An integrated "process modelling-life cycle assessment" tool for the assessment and design of water treatment processes
Résumé
The application of Life Cycle Assessment (LCA) to the design of water treatment plants is hampered by: (1) a large diversity of unit processes, (2) the high variability of the operation conditions in relation with the water quality input, and (3) the range of possible technical solutions to fulfil the treatment needs. For a consistent prospective assessment, the LCA should be based on the simulated functioning of the unit processes rather than on average data, as it is most often the case when no real data are available. Here, a novel, integrated and flexible process modelling-life cycle assessment (PM-LCA) tool for design and LCA of water treatment technologies is presented. The tool (EVALEAU) was developed in UmbertoA (R) (v5.5) using the Python language for code scripting. A library of unit process (UP) modules was built. Each module is a detailed and highly parameterized model of a specific water treatment process, which is further linked with the software PHREEQCA (R) for water chemistry calculation. Input data are: water composition, design, operation parameters, including literature or user-defined values. The modules are linked to Ecoinvent datasets (v2.2) for background processes. By combining the modules, water treatment chains can be designed and evaluated in UmbertoA (R) with a high level of detail and specifications. A sensitivity analysis toolbox (Morris method) was included for the identification of the process parameters mainly affecting the impact results. The tool was successfully applied to the test bed case of an existing drinking water plant located in the Paris region. The conventional LCA results, based on average recorded data, were compared with the results obtained using the PM-LCA tool. Modelling results for technical parameters were also compared with data collected on site. An overall good agreement between simulations and real data was obtained, proving the relevance of the developed tool. Sensitivity analysis indicated that ozone production and transfer into water are the main technological parameters influencing climate change (taken as example since it is of high interest for stakeholders), which have therefore to be fine-tuned. The EVALEAU tool successfully solves the challenge of linking LCA results to the related engineering design choices, from the assessment and eco-design perspectives. The concepts and methodologies embedded within the tool provide the user with complementary views of the designed system, in terms of potable water quality, design and operation parameters and environmental impacts generated over its life cycle.