A city in Denmark is about to become the first in the world to provide its citizens with fresh water using the energy created from household wastewater and sewage.
The Marselisborg Wastewater Treatment Plant in Aarhus has undergone improvements that mean it can now generate more than 150 percent of the electricity needed to run the plant, which means the surplus can be used to pump drinking water around the city.
As well as powering the entire water system of 200,000 people living in the inner-city area, any excess electricity can be sold into the local grid.
The plant generates energy from the biogas it creates out of household wastewater, including sewage. Carbon is extracted from the wastewater and pumped into special digesters filled with bacteria and kept at 38°C. These produce biogas, mostly methane, that is then burned to make heat and electricity.
This technology isn’t new but its success in Aarhus is down to a combination of environmental regulations targeting water discharge and a mandate for reducing nitrate and phosphate pollution. Tailored infrastructure for using the recovered energy has helped, as has controlling the daily and seasonal pressure on the pipes, which reduced the revenue lost due to leaks and maintenance costs.
Upgrading the facilities in Marselisborg required an upfront investment of almost €3 million, but Aarhus Water expect that to be recouped in just five years, from maintenance savings and the sale of excess energy into the grid and the district heating system.
Other cities in Denmark, including Copenhagen, have been trying to copy the example Aarhus has set. Other cities around the world, including Chicago and San Fransisco have also shown interest.