GreyWaterSolutions: From Shower to Toilet flush – A Living Lab Case with Aarhus Vand
Challenge
Access to clean drinking water is increasingly challenged by groundwater pollution, including PFAS and pesticides, climate change, and urban population growth. At the same time, a significant share of household water consumption is used for purposes that do not require drinking water quality.
On average, 28% of residential water consumption is used for toilet flushing, creating a structural mismatch between water quality and use. The challenge is to document safe and operationally stable alternatives to using drinking water for low-value purposes.
Solution
In collaboration with Aarhus Vand, GreyWaterSolutions has tested a decentralised greywater solution that addresses this mismatch between water quality and use.
GreyWaterSolutions has developed a decentralised greywater solution in which water from showers is treated and reused for toilet flushing. As part of the Water Living Lab, the solution has been tested to examine how it performs under realistic use and operating conditions.
The treatment process includes, among other things:
- Removal of soap residues and particles.
- Treatment aimed at achieving stable microbiological quality.
- The option of disinfection for further reduction of bacterial levels
Implementation
The Water Living Lab framework has enabled testing, documentation, and technical sparring in collaboration with Aarhus Vand. GreyWaterSolutions has focused on documenting that the solution can operate in a stable, safe, and hygienically responsible manner under realistic use and operating conditions.
The demonstration has provided GreyWaterSolutions with valuable insights that can serve as a basis for further assessing the solution’s applicability and risk profile.
Based on the demonstration project, GreyWaterSolutions identifies potential for the solution in building types with high and stable water consumption, including:
- Sports facilities and swimming pools
- Hotels
- Apartment buildings and offices
- Projects focused on resource efficiency and circular water use
The solution can contribute to reducing drinking water consumption by 30% and thereby support a stable alternative water source for buildings. This can help enable a more sustainable, resilient, and future-proof water supply.
“It has been an interesting exercise for Aarhus Vand to work with GreyWaterSolutions’ solution in the Water Living Lab, with a focus on reducing the use of clean groundwater for purposes such as toilet flushing. New solutions that provide Aarhus Vand with insights into sustainable water consumption are of great interest, both professionally and as part of developing the opportunities within the Water Living Lab.”
– Christian Schou, Head of Projects, Aarhus Vand
About the initiative
The project is part of the Danish Lighthouse for Water Technology and is realized with support from the European Regional Fund and the Danish Board of Business Development. The initiative is implemented in collaboration between Klimatorium, DTU Sustain, Clean, Aarhus Vand, Aarhus University, Lemvig Vand, VIA University College, Denmark’s Environmental Portal, DHI, Tecnological Institute, The Alexandra Institute, Water Valley Denmark, and Erhvervshus Midtjylland.
