In Brazil, there is low coverage of sewage collection and treatment, a condition that is even more critical in smaller cities. One reason for this is the lack of resources for investment in conventional reactors. The present study therefore compared the costs of different treatment alternatives based on the average values of construction and operation present in the literature, the values of the price per square meter for land acquisition, electricity tariffs, and final sludge disposal by considering different operating times of wastewater treatment plants (WWTPs). This allowed inferences about the costs associated with the choice of the configuration of a municipal WWTP. Based on the scenarios studied, it was observed that the conventional systems evaluated are, in general, more costly, especially after several years of operation. However, the choice of these treatment units may be more interesting in scenarios with high cost per square metre and lower electricity rates or where there is no area availability. For smaller cities and with lower real estate pressure, the natural systems evaluated are more indicated due to the low total costs (construction and operation) and adequate pollutant-removal efficiencies. Keywords: choice of wwtp, methodology of choice sewage treatment, natural systems, treatment costs.