Modelo de seleção de sistemas de tratamento de esgoto sanitário descentralizados para municípios de pequeno porte.

Abstract

The precariousness of sewage services, especially with regard to the treatment of effluents, is a reality in Brazilian municipalities. In small municipalities, the problem is accentuated by technical and financial limitations, making it essential for treatment technologies to be simple, sustainable, economically viable and socially accessible. Thus, this work aims to propose a selection model for decentralized sanitary sewage treatment technologies for small municipalities, with the help of PROMETHEE II, based on the prioritization of technical, environmental, economic and social criteria from the characteristics of sewage basins. In the urban area of the main district of Casserengue, a municipality chosen for the study, the results showed that the technologies constructed wetlands (A2) and the vermifilters (A3) occupy the best positions in the sewage basins, generating no sludge and presenting the highest rates efficiency of biochemical demand for oxygen and suspended solids removal. These alternative technologies have superiority in relation to the selected social and environmental criteria, prioritized by the decision makers, in comparison with the conventional system of anaerobic pond + facultative pond. The alternative A4 (septic tank + anaerobic filter) had a worse position in the ranking of the studied basins. The robustness of the method and the preference given to the criteria for basins with different classifications, indicate that the model is replicable for small municipalities. The work contributes to the optimization of decision-making for sewage treatment systems, providing better use of resources, reducing vulnerabilities, as well as municipal development.