In 2023, a US engineer put a miniature water-treatment plant beneath the sink; the under-$500 unit converted 20% of household greywater into drinking water

A small space beneath a kitchen or bathroom sink is usually occupied by pipes, cleaning supplies and little else. In 2023, however, young US designer and engineer Noemi Florea was developing a different use for that overlooked space: a compact treatment system capable of treating household greywater to drinking-water quality. According to UNICEF, Noemi Florea developed Cycleau as a compact household water-treatment system designed to fit beneath a sink and recycle greywater into potable water. The system was selected for UNICEF's Innovation30 programme in 2023 and was intended for use in homes, remote schools and healthcare facilities. UNICEF said Cycleau could cost less than US$500 per unit and recycle 20% of household greywater into potable water, while reducing the discharge of untreated wastewater.Turning used water into a resourceGreywater usually comes from domestic activities such as washing, bathing and laundry, rather than toilets. Although it is different from sewage, it can still contain microorganisms, chemicals and other contaminants, meaning it cannot be considered safe to collect and drink without treatment. Cycleau was designed to combine multiple water-treatment techniques within a single compact device. The system could be connected to existing water and drainage pipes serving a sink, bathroom or laundry area, allowing some of the greywater that would otherwise flow directly into the sewage system to be diverted for treatment and reuse.As Florea developed the concept, the technology became more refined. According to MIT Solve, the system was being designed as a modular, point-of-use treatment unit measuring roughly 24 by 36 inches. It was intended to capture greywater and treat it on site, while also addressing concerns about contaminants in household water supplies. The treatment train combined several methods rather than depending on a single filter. That layered approach reflects a basic principle of potable water reuse: different treatment processes are used to tackle different types of contaminants. Research published in Water Research examined decentralised greywater treatment using membrane bioreactors and moving-bed biofilm reactors followed by ultraviolet or electrochemical disinfection. The study found that combining biological treatment with disinfection could provide effective treatment while also highlighting the different strengths and limitations of each process.The promise and limits of decentralised treatmentThe appeal of a system such as Cycleau lies in bringing water treatment closer to where water is used. Rather than sending all household wastewater through a central network, a compact unit could divert and treat a portion of it for potential reuse. This approach could be useful in places where conventional water infrastructure is expensive to build or difficult to extend. UNICEF identified homes, remote schools and healthcare facilities as potential settings for Cycleau, particularly in communities facing water shortages or limited access to reliable water services.However, Cycleau was still an emerging technology in 2023, rather than a proven replacement for conventional drinking-water treatment. MIT Solve reported that the team was developing and testing automated prototypes and planned further evaluation of their ability to remove contaminants. Early testing also came with an important limitation: volunteers were instructed not to drink the water produced by the prototype. The technology therefore still required further testing and validation before it could be considered suitable for producing water for household consumption.From prototype to wider water reuseAccording to UNICEF, Cycleau had moved beyond the Innovation30 demonstration phase and entered a pilot project in collaboration with UNICEF in Tajikistan. In 2024, UNICEF stated that installing Cycleau in buildings could reduce their water footprint by up to 80%. This figure referred to the potential reduction in overall water use associated with the technology, rather than meaning that Cycleau could collect and reuse 80% of a building's greywater. Its underlying concept was to treat and recycle water that would otherwise have been discharged, potentially reducing the need for fresh water from conventional sources. However, the amount that could be recovered and reused would depend on the building, the installation and how the system was operated. For communities facing water shortages, the appeal was therefore not simply in treating wastewater, but in creating another opportunity to reuse water close to where it was originally consumed. Instead of relying entirely on additional supplies from reservoirs, rivers or aquifers, some of the demand could potentially be met by water already flowing through the building.Catch the latest World News and Live updates. Download the TOI app.