Environmental impacts of water treatment solutions are therefore assessed. Two levels of scales are investigated. First, the effect of water treatment processes on the actual toxicity of effluent is evaluated with the Whole Effluent Assessment (WEA) methodology. Then, a more holistic and macro scale assessment is performed in order to compare the water treatment options planned in different factories (considering different environmental impacts: water pollution but also carbon footprint or impact on human health, considering the whole life cycle of water treatment processes). Methodologies used for this macro-scale assessment are Life Cycle Assessment (LCA) and water footprint.

Regarding effluents toxicity assessment, the historically used substance-by-substance approach presents shortcomings (limited number of substances analyzed, combined effects of substances not considered, etc.). For this reason, WEA is recognized as the most accurate approach for effluent toxicity assessment. WEA is applied to three case studies: chemistry (Pertsorp), textile (Tekstina) and paper (Hamburger Rieger). In all three sectors, WEA shows that the evaluated treatment sequences typically resulted in a reduction in overall toxicity. In the chemical sector, the total toxicity of the conventional activated sludge effluent sample is already quite low and it is thus difficult to quantify toxicity reduction in comparison with other tested technologies in the treatment train. In the textile sector, particularly the MBR treatment results in a strong toxicity reduction, while AOP treatment has an opposite effect. Contrary to the results for the textile sector, anaerobic treatment has a major positive effect on wastewater toxicity in the paper sector.

LCA and water footprint are applied to three case studies: food (CHS), textile (Tekstina) and paper (Hamburger Rieger). Results show that implementation of reuse generally leads to a reduction of the water footprint, but on the other hand to an increase of other environmental impacts (carbon footprint, impacts on human health, etc.) because of additional energy and chemicals consumption and sludge production. In order to mitigate environmental impacts of water treatment processes, it would be more efficient to reduce energy and chemical consumptions of processes, or to valorize sludge. Ensuring that the water finally discharged into the environment reaches an acceptable quality, is also essential regarding environmental footprint. Results also shows that implementing reuse in places where the level of water stress is low, such as the Basque country or the south of Germany, does not necessary make sense as it could generate additional water abstraction in area where the water stress is higher (e.g. south of Spain) in order to produce the additional energy and chemicals required.

Finally, this study demonstrates the applicability and the usefulness of these recent environmental assessment methodologies. Both could help decision makers to better understand implication of water treatment system improvements in term of environmental impacts mitigation, at a local level (through WEA) and global level (LCA and water footprint). Particularly, WEA and LCA / water footprint should be considered as complementary tools. Although WEA demonstrates the usefulness of water treatment solutions for toxicity reduction, it is essential to consider these water treatment solutions improvements in a broader context of environmental impacts through LCA. On the other hand, LCA and water footprint present clear limitations for effluent toxicity assessment that could be addressed through WEA. Links between these tools should be investigated in the future.

If you are interested to read the complete summary: Aquafit4Use - Evaluation of water stress of selected cases

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