Understanding the interdependency of water and energy.

Image by Scott Oves | flickr.com

Image by Scott Oves | flickr.com

Everything is connected—a concept not often denied, though often neglected.

The inter-dependency of water and energy is incredibly important. Potable water supplies require vast amounts of energy. Most developed countries have the infrastructure to pull water from the source, treat, and then deliver it.

On a daily basis, these systems use the same amount of energy required to heat every home in Canada for a day. Not to mention the fact that the delivery of water to consumers’ taps necessitates pressure being maintained throughout the system. More than half of the energy used by water services in Ontario is used to power pumps and related infrastructure, and 60% of the energy used for water services in Ontario is used by the residential sector. This feat is achieved with the use of pumps -- if you’ve ever carried a 20-litre bucket of water, you’ll know water is heavy!

The systems are designed for the delivery of potable water, but also for taking away wastewater from every household and business. The concept of direct water reuse presents an opportunity to reduce the pumping and associated energy costs of domestic water usage.

Here, water down the drain is reused for other household purposes. For example, “wastewater” from washing machines and showers can be used to flush toilets, rather than being pumped all the way back to the central wastewater treatment plant, discharged, and treated again, just to flush waste down a toilet. Direct water reuse challenges “the way things have always been done”, and leads us towards a more eco-friendly and efficient usage model for a very precious resource.

How we phrase ideas definitely impacts public perception. For example, the “yuck factor” associated with reusing water from one purpose to another can turn people away. I propose we do away with the term “wastewater” altogether, and come up with more adequate names that better represent the opportunities that can be harnessed when these waters are reused.

How much water is consumed per unit of energy produced? Well, it turns out that energy production does not consume all that much water; however, the water withdrawn or the water “footprint” required to produce various types of energy varies widely.  Several water footprints are as follows (in gal/MWh in 2012) and these values make renewable energy options stand out:

  • Hydroelectric: 440,000

  • Coal: 16,052

  • Nuclear: 14,811

  • Natural Gas: 6,484

  • Solar Thermal: 800

  • Geothermal: 700

  • Photovoltaic Solar: 231

  • Wind: <61

Understanding the water-energy nexus can help to inform innovations for new conservation technologies; and also optimize the output of existing technologies. To take the conversation further, we can consider the additional connections between water and energy with food and the economy. How much energy and water do you think it takes to make an apple, or a steak? Find out here. Then, calculate your water-energy-food nexus footprint here; this may help you to make decisions about your energy usage.