Environmental Science & Engineering - www.esemag.com - June 2004
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Region of Peel building world’s largest low pressure membrane ultrafiltration plant

By Andrew Farr and Scott Lenhardt

The Lakeview expansion (shown under construction at top left) will increase drinking water treatment capacity from 560 ML/day to 820 ML/day. The new facilities, which incorporate ZENON UF membranes with ozonation and BAC technologies, will occupy significantly less space than conventional technologies.

Over the past 30 years few municipalities in Canada have experienced the kind of rapid population and economic growth that the Region of Peel has. With the population increasing threefold during this time, from about 330,000 to over one million residents and still growing, the municipality places a high priority on ensuring that new infrastructure expenditures are long-term investments.

The residential community, while significantly contributing to the growth, is not the only group of people moving into Peel. The business community is also growing each year, making Peel an integral part of the economic engine that drives industry within the Greater Toronto Area, the Golden Horseshoe and South-Western Ontario.

One reason Peel has been successful in attracting new industry is because of its proximity to key Canadian and US markets. Rail, ship, and air transport services are easily accessible and reliable in Peel and municipal infrastructure such as roadway networks, water and sewer services are in place and readily available.

Located on the shores of Lake Ontario, the Region of Peel has direct access to an abundant supply of quality drinking water. Unquestionably, having a secure source of water is one service that is critical for healthy growth and development to occur in any community, as is the ability to finance the delivery of that service.

With this in mind, the Region of Peel began discussions in 2002 to expand its Lakeview Water Treatment Plant (LWTP). Both Regional Council and senior management established key criteria for current and future expansions at the site. It was imperative that the expansion remain within the existing footprint of the plant, produce the highest quality drinking water possible at a reasonable cost, and allow for sufficient capacity to service future needs and opportunities.

After an extensive pilot program, and in consultation with engineering and design firm CH2M HILL, the Region of Peel decided to implement a new, innovative, multi-barrier approach at its LWTP, using ozonation, biologically active carbon (BAC) contactors and hollow-fibre ultrafiltration (UF) membranes.

Upon completion of the expansion, this project will be the largest lowpressure, UF membrane plant in the world with a summer capacity of over 300 ML/d (80 mgd) and a cold water (2°C) capacity of 262 ML/d (69 mgd). Daily water treatment capacity of the plant will rise from the current 560 ML/d (148 mgd) to 820 ML/d (216 mgd).

Products considered for installation at the LWTP needed to demonstrate reliability and longevity. Three leading membrane suppliers were invited to participate in a comprehensive pilot program to test the performance of their products for factors such as solids and pathogen removal. At the conclusion of the study, the ZENON ZeeWeed® 1000 membranes showed the highest quality technical solution at the most reasonable cost.

Drinking water treatment with lowpressure ultrafiltration membranes is becoming increasingly more common throughout North America, and many municipalities have adopted ZENON technology to serve their communities. Reference sites in Collingwood, Ontario (32.5 ML/d, 8.6 mgd); Sudbury, Ontario (37.8 ML/d, 10 mgd) and Racine, Wisconsin (189 ML/d, 50 mgd) were examined closely by Peel staff during the decision-making process.

In determining the best value for Peel, each supplier was also asked to submit a technical proposal which was assigned a relative performance factor. The results from this step were used to adjust each supplier’s cost proposal which considered both capital and 20- year operating costs. Other factors such as service, project delivery, and training also figured prominently in the decision to recommend awarding the $11.8-million membrane purchase.

Ozone and biologically active carbon (BAC) will provide pretreatment for the raw water prior to ultrafiltration. Water from Lake Ontario is moderately hard and usually low in turbidity and organics, but turbidity can rise to high levels for up to a week.

Taste and odour episodes can also occur and are known to last for up to several weeks. Typical turbidity for the lake water can range from less than 1.0 NTU to peaks of greater than 20 NTU. The pretreatment will reduce turbidity and dissolved organic carbon (DOC), and provide taste and odour control.

The Lakeview WTP will incorporate the latest version of ZENON ZeeWeed® membranes and will benefit from the increased flow capacity and reduced space requirements that the new configuration offers.
“The ozone and BAC pretreatment will deliver a consistent quality feed water to the membranes with turbidity below 2.0 NTU, 95 per cent of the time, with total suspended solids below 5.0 mg/L (maximum of 40 mg/L) and DOC ranging from 1.0 - 5.0 mg/L,” said Director of Water and Wastewater Treatment Mark Schiller.

During pilot testing, the pretreatment contributed to more efficient membrane functioning with longer cleaning intervals and trouble-free operation during raw water variability. Overall, the pretreatment will benefit the system with more consistent permeate quality, reduced energy costs, lower chemical consumption, and a reduced risk of membrane damage.

The Lakeview expansion, scheduled for completion in 2006, will add 12 membrane process trains. Each train will consist of a 55 m3 process tank that can hold up to seven ZeeWeed membrane cassettes. Eleven of the trains will operate at all times, with the twelfth train operating on demand whenever one of the others is taken off line for backwashing, scheduled maintenance or testing.

The ZeeWeed ultrafiltration membranes are immersed directly into the membrane tanks and draw water into the fibres using a slight vacuum. The membranes form a physical barrier to particles, preventing suspended solids, turbidity, algae and pathogens such as Giardia and Cryptosporidium from passing into the permeate.

Operation of this system will be highly automated and fibres can be easily cleaned with a clean-in-place backpulsing process that forces nonchlorinated permeate water back through the membranes. This dislodges any particles that may adhere to the membranes. Intermittent aeration of the membranes is also used to scour debris from the fibres, and when necessary, membrane cassettes can be removed from service, and placed in a separate cleaning tank to dissolve solids from the fibres. With regular maintenance and inspections, each membrane cassette will provide years of efficient and cost-effective operation.
Andrew Farr, P. Eng., is Manager, Capital Works, for the Regional Municipality of Peel,
contact e-mail: farra@peelregion.ca.
Scott Lenhardt, P. Eng. is Regional Manager with ZENON Environmental Inc.
contact e-mail: slenhard@zenon.com.

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