Un "Plan Eau" pour aider l’outre-mer à traiter les eaux usées

• In the DROM, domestic wastewater sanitation is managed by: • local authorities such as municipalities or groups of municipalities (wastewater collection networks, treatment facilities); • private individuals or groups of individuals. • Once treated, water flows into rivers, lakes, seas and oceans, soil and groundwater. Ecosystem health is therefore linked to: • the efficiency of wastewater treatment systems; • compliance with regulations (equipment conformity, treatment capacity based on water volume, etc.).

• In the DROM, the proportion of the population not connected to a treatment plant often exceeds 50%. Living standards prevent residents from investing in an effective sanitation system or its maintenance. Almost all existing individual systems do not function properly. • With the exception of Réunion, half of collective installations do not comply with regulations due to problems in managing public sanitation services (difficulty collecting bills, adaptation to growing populations, etc.). • The DROM are often islands with salt-rich atmospheres or emissions from decomposing algae such as sargassum. This further promotes corrosion of sanitation equipment.

Beyond ecosystem degradation, there are other consequences: odor and visual nuisances, difficulty producing drinking water at reasonable cost, negative impact on tourism, etc.

• For all these reasons, the "Water Plan DROM" was established in 2016. • The Water Plan aims to: • strengthen the governance of local authorities; • develop their technical and financial capacity; • improve maintenance and upkeep services; • integrate water policies into territorial planning. • It commits public authorities by supporting local authorities through financial resources, engineering, training, studies and expertise. • It is addressed to: elected officials, administrations, public institutions, consultation assemblies, public financial institutions, etc. • Within the Water Plan framework, overseas local authorities have the option to sign a "progress contract." This is a five-year agreement signed between the State, local authorities and partners to improve water quality and sanitation. Each contract serves to: • plan investments; • pool financing; • organize dialogue among different stakeholders; • fund studies to properly prepare and carry out the project.

• Mayotte offers a striking example. • In 2021, only 19% of Mahorais households were connected to collective sanitation (81% in mainland France). • In 2022, 67% of treatment plants handling wastewater from over 2,000 residents did not comply with legal requirements. • Thanks to the progress contract: • construction of a new treatment plant, which will handle wastewater from 60,000 residents, began in Koungou in August 2023; • the first stone of a future treatment plant was laid in Mamoudzou Sud in May 2025.