Expansion At Lakeview

The Lakeview Water Treatment Plant in Mississauga, Ontario is currently the world’s largest plant that combines ozone, biologically activated carbon, and ultrafiltration membrane processes.

The Region of Peel, which provides drinking water to over one million people, owns the Lakeview Water Treatment Plant on the shores of Lake Ontario in Mississauga, west of Toronto.

With the recent commissioning of its $145-million Phase 1 expansion, plant production increased from 560 to 820 million litres per day (ML/d), making it the world’s largest drinking water plant with ozone, biologically active carbon (BAC) and membrane ultrafiltration.

Upon completion of Phase 2 ($200-million), the Lakeview WTP will have a total plant capacity of 1,150 ML/d. Phase 1 was commissioned in June 2007; Phase 2 was awarded to CH2M HILL later that month, and preparations for an environmental assessment are under way.

High water quality and sustainability goals

As with many other utilities in large urban centres, Peel Region faces the challenge of providing safe and aesthetically pleasant drinking water to a fast growing population. The region has an aging infrastructure, but in order to expand its water treatment facilities it must balance financial,

spatial and time constraints. It also has to meet more stringent regulatory requirements.

For its new plant expansion, Peel wanted to achieve the best water quality, while optimizing the use of automated control and staff operations and maintenance. Sustainability goals for the plant were increased energy efficiency and a reduced use of chemicals. The production of residuals from the water treatment process was also to be minimized.

While some environmental goals can be developed under the Leadership in Energy and Environmental Design (LEED) certification, the key contributor to a more environmentally sustainable water treatment facility is the treatment process.

Selecting the process train

The source water for the Lakeview water treatment plant is Lake Ontario. The water is characterized by low levels of natural organic matter and disinfection byproduct precursors, low turbidity, and stable water quality with seasonal water quality excursions (taste and odour, turbidity).

In 2003, CH2M HILL and Peel Region identified objectives for the treatment process that exceeded provincial regulations. An exhaustive selection process was then done, comparing over 20 treatment alternatives. These included assessing a variety of conventional (clarification and filtration) and advanced treatment (membrane filtration, ozone, ultraviolet disinfection, advanced oxidation) technologies.

At the end of the selection process, a combination of ozone, biologically active carbon(BAC), and membrane filtration was deemed to offer the best value (water quality, performance, environmental footprint, social benefits, and cost efficiency). The treatment train provides multiple barriers for disinfection, taste and odour control, and turbidity removal without the use of coagulation chemicals. The treatment of emerging trace contaminants such as endocrine disruptors and personal care products is provided as well.

A six month pilot study was then carried out with two process sequences: (a) ozone, BAC, and membrane ultrafiltration; and (b) membrane ultrafiltration, ozone and BAC. Cost, performance and design criteria were developed for both sequences. The pilot data showed that the cost savings of the process in which the enhanced membrane ultrafiltration flux followed BAC more than compensated for the slightly higher ozone dose necessary to achieve the desired inactivation and removal of Cryptosporidium and taste and odour from the raw water.

The process of ozone, BAC and membrane ultrafiltration followed by chlorine disinfection and fluoridation was therefore selected. A process schematic of the 560 ML/d conventional treatment (circa 1950) and the parallel 360 ML/d OBM treatment WTP (circa 2007) is shown in the diagram.

Two ozone generators provide ozone to the treatment process, after which the water is passed through the BAC facility. The next process is configured with an operating installation of 7,560 ultrafiltration modules housed in a large membrane gallery, one of the largest such installations in the world.

“We were extremely pleased with the results of the pilot testing,” said Mark Schiller, Peel’s Director of Water Division. “Not only were we able to gather the data we needed to optimize the treatment process, but the performance of the pilot proved that a large-scale plant, using ozone, BAC, and membranes, can handle any potential upset situation and will consistently deliver high-quality drinking water no matter what the conditions might be in the lake.”

Leaving land for the community

The Lakeview WTP project site is surrounded by residen- tial, industrial and recreational areas. Peel Region and CH2M HILL worked closely with community stakeholders during the public consultation phase to minimize the social and environmental impact of the facility during construction, start-up and operation.

A comparison of the land footprint of the conventional and OBM treatment processes was an important factor. The OBM process provides 40% more treatment capacity in half the footprint compared to the conventional treatment process. The compactness of the OBM process not only maximized the use of space within the facility, space which is required for a future expansion, but also allowed for the preservation of land that had historically been used for recreational purposes by the community, such as a baseball diamond. Once construction on site is completed, the baseball diamond will be returned to the community.

In addition, construction areas were limited to the east side of the site where a nearby school and marina would receive the least impact of noise, dust and traffic.

The Phase 1 expansion project was one of the featured tours of the American Water Works Association Annual Conference held in Toronto in June 2007. Over 200 visitors from as far away as Australia and South Africa toured the plant.

Client: Region of Peel

Prime Consultant: CH2M HILL, Toronto (Peter Mallory, P. Eng.,John Mills, P. Eng., Ken Mains, P. Eng., Laurie Boyce)

Geotechnical consultant: GeoCanada

Contractor: NAC North America Construction