Getting to Climate Resilient and Low Carbon Urban Water

The Paris Agreement reached Saturday calls for major efforts on technology development and transfer for climate mitigation and adaptation. Urban water management can make a significant contribution to both agendas. How?  Water utilities in Copenhagen, Hamburg, Essen and Amsterdam are showing the way. Over the last decade they have put in place new technologies and adaptation measures that reduce their energy and carbon footprint significantly. How can we get more cities and their utilities on a similar path?

Article 10 of the Paris agreement calls for a technology framework to support the implementation of the agreement by realizing the necessary “Technology Development and Transfer in order to improve resilience to climate change and to reduce greenhouse gas emissions”. It is also to be noted that new funding of 100 Billion USD per year has been pledged during the Paris Conference of the Parties to implement the agreement. Knowing that 90% of climate change impacts are related to water management, I take this as a direct call to the water sector to develop its adaptation and mitigation technologies.

Technologies in water management can support mitigation or adaptation, and in some cases both simultaneously. These technologies present promising opportunities to produce renewable energy, improve water efficiency, encourage low carbon solutions at the utility or household level, or diversify water supply sources.

Renewable energy production in urban water systems has the potential to fulfil most of the energy requirements of the treatment and pumping of the various waters (drinking-, rain-, waste-water). In Evionnaz, Switzerland, a micro-turbine on the drinking water supply provides electrical energy for the equivalent of 425 households. In Hamburg, the energy contained in organic matter is transformed into heat and electrical energy.The digester gas and the sludge are valorized in co-generators and an incineration facility to produce 62,000 MWh/ year of electricity and 80,000 MWh/ year of heat. This strategy, combined with the installation of wind turbines (24,000 MWh/ year) on the property of the utility, results in an energy positive service! The eco-cité of Mousse in Bordeaux uses the surplus of heat from wastewater –which amounts to 450 MWh/year- to cover 83% of the heating and hot water energy requirements of the neighborhood.

As a consequence of climate change, anticipated changes in flow regimes urges us to accelerate the adoption of existing low carbon solutions for water and wastewater treatment, as well as developing new technologies or novel design approaches that improve energy and water efficiency.

At the utility level, low carbon solutions for water and waste water treatment include solar disinfection, mainstream anaerobic treatment, or  anaerobic ammonium oxidation for nitrogen removal. However, utilities can go beyond their traditional boundaries and encourage application of measures at the household level that help us protect our waterbodies, ecosystems and cities against the impacts of climate change.

For example, Paris Sanitation Utility is investigating developing new neighborhoods with urine separation toilets, so that the nitrogen load could be removed from the wastewater to protect the river quality. This technology development brings them to work on what is happening inside the household, to work with architects and urban planners to design neighborhoods with water services that are adapted to climate change and contributing to mitigation.

Measures for mitigation and adaptation reinforce each other when we tackle water efficiency. For example, smart technologies help us reduce leakage from the drinking water distribution network, which not only alleviates pressure on water supply sources, but also reduces energy consumption.

Many water efficiency gains can also be obtained from the application of technologies at the household level. Efficient use of hot water through efficient showerheads and faucets, heat exchangers between the cold water feed and the wastewater from showers and kitchens, as well as using renewable energy to produce hot water can reduce the household level carbon footprint up to 10 percent!

Adaptation technologies may also focus on flood protection with the “sponge city” approach and by investing in natural infrastructure at the basin scale. Adaptation is also about diversifying the portfolio of water supply. Just like an investment strategist would not bet on one source, water managers would need to tap a range of sources such as rainwater, groundwater, surface water. Or even unconventional sources such as re-use water and desalinated water. Where methods are more energy intensive it is important to opt for low carbon energy supplies, and adapt the treatment level to the intended use. The technology development requirements therefore also include developing our new infrastructures with a fit- for-purpose approach, so that waters of different qualities may be used for different purposes in our cities.

As water professionals, we have a major role to play in the upcoming months to elevate the visibility for water in climate policy and action. We can influence the UNFCC technology framework by conveying how water technologies can contribute to meet the targets set in the Paris Agreement. Water agents need to act in unison so that climate funds also “flow” to water solutions, not just to mobility and renewable energy technologies. So let’s continue the Climate is Water initiative (#ClimateIsWater) so that our small individual actions can all contribute to having a big impact. We may call the Paris Agreement a success, only if we all follow up with actions and get cities with their water utilities on the path to climate resilient and low carbon urban water.

Corinne Trommsdorff

CEO and Founder of Water Cities (
Corinne Trommsdorff has close to 25 years of experience working in the water sector. She is CEO and founder of Water Cities, whose mission is to support local stakeholders in their transition towards “water-wise” management based on the I... Read full biography