Contribution to the study of seawater desalination effluents: chemical and toxicological analysis of a discharge after using a mixing basin (Martinique)

Oil production and refining require very large quantities of fresh water. Therefore, the use of unconventional methods to exploit resources, such as seawater desalination, appears to be an interesting alternative to produce a controlled and conditioned quantity of water to meet the required quality for its use. In this context, the French Company “Société Anonyme de la Raffinerie des Antilles (SARA)”, as being the main industrial consumer of fresh water in Martinique, became interested in this mode of production and implemented a project to build a seawater desalination unit. However, seawater desalination generates a discharge of brine concentrate that, by its nature, could lead to environmental problems in the surrounding aquatic environment. To minimize the effects, several measures were taken in the design of the unit, in particular the installation of a mixing basin to dilute the concentrate prior to discharge. The purpose of this study is to assess the potential chemical toxicity of this effluent. The physico-chemical composition on 32 selected parameters as well as toxicity tests using controlled and standardized marine aquatic biological models (Aliivibrio fischeri, Phaeodactylum tricornutum, and Crassostrea gigas) are presented. No chemical elements of concern are observed for the effluent. Moreover, no toxic effect is observed under the conditions of salinity tolerance of the model organisms. These results suggest that the effluent generated by the SARA desalination unit does not present any demonstrated ecotoxicity under the studied conditions. This original work constitutes the first toxico-chemical evaluation study of discharge after dilution in a mixing basin.