To reduce pollution along the Mediterranean coast

Macrowaste is made up of persistent solid materials, transformed or manufactured by humans and lost, discarded or purposely abandoned in the natural environment, ending up in marine habitats. Every year, more than 10 million tonnes of macrowaste are dumped in the marine environment. 80% of this waste is land-based, the remaining 20% comes from marine activities such as transport, fishing, fish farming, etc. It is estimated that 15% is dumped on beaches - the most obvious sign of this form of pollution - while 15% floats on the surface and the majority - 70% - is deposited on the sea bed.

In the Marseille-Provence region, some of this macrowaste comes from urban areas situated in the catchment basin. Drainage systems therefore play a key role in transporting waste to the sea.

A six-stage approach

A number of new technologies are helping to fight the presence of macrowaste along the coastline by intercepting it before it reaches the natural habitat - nets at drainage outlets, inlet baskets, screens - but they often have a limited impact or reduce the hydraulic efficiency of the network.
This calls for an approach specially designed for the region

From December 2019 to May 2021, SUEZ Consulting conducted a pilot study in six stages:
1. Define the region's specific challenges
2. Distinguish types of macrowaste in the networks
3. Identify pertinent sites for capture devices
4. Co-build a trapping strategy with the contracting authority and its operator
5. Determine the feasibility of the chosen sites
6. Plan for the devices to be fitted in the system

The results

Under the contracting authority of Marseille's Department for Water, Sanitation and Drainage, analyses enabled us to develop a tool to quantify macrowaste for each catchment basin, then to choose the best sites to install devices:
  • 80 drainage outlets, 7 basins and 15km of open networks visited
  • 80km of underground networks analysed using GIS
  • 102 potential sites identified and analysed according to different criteria
  • 15 sites underwent detailed feasibility studies for installation of a trapping device
  • 7 different technologies proposed for the different devices analysed in the detailed feasibility studies
The pilot study conducted in Marseille enabled us to define a macrowaste trapping strategy suited to the region's specificities to protect the natural habitat.
Olivier Knapen , Director of Urban Water and Environment at SUEZ Consulting