Desenvolvimento de metodologia multicritério para avaliação de desempenho de estações de tratamento de esgotos de uma bacia de esgotamento em Fortaleza/CE

Abstract

Wastewater treatment plants (WWTPs) are considered punctual sources of pollution, which can compromise the receiving water bodies when not properly monitored. So, there is a growing need to assess the performance of these facilities to provide technical, economic, and environmental information at a given point in time. The effective and efficient performance of the WWTPs contributes to the sustainable management of water resources, especially in the Brazilian semiarid region, which suffers continually from water lack. In this context, it is proposed to develop a model for evaluating the performance of WWTPs in a sewage basin in the city of Fortaleza, Ceará. Considering this, the Delphi method was integrated with multi-criteria decision support methods to determine the overall performance of these installations in one of the proposed performance categories: “Good”, “Satisfactory”, “Unsatisfactory” or “Bad”. First was selected and proposed the performance of indicators (PIs) that were most appropriate for the evaluation of the study's WWTPs in the environmental and operational dimensions were carried out. Then, the criteria (importance, measurability, easiness of reading and sensitivity) and alternatives (PIs) were assessed through Delphi consultation with decision makers in the context of the WWTPs. The answers given by the experts were used to define the weights of the PIs by the AHP method with ratings and the AIP approach. After the completion of this first methodological step, the TOPSIS-Sort multicriteria method was applied to determine the global performances of the 51 WWTPs of the Rio Cocó drainage basin. According to the results obtained, the technologies with the best COD removal efficiencies, the most important indicator in the AHP ranking with ratings, were Facultative Lagoon followed by Series Maturation Lagoons and UASB. While UASB technologies followed by Submerged Aerobic Filter and Activated Sludges presented the worst efficiencies. As for the sensitivity analysis, the changes in the weights of the criteria practically did not affect the ranking of the WWTPs by type of treatment, indicating consistency of the global performance results obtained by the TOPSIS-Sort method. It is concluded that the developed methodology can be adapted to other types of treatment systems and different scenarios according to data availability. This flexibility helps make sanitation decision-making more accessible and adaptable to the specific needs of each case.