Reclaimed Wastewater for Power Generation

Source: · CANADIAN ELECTRICITY ASSOCIATION · | December 4, 2020

Source: Canadian Electricity Association

The ENMAX Shepard Energy Centre is an 860 MW natural gas-fired combined cycle power generating facility, located at the east end of Calgary. Shepard was built with the goal of providing safe, reliable electricity to Albertans long into the future, with a simultaneous commitment to reducing emissions and using resources responsibly.

By design, Shepard uses reclaimed wastewater from The City of Calgary’s Bonnybrook Wastewater Treatment Facility for all its power generation needs – a first in Alberta. This design feature prevents from having to draw nearly 6 million cubic meters of fresh water from the Bow River every year. Most of the intake water is used in the large cooling tower array, while the remainder is purified in the on-site water treatment plant to be used for boiler water make-up.

Using reclaimed water presents many challenges. From a chemistry perspective, reclaimed water is far more variable than fresh water and contains a large proportion of inorganic and organic compounds. Some of the substances can cause equipment damage. For example, water hardness can cause impurities in water to form solids on machinery, the same way it does in a kettle. Other substances must be kept within strict concentration limits for health and environmental reasons. For some substances, the analytical test methods themselves were found to be influenced by the unique water chemistry, and new sample preservation methods had to be developed.