As the world population increases and people pursue higher standards of living, more water is needed in homes and for production of food and products. In fact, by 2050, the UN projects global water demand will increase by 55%. However, fresh water supplies are limited, and groundwater, which is the source of drinking water for at least half of the global population, is used faster than it is replenished. In just 10 years, 50% of the world’s population is expected to live in water-stressed areas. This increasing demand for water leads to growing energy consumption, which consequently affects climate.
The World Economic Forum has ranked water scarcity and climate change among the top five global risks.
Fortunately, solutions exist today to help countries and municipalities worldwide save water and energy in water supply, wastewater treatment and irrigation of farming areas. For example, Denmark is becoming one of the pioneering countries in the water and energy field. The country has grown its economy by 80% since 1980 while reducing water consumption by nearly 40% and keeping energy use at the same level. Structured water management and innovative technologies have contributed to this decoupling of economic growth, water consumption and energy use.
1. Wastewater
In municipalities, water and wastewater facilities account for the largest consumption of electricity — typically 25-40% of the local authorities’ total power use. In Aarhus, Denmark, a local water company has transformed a wastewater facility into a combined heat and power plant, delivering an energy surplus. The plant produces 134% more energy than it consumes. The excess electricity is sent back to the grid and excess heat is led into the city’s district heating system, further reducing its carbon footprint. This is possible thanks to advanced process optimization and by using more than 290 variable speed drives as control handles on almost all rotating equipment for both reducing energy needed for the processes and increasing energy production. Done optimally, this also creates the maximum amount of sludge and carbon. In a digester, it is transformed into gas used for both electricity and heat production. The surplus energy is also enough to cover the need for energy on the drinking water side and so creates the first energy neutral water cycle for 200,000 people. Scaled up, this example means that water and wastewater facilities could avoid all or much of their energy consumption, turning the single largest electricity consumer in municipalities into an energy-neutral party.
The Aarhus case has attracted attention in cities worldwide. At the beginning of 2015, Aarhus Water signed a cooperation agreement with the water supply company in Chicago (MWRD), which faces the
same kind of challenges and pursues the same goals. With the agreement, they have started to share knowledge about water technologies and climate adaption and energy neutrality, in particular.
If the Aarhus case were replicated on a global scale, the energy saved would be equivalent to the current electricity production from all renewable energy sources combined (excl. hydropower).
2. Reduce water loss
There is also significant potential in the reduction of water losses due to leaks in water supply and irrigation pipes. According to consulting firm McKinsey, $167 billion is wasted every year due to leakage in cities around the world. The UN highlights that leakage rates of 50% are not uncommon in urban distribution systems. However, leaks can typically be reduced by 30-40% by using technologies like variable speed drives and sensors, which control the pressure in the pipes to avoid water flooding out of holes. At the same time, the drives can save 20-50% of energy consumption.
3. Potable water
For water-stressed areas of the world and remote locations like islands, drilling platforms and cruise ships, having a safe potable water supply can impact health and economy. Through solutions like advanced high pressure pumps and energy recovery devices for desalination systems can help to efficiently turn seawater into drinking water — in some cases while saving up to 50% on energy. This is critical as at least 70% of the total cost in desalination systems is related to energy use.
Globally, a focus on the high energy consumption of water and wastewater cycles is increasing, and regulations are starting to expand the use of energy-efficient solutions. The U.S. Department of Energy has proposed minimum efficiency regulations for clean water pumps. Regulations like these are necessary to speed up the realization of the enormous potential.
DOE has estimated that critical processes in water, wastewater and irrigation combined use more than 55 billion kilowatt-hours annually. For U.S. municipalities, rising energy costs play a significant role in water and wastewater treatment services. Plus, a plant’s ability to treat, use and deliver water efficiently — reducing water loss — also has a direct impact on a plant’s energy consumption and bottom line.
Solutions like variable speed drives can address the interdependency of water and energy by providing intelligent pump control to match the motor’s workload more precisely and assisting with constant pressure control schemes that reduce water loss through flow compensation. This technology has proven to save municipalities as much as 3-10 billion kilowatt-hours each year.
