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Water-energy nexus: finding hidden energy savings in existing municipal infrastructure

Balancing advanced water treatment with energy efficiency is possible

By Nicole McLellan, Waterloo ON

There’s a good chance the cost of your tap water is going up due to climate challenges and pesky emerging contaminants, so we’re on the hunt for energy savings in existing water treatment plants to reduce the carbon footprint and energy costs of municipal operations. The primary objective of water treatment is to produce safe water, but often the co-benefits of energy efficiency can be neglected during design and operation. Energy costs are growing rapidly for municipal drinking water providers. In some cases, energy now accounts for up to 50% of operational budgets.

To explore potential energy savings, we recently worked with the Region of Waterloo’s Middleton Water Supply System - the Region’s largest groundwater treatment plant. We designed and conducted a comprehensive full-scale sampling and assessment program of advanced oxidation process (AOP) treatment, where chlorination is combined with ultraviolet light (UV) for the destruction of contamination by organics. These reactors are routinely operated with the UV lamps receiving 100% power; however this field trial evaluated the effects of adjusting the power to the UV lamps between 50% and 100% on the resulting treatment performance.

Middleton Groundwater Supply in the Region of Waterloo

We used field data to develop a user-friendly model for water quality managers to explore the energy savings at various configuration of treatment operation for AOP, while maintaining treated water that meets and surpasses Ontario Drinking Water Quality Standards (ODWQS). Our research determined the Region could operate the AOP reactors between 65% and 75% power and still maintain high water quality.

Ultraviolet light reactors of the advanced oxidation process (AOP) at Middleton Water Supply System in the Region of Waterloo

So what does this mean for the community of Waterloo? On an annual basis, the Region will eliminate the use of 1,500 mega-watt hours of power consumption—or 575 metric tons of greenhouse gas emissions—which equates to taking 121 personal vehicles off the road or replacing approximately 20,000 incandescent lamps with LEDs.

This is just one example of an energy saving opportunity at an existing facility that is similar to many other treatment plants across the country.

Other benefits from the field study and resulting model include:

  • A better understanding of treatment performance and factors that affect AOP such as temperature, chlorine dose, and flow rate
  • Identification of treatment vulnerability to inform master planning
  • Predictions of water supply impacts that can inform source selection and phasing of groundwater sources
  • Potential for integration with software such as SCADA to provide real-time predictions of treatment performance
  • With an annual cost savings of more than $150,000, this study paid for itself in just 7 weeks

Through our work with the community of Waterloo, we demonstrated that you can achieve a balance between the need for advanced water treatment and energy use through a better understanding of site-specific treatment performance and optimized operations.

         Related item: Water Treatment

Presentations of this project were recently given at Ontario’s Water Conference & Trade Show (OWWA), and at the Canadian Water Network (CWN) Blue Cities Conference where Nicole McLellan won 1st place for the poster presentation competition under the theme of “Pathways to more resilient and sustainable water systems”.

You can achieve a balance between the need for advanced water treatment and energy use through a better understanding of site-specific treatment performance

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