Assessment of ecological risks linked to the discharge of saline industrial effluent into a river.

Discharges of saline effluents into rivers can lead to risks for local aquatic ecosystems. A specific ecological risk assessment methodology has been developed to propose a management tool to organisations responsible for managing rivers and industrial companies producing saline effluents. This methodology involves the detailed description of the spatiotemporal system concerned, the choice of ecological targets to be preserved, and the performance of bioassays adapted to each of the compartments of the river. Following development, it was applied to an industrial effluent in eastern France. For the scenario studied, results obtained suggest a high risk for the organisms of the water column and a low risk for the organisms of the periphyton. This difference can be explained by the structure of the latter which integrate extracellular polymers secreted by the organisms of the biofilm, forming a gel with a porous structure that acts as a barrier to diffusion. The methodology formulated permitted identifying the critical points of the spatiotemporal system studied and then using them as the basis for making well-grounded proposals for management. Lastly, proposals to improve the methodology itself are made, especially concerning the integration of the sediment compartment in the version formulated initially.