Proposta de sistema de esgotamento sanitário para o município de Riacho de Santana/RN.

Abstract

Despite being ensured by law, basic sanitation in Brazil is still very precarious, especially when it comes to sanitary sewage. Many cities do not have a Sanitary Sewage System (SSS) capable of collecting, treating and adequately disposing of domestic effluents, a case observed in Riacho de Santana/RN, which due to the absence of a SSS ends up using inefficient solutions, such as rudimentary cesspits, or discharging effluents in inadequate areas without any treatment. Given this situation, the present work aimed to propose an SSS for the city of Riacho de Santana/RN, composed of all the elements necessary for the collection, transport, treatment and final disposal of effluents. Initially, the current sewage service of the municipality was characterized, through on-site visits and data collection from the Secretaries of Works and Urban Services and Agriculture and Environment. For the project development, first a population study was done, considering a 20 year useful life, and topography of the urban area of Riacho de Santana/RN, followed by the dimensioning of the collecting system and the Effluent Treatment Station – ETS (grating, desander, Parshall flume, UASB reactor, drying bed and polishing ponds). Finally, the best site for the implementation of the ETS and the body to receive the treated effluent were defined. The collecting system was designed to serve the entire urban area through gravity flow, consisting of three drainage basins that together add up to a length of 11630,48 m. The treatment system showed excellent estimates of efficiency. The UASB reactor achieved good BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) removal capacity, reaching the standard required by environmental legislation. Moreover, the polishing ponds ensured high estimates in the removal of fecal coliforms and helminth eggs, allowing the disposal of treated effluent into class 2 water bodies. The site indicated for the implementation of the ETS presents favorable conditions for its execution, operation and maintenance over the years, besides being close to the Santana river, defined as the receiving body.