrane. In addition, the treatment plant contains a 3,000 m³ reservoir beneath a high lift pump station within the facility. The high lift pumps transfer water to the existing elevated storage tank in Sutton, and in future will deliver water to a new at-grade storage reservoir in north Keswick.

There were numerous approvals required for the project, including solutions to potential environmental and ecological impacts on the aquatic life of Lake Simcoe. One of the many considerations was the design of the water intake and treatment of the zebra mussel infestation with chlorine.

The location of the intake was established on the basis of available water, depth, quality and physical factors such as waves, currents, boating, zebra mussels and ice that would affect the design of the intake structure and intake pipe, and cost of construction. To meet these design constraints, a steel structure will be installed at a depth of 19 metres, 1.4 kilometres from the shore. Zebra mussels are controlled with a chlorine diffuser that delivers chlorine solution into the intake pipe so that any chlorine residual in the lake is avoided. Near the intake structure, a water sample line is installed to monitor water quality in the lake. A second line terminates within the intake pipe approximately 700 metres from shore so that plant operators can monitor the chlorine dosages being applied.

Lake water flows by gravity to the low lift pump station through a 1,050 mm diameter concrete pressure pipe. The pump station, located on a 0.3 ha site at the north end of Kennedy Road, is designed with two inlet wells, one of which has a screen and associated pumping equipment. The screen blocks large particles from entering the pump wet well areas, and the pumps have a variable frequency drive to match the raw water to the demand of the distribution system. The station is designed to accommodate four identical 16.7 ML/day pumps to provide a 50 ML/day capacity with one pump out of service. The pump station has a below grade concrete wet well which is connected to the intake pipe. The superstructure of the station houses the equipment.

Water is pumped through a 600 mm raw water main directly into the water treatment plant from the low lift pump station. There, the water is pre-treated with an immersed microfiltration membrane technology that eliminates turbidity, and removes suspended solids and protozoan pathogens like Giardia and Cryptosporidium.

The microfiltration system draws water through the membrane surface under a vacuum. Membrane fouling is reduced by air scouring and limiting vacuum levels so that contaminants are not forced into the pores under high pressure. It is expected that the lower differential pressure combined with a reinforced membrane structure will give long membrane life, and reduced membrane replacement costs. The membrane modules are combined to form cassettes and are then immersed directly in the raw water supplied to the process tank.

Other than pre-screening, no further pre-treatment is expected to be required. The membrane system replaces the flocculation tank, clarifier and granular media filters typical of more conventional drinking water treatment systems.

This article was abridged from Environmental Science & Engineering magazine, which also contains many more articles not posted on our Web Site. See our home page on how to order your subscription. We regret we can only accept orders from Canada and the United States.