**7. Conclusions**

It is important to highlight that if carefully performed, sensibility analysis serve as a tool for quality assurance for either of the activated sludge modeling frameworks stated in this review, including refinement of them. The main conclusions of this research are summed up as follows.

The sensitivity indices are in function of the project modeling objectives and the scenarios being evaluated. Consequently, data quality is essential as the model will reproduce it, so if non-valid data are reproduced, will spoil sensitivity analysis applicability.

There are still knowledge gaps due to uncertainty in the influent fractions given the inherent variations in wastewater composition, as well as for the application of global sensitivity analysis that consider factor interaction as almost half of the research outputs conducted a local analysis. The latter is only applicable for assessing linear models, thus, within the activated sludge modeling field, global approaches provide more accurate measures, especially variance-based methods.

Due to the current move beyond water sanitation to resource recovery, it is expected that number of research outcomes concerning sensibility analysis in phosphorus removal models, benchmarking frameworks, membrane bioreactor models, and modification of these will increase. Finally, the sensitivity analysis are capable of propagation uncertainty among the activated sludge modeling framework parameters. Hence, its capability to improve process understanding leading to innovative solutions.
