Reuse and valorisation of Wastewater - Challenges, Issues, and Prospects

Water reuse (treated wastewater, rainwater, graywater, industrial water, etc.) is emerging as an essential solution to address the growing challenges associated with water resource management and usage. In a context marked by climate change, population pressure, and the increasing scarcity of water resources, this practice is part of a transition toward a circular economy and sustainable resource management. It involves repurposing non-conventional water—derived from domestic, industrial, or urban processes—by giving it a second life for various uses: agricultural irrigation, urban cleaning, industrial cooling, and even the production of drinking water.

In environments where water supplies are particularly limited, such as polar stations, submarines, and spacecraft, water reuse is an absolute necessity. These closed systems rely on sophisticated recycling processes to ensure the self-sufficiency of their occupants.

At polar stations, where access to drinking water is extremely difficult due to climatic conditions, water used for drinking, toilets, and washing is constantly recycled and purified. Submarines, because they are confined underwater, are also forced to reuse the water on board for various purposes, thanks to advanced filtration systems. Similarly, aboard spacecraft, astronauts recycle water from their daily activities (urine, sweat, cooking water) to convert it into drinking water, thereby ensuring the viability of long-duration missions, such as those on the International Space Station (ISS).

Long held back by strict regulatory constraints and societal resistance, wastewater reuse is now reaching a major turning point. Recent reforms, at both the national and European levels, have relaxed usage requirements and expanded the scope of application. The decree of August 29, 2023, the 2024 ordinances, and European Regulation 2020/741 have laid the groundwork for a more flexible framework, based on a health barrier approach and risk assessment. Furthermore, the French Water Plan launched in 2023 aims to increase the number of reuse projects to reach 10% of REUT by 2030, compared to less than 1% currently.

The applications are numerous and rapidly expanding: agriculture, green spaces, industry, non-potable domestic uses, and even the production of drinking water in certain contexts. Added to this is the recovery of byproducts from wastewater treatment plants (WWTPs), particularly sludge from water treatment, which can be repurposed as fertilizers, construction materials, energy sources, or raw materials for biotechnology. These prospects pave the way for integrated and multifunctional water management, where every water flow can be optimized.

However, this trend raises several issues:...