Microplastiques dans le territoire toulonnais: occurrence et efficacité des traitements des stations d’épuration

The occurrence of microplastics in the environment is a growing concern. Their presence in the ocean and in sea water has been documented since the early 1970s. The sources of microplastics emissions are numerous and related to human activities. Wastewater treatment plants (WWTPs) are sometimes reported as sources of microplastics while a growing number of studies demonstrate high removal performances of microplastics during wastewater treatment. The first studies focused on microplastics above 300 μm that could be analyzed by simple techniques (optical microscopy in particular) commonly used in laboratories. The development of more powerful analytical tools has led to a lower detection limit of a few micrometers. However, the lack of harmonized analytical protocols (sampling strategy, sample preparation, etc.) still renders the comparison of results from different studies difficult. The MEDIPLAST project studies the occurrence of microplastics in the water cycle of the Toulon metropolitan area using a robust and reproducible analytical method on all the samples. Microplastics down to 10 μm are qualified and quantified in four WWTPs composed with different treatment processes. Measurement campaigns were also carried out in the marine environment at six locations in Toulon bay to assess the impact of discharge from WWTPs or harbor activities. Results show a very good performance of WWTPs with a removal of microplastics higher than 99.4%. The primary treatment is the most efficient step but biofilters and disc filters enable an additional elimination of the remaining microplastics up to 69%. Offshore measurements do not show a significant increase of microplastics at the WWTPs discharge points compared to the aquatic environment not impacted by the discharges.