Degradation and transfer of polyacrylamide based floculents in sludges and industrial and natural waters - Potential impact on aquatic ecosystem: The AQUAPOL project
Résumé
Flocculants are widely used in several industrial fields (mineral extracting, chemical industry, food processing industry, treatment of drinking water) to enhance solid/liquid separation in water containing suspended matter. In France, mineral extracting industry is the major user of flocculants. The use of flocculants enables to increase the recycling rate of process water and to decrease sludge volumes, and thus the surface of settling impoundments. Those impoundments are open system with possible exchanges into the near environment (water percolation towards the aquifers, water seepages in natural stream or rivers...), which can lead to the dissemination of flocculants into surface water and groundwater. The question of flocculants innocuousness is now arising as a new environmental issue. The flocculants which are calling into question are composed of polyacrylamide, a polymer synthetised from acrylamide and acrylic acid. The final product contains residual amount of acrylamide which is classified as a carcinogenic (level 2), mutagenic (level 2) and reprotoxic (level 3) compound. The environmental issue does not concern the polyacrylamide, which is not known as a toxic compound, but the acrylamide and the products of polyacrylamide degradation. Although industrialists and administrative authorities in charge of environment protection regard the use of flocculants as an important environmental matter, there is no scientific and multidisciplinary study which can help them to take appropriate measures to prevent potential impact on the ecosystems. In this context, the global objective of "AquaPol" project is to study the behavior of acrylamide, polyacrylamide and products of polyacrylamide degradation in process and natural waters and their impacts on the balance of aquatic ecosystems. The effort will be put on the particular case study of the mineral extracting industry. The heart of this project will be based upon in situ characterization of the dissemination of polyacrylamide, acrylamide and products of polyacrylamide degradation in connexion with the physical, chemical, microbiological and hydrogeological properties of the studied environments. This study will be surrounded by analytical developments, an eco-toxicological study, a laboratory characterization of transfer and degradation mechanisms and the development of bio-hydrogeochemical model. One of the main purposes is to bring to flocculants users and administrative authorities the scientific basis which can enable them to implement the appropriate measures to prevent potential environmental damages linked to the use of flocculants.