One of the challenges of an ever-increasing population and climate change is the demand for fresh drinking water. The International Energy Agency’s World Energy Outlook 2016 estimates that the amount of energy used in the water sector will more than double over the next 25 years. This is especially troubling for developing countries who will need more energy to produce potable drinking water for a growing global population.
A project was undertaken in the small town of Aarhus, Denmark to find a possible solution to this potential crisis. They embarked on becoming the first in the world to distribute fresh drinking water by utilizing energy from waste particularly from the treatment of domestic wastewater and sewage.
The Marselisborg Wastewater Treatment Plant in Aarhus was upgraded so that it can generate energy from waste providing more than 150 per cent of the electricity needs for operating the plant. The excess energy will then be put to good use by pumping drinking water around the city.
Aside from providing the 200,000 residents of Aarhus with clean drinking water from renewable energy, any leftover electricity will be sold to the local power grid.
Danfoss Power Electronics is the company supplying the technology for Aarhus Water, the municipal water utility. “We are about to be the first energy neutral catchment area,” says Mads Warming of Danfoss.
The way the plant generates energy from waste is through the production of biogas, a by-product of wastewater and sewage treatment. Carbon compounds are separated from the wastewater and are fed into digesters that contain bacteria and break these compounds down at temperatures reaching 38°C. The resulting gas that comes out of that process is methane, which can be used to produce heat and electricity.
According to Lars Schøder, general manager of Aarhus Water, there is no need for organic material from restaurants or energy from wind turbines or solar panels to provide additional energy.
The idea of producing biogas from wastewater treatment has been around for some time, but what makes this system work is the combination of strict environmental regulations for water discharge and a mandate for reducing nitrate and phosphate pollution. Also important is the continuous monitoring of the pipes throughout the seasons, to reduce the cost of maintenance and repairs The Marselisborg upgrade will require an investment of nearly €3 million, which Aarhus Water expects to recoup in five years, based on maintenance savings and the sale of excess energy into the grid.
More cities have taken notice of this little experiment in Aarhus. Copenhagen has started to replicate the system for their water needs as well as cities as far off as Chicago and San Francisco in the U.S.
As promising as this project has been for renewable energy for water distribution however, a few challenges need to be overcome. A sizeable investment is still needed for this to be replicated elsewhere, which could raise the cost of water. Also, a large wastewater plant is necessary to have enough biogas to generate a significant amount of energy. The wastewater likewise has to be of the right mix – if it’s diluted by rain or groundwater it will be harder to recover sufficient energy.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us on 1 (877) 479-1388.
Sources:
https://www.iea.org
https://www.newscientist.com