The use of simulated whole effluents in toxicity assessments: A review of case studies from reverse osmosis desalination plants

Seawater desalination is an increasingly common means to meet the demand for freshwater. Resulting wastewater discharges can, however, impact biota of the surrounding environment. Concern exists that interactive effects specific to the outputs of each desalination plant may result in unique impacts difficult to predict by studying existing plants or assessing the effects of individual chemicals found in waste streams. Given this, we highlight an alternative approach to assess potential toxicity of desalination outfalls. Specifically, we review three recent case studies from Australia in which simulated whole effluents were used in toxicity assessments before desalination plants were constructed. This approach enabled potential toxic effects of wastewater to be considered before the plants became operational and, in one case, even facilitated consideration of potential effects of different treatment processes and suppliers. As in many whole effluent toxicity assessments, the time required for testing and restricted range of species considered were limitations. Given the benefits of this method, however, the use of simulated whole effluents is a development that could facilitate an improved capacity to forecast impacts of proposed desalination plants. © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

As desalination is increasingly used to alleviate water scarcity, potential exists that this process may impact marine environments. Consequently, new approaches for identifying potential effects and enabling their mitigation are likely to be increasingly desirable. The use of simulated whole effluents allows a variety of hypotheses and models specific to the contaminants and area of interest to be directly assessed, an outcome not possible if using the more traditional methods of forecasting likely impacts of desalination effluent disposal (e.g., considering the impacts of currently active plants located elsewhere or identifying the effects of multiple effluent contaminants separately). While representing an improvement in impact assessments of plants before their construction, our review highlights that these tests remain imperfect with issues largely linked to the WET methods used, specifically the time these tests take to conduct and limited species which can be considered. If the methods applied in such testing continue to improve we anticipate that over time the use of simulated effluents in WET testing will increase. This method could facilitate site-specific investigations and the derivation of relevant local management targets across a wide range of geographic areas for different desalination plants and processes, potentially well before plants are constructed. Given these potential benefits, testing using simulated whole effluents could become an integral component of regulatory approval mechanisms.