The MemEOL tool is comprised of a number of user interaction steps, and background calculations based of these inputs. The tool algorithm uses these inputs to rank the end-of-life options in order of preference.
When using the tool, the user is prompted to provide information about condition of the membranes. The tool also provides links to educational information on the measurement of these parameters. The user is also prompted to rank five assessment criteria(see below), in order of importance to their specific end-of-life program. The tool then uses the data on performance and damage to assess if the membranes are within a suitable range for direct reuse, or chemical conversion and reuse. If the membrane is deemed unsuitable for reuse given the parameters provided, the option is removed from the decision making process. Following these considerations, the tool provides a number of end-of-life options in order of favourability and provides information on these options, along with contact details for providers. If the membranes are deemed suitable for reuse, then further information about their potential applications is provided.
Multi-Criteria Decision Analysis
The tool is based off a discrete multi-criteria decision analysis (MCDA) system. Specifically, the quantitative results such as environmental impact from a life cycle assessment (LCA) and the qualitative information such as public acceptance and project complexity can be combined in a single analysis. This scaling process converts the range of performances of the end-of-life options relative to the assessment criteria to a score between 0 and 1, which can be used by the MCDA tool. For this tool, a value of 0 is the least favourable outcome, and a value of 1 is the most favourable outcome.
The final preparation step in the MCDA process is assigning weights to the assessment criteria. Traditionally, the weights of different criteria are determined through iterative collaboration from the project stakeholders. The MemEOL tool, however, uses a novel dynamic weighting method, to cater for users with different needs. This method relies on the internet based nature of the tool, allowing the user to ranks the criteria in order of importance to their specific end-of-life program.
Assessment Criteria
The MemEOL tool uses simple, non-overlapping, criteria to assess the performance of the end-of-life alternatives for used membranes. The criteria have been selected to reflect parameters significant to the user, and that facilitate comprehensive and meaningful assessment of the end-of-life options, based on the goals of the tool. The assessment scores for the qualitative criteria (financial impact, project complexity and public perception) are determined using the assessment matrix (see Table).
Alternative Decision Matrix
Using the information outlined in the previous sections and quantitative data developed in other chapters, each assessment score has been assigned and normalized. The results of this process can be seen in the normalised decision matrix (Table below). This information which is directly used within the MemEOL tool, can be better visualised for comparison in the following Figure.