Closed water loop

Closed water loop


08/10/2019 3:32 pm


ESA–SJM Photography


Visitors to ESA’s Open Day in the Netherlands could relieve themselves and quench their thirst in one go, thanks to technology developed for space.

The Semilla Sanitation Hubs’ unit provided toilet and washing facilities that recover and treat wastewater for continuous use. To demonstrate the reliability of the closed-loop system, the visitors could enjoy some tea and associated explanation about the Closed Water Loop.

The unit is based on regenerative life support technologies for astronauts in space developed by ESA’s Micro-Ecological Life Support System Alternative or Melissa project. 

An additional food production unit feeds recovered nutrients for crop cultivation.

Used water, termed ‘grey’ (washing up and showers), ‘yellow’ (urine) or ‘black’ (excrement) depending on its origin, is processed into hygienic water through a cascade of technologies (e.g. filtration). For example, the grey water is forced through a ceramic honeycomb peppered with holes 700 times finer than a strand of human hair, followed by filtering through a pair of membranes.

Diluted water molecules are further filtered out through the process of reverse osmosis, in which fluid is drawn through a membrane that only allows particles of a certain size to pass.

Once the water has passed through the various types of filtration, the procedure ends with UV irradiation to kill the last bacteria and impurities. The water should now be ready for reuse.

Closed-loop systems such as this are vital to long duration space missions. Without recycling a permanent habitation on the Moon or a mission to Mars would be impossible, but it is also much needed on Earth for sustainable growth.

A water recycling system based on Melissa is already in place in remote areas like Concordia research station in Antarctica. The same system was used to treat groundwater for a University in Morocco.

Semilla’s hubs are an example of a space spinoff that is helping to achieve the United Nation’s sixth Sustainable Development Goal of clean drinking water and hygienic sanitation for all.

The commercially available units can be easily installed, making them adaptable for use in first aid and development sites as well as permanent homes.

Reusing water while reducing usage and cost and recovering nutrients is sure to leave a good aftertaste.

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