EPCOR with Associated Engineering recognized for environmental commitment

Ron Kruhlak of McLennan Ross (R) presents 2008 Emerald Award to Ian Wright of Associated Engineering (L) and Rob Towstego of EPCOR (Middle)

The Alberta Emerald Foundation presented EPCOR and Associated Engineering with the 2008 Emerald Award for Large Business for the E.L. Smith Water Treatment Plant Upgrade. Presented on June 3 in Edmonton, the Emerald Award recognizes businesses, individuals, non-profit organizations, communities, and government institutions which demonstrate commitment to preserving and enhancing Alberta’s environment.

The E.L. Smith Water Treatment Plant is one of two plants in Edmonton owned and operated by EPCOR that provide treated water to over one million people in the City of Edmonton and surrounding communities. With continued population and economic growth in the area, EPCOR needed to increase the plant’s production capacity from 240 million litres per day to 400 million litres per day, with the infra- structure available to ultimately increase capacity to 600 million litres per day. EPCOR retained Associated Engineering to design the plant upgrade.

The major components of the plant upgrade included a new river water intake, new raw water pump house and transmission main, hydraulic improvements, treatment process upgrades to the clarification, filtration, and chemical feed systems, new water disinfection systems, site upgrades, and a new potable water transmission main with a river crossing below the North Saskatchewan River bed. As part of the upgrades, EPCOR also wanted to improve plant reliability, flexibility, robustness, and ease of operation and maintenance.

The plant upgrade incorporated a number of significant innovations that minimized impacts on the environment.

Environmentally Friendly Disinfection Process
The plant previously used chlorine gas for water disinfection, which is a common standard in the water treatment industry. This practice required storing 1000 kilogram gas containers on site. The plant capacity upgrade would have resulted in significantly more gas chlorine deliveries and increased gas chlorine storage requirements. While EPCOR had systems in place to manage potential risks of its chlorine system, they were concerned that expanding the chlorine gas system could increase potential risks to the environment as well as operator and public safety.

After considering a number of alternative disinfection approaches, EPCOR decided to replace the chlorine gas system with an on-site sodium hypochlorite generation system. This system uses salt as the disinfection chemical, which is safer for plant operators to handle. The system generates a weak (0.8%) sodium hypochlorite solution from the salt, thus eliminating the potential hazards associated with transporting, handling, and delivering large chlorine gas containers, lowering risk and liability, and increasing public safety. The E.L. Smith on-site sodium hypochlorite generation system is the largest system of its kind operating in a major water treatment plant in Canada.

Unique River Water Intake with Fish Return System
The 1000 million litre per day raw water intake is a low profile, bed-style, prism-shaped structure located on the river bed approximately 3 metres below the surface of the water. The structure has entry ports with louvered screens that deflect most fish from entering intake lines leading to the pump house. In addition, the intake has a very low suction velocity (0.01 metres per second) so most fish can easily swim away from the intake. The new intake system includes four 155 metre long by 1.5 metre diameter raw water pipes which connect the raw water intake structure to a new raw water pump house. For any fish that get into the raw water pump house, a unique, mechanical, fish-return system gently returns these fish back to the river. Computer and physical model- ing were used to design the river intake and the pump house screening system to ensure that at least a 95 percent fish survival rate would be achieved. The raw water intake and fish return system thus better preserves aquatic life in the North Saskatchewan River compared to the original intake.

Reuse of Existing Infrastructure
The E.L. Smith water treatment plant has two turbidity removal clarifiers each with a capacity of about 200 million litres per day. However, the piping between the clarifiers and the filters limited the total plant production to approximately 240 million litres per day. The design team developed a number of modifications to the piping to increase the hydraulic capacity to 600 million litres per day, and provide greater process flexibility and reliability. In addition, a former water softening unit was retrofitted to function as a turbidity removal clarifier, thus further increasing system reliability and flexibility.

The design team also developed a concept to reuse the space no longer required for storing chlorine gas tanks for the additional chem- ical storage and feed systems required. Thus, no increase to the plant footprint was required for these systems. The 150% potential increase in production capacity was achieved with only a 20% increase in plant footprint. By reusing existing infrastructure, we reduced the need for demolition and disposal of materials and use of new materials, and minimized building power, heating, and gas requirements.

Plant Operations Maintained During Construction
The design and construction of upgrades to the E.L. Smith Water Treatment Plant are substantially complete and EPCOR officially opened the upgraded plant on June 20, 2008. Project Manager, Hans Wolf reports, “Construction was completed while maintaining operation of the plant and without compromising quality of the treated water, a significant achievement considering the reuse of existing infrastructure to increase plant capacity.“