Comparação de métodos de cálculo de redes de esgotamento sanitário: estudo de caso

Abstract

Sanitary sewer systems are an essential component of basic sanitation, being responsible for the collection, conveyance, and proper disposal of wastewater generated in urban areas. The hydraulic performance of sewer networks depends on the appropriate definition of design parameters, topographic conditions, and the calculation procedures adopted during the design process. In this context, this study compared two hydraulic design methods for sanitary sewer networks by applying them to a sewer system designed for a selected area within the Ismail Aziz Community, located in Manaus, Amazonas, Brazil. The comparison aimed to evaluate their performance regarding hydraulic parameters, compliance with design standards, and the technical implications of their application in engineering projects. To ensure a consistent comparison, both methods were applied under identical design conditions, maintaining the same network layout, pipe diameters, slopes, design flows, and other hydraulic parameters. The results showed that both methods produced equivalent hydraulic designs with respect to the depth-to-diameter ratio (Y/D), flow velocity, and pipe diameter selection, fully complying with the requirements established by the Brazilian standard ABNT NBR 9649 for these variables. The differences were concentrated in the evaluation of shear stress, the parameter directly associated with the self-cleansing conditions of the sewer network. The second method demonstrated greater sensitivity in identifying hydraulically critical conditions operating close to the minimum design limits established by the standard. It is concluded that the use of a continuous analytical formulation for determining the depth-to-diameter ratio preserves the hydraulic consistency of conventional sewer design while improving the reliability of self-cleansing verification under critical hydraulic conditions, representing a technically consistent alternative for supporting the hydraulic design of sanitary sewer networks.