Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | JANUARY 2017 | 7 Comment I n November, the International Energy Agency (IEA) released its annual report into the state of the global energy industry: the 2016 World Energy Outlook. As part of its comprehensive appraisal of global energy market issues, the 2016 report included a brand new chapter focusing on the water industry – in particular, its huge electricity consumption and the strain this is putting on global energy demand. The interdependency of water and energy – also known as the water-energy nexus – is highlighted as one of the biggest energy issues for the next 25 years. According to the report, the water industry currently accounts for 4% of global electricity consumption – roughly equivalent to the demand from the whole of Russia. This proportion is predicted to rise even further, potentially doubling by 2040 if immediate steps are not taken. With demand for water outstripping population growth by more than double and an increasing number of countries experiencing high levels of water stress, this energy challenge is only going to proliferate unless we find a way to decouple the water industry from energy use and use both resources more efficiently. What's frustrating about the water-energy nexus is that there are technologies already in use that could solve this challenge – we simply aren't deploying them in the right way. Sensors can be used to monitor in real time the amount of water that's being used at any point during the day, analysing everything from flow to pressure in the pipe network. In wastewater facilities ammonium, nitrates, phosphate, etc can be used in real-time to analyse the biological processes too. The data from this can then be used to manage the flow and pressure of water round the network – primarily by using variable speed drives to regulate the speed of pumps and blowers – or to adapt wastewater treatment processes to be more effective. This digitised approach coupled with the use of more efficient components could, it's estimated, reduce the water sector's electricity consumption by up to 40% – a colossal saving when you consider the total consumption is about the same as that generated by both solar and wind power globally. These technologies are neither unique nor particularly high-tech – it's just about deploying them together in the right way to achieve the best results. The city of Aarhus – Denmark's second largest city – is the first place in the world where the local water company, Aarhus Water, has succeeded in achieving complete energy neutrality across the whole water cycle for a catchment area of 200,000 people. Partly this has been achieved through energy efficiency, using advanced process optimisation and sensors linked to variable speed drives. But it has also come from embracing the potential to turn wastewater plants from major energy consumers into energy generators. Using anaerobic digestion technology, the Marselisborg Wastewater Treatment Plant in Aarhus is now a power station in its own right, generating enough energy to cover its own sizeable demands and up to 130% more. The excess electricity is sold back into the grid at a profit to the water company. Excess heat – around 2.5 GW per year – is also sold into the local district heating system, providing another valuable source of income. All of this is without adding carbon from external resources, or using solar or wind energy. For the water company, the return on investment period has been just five years. Meanwhile, the efficiency achieved as a result of these changes has contributed to decreasing water prices for local residents – in stark contrast to what's happening elsewhere in the world. There is huge potential for this approach to be deployed elsewhere. What's needed for it to be replicated, however, is a coordinated suite of policy measures to encourage governments and businesses to embrace the potential offered by energy efficiency. The water-energy nexus is just one part of the global energy challenge. But if we could reduce the water industry's dependency on energy even by half, we would markedly impact global electricity consumption and play a key role in reducing the strain on resources for future generations – not to mention making significant and sustainable cost-savings. Decoupling water from energy use must be a global priority The technology exists to achieve energy neutrality across the whole water cycle, and it should be considered a global imperative Mads WarMing GloBAl DiREcToR of WATER AND WASTEWATER DANfoSS The WWTP in Marselisborg, Aarhus, generates more energy than it uses