https://www.nature.com/articles/s41545-024-00343-4

For over a century, centralized wastewater treatment has dominated urban sanitation. This approach relies on sewer systems to transport wastewater from cities to large, linear wastewater treatment plants (WWTPs) that prioritize pollutant removal over resource recovery. This has inherent limitations. To this day, only 11% of treated wastewater is recycled1, and very little of its energy potential is captured2. The main technology, activated sludge, is an extremely energy-hungry process designed to destroy valuable nutrients instead of recovering them3. This process not only consumes about 1–3% of the United States of America global electricity and is a major source of greenhouse gas emissions (0.18 to 0.98 kg CO2e per cubic meter of wastewater treated)4, but also removes nitrogen (rather than being recovered as fertilizer) while 90% of phosphorus gets trapped in biosolids5. Even if the large amount of produced biosolids that need to be costly treated can eventually be used as fertilizer, they represent a fraction of recoverable nutrients, requiring complex transportation and retaining about 90% of all the microplastics captured in the sewer (up to 1% by weight)6, so the widespread practice of using biosolids as fertilizers can contaminate soil and our daily crops with microplastics7.