Tecnologias utilizadas nos sistemas descentralizados de tratamento de esgoto sanitário no Brasil

Abstract

The treatment of sanitary sewage in Brazil is still predominantly carried out by centralized treatment systems, in which through extensive networks, sewage is collected and transported to a single Sewage Treatment Station (ETE), usually of large size. However, decentralization represents a more holistic approach, which considers the benefits of reducing the amount of waste at the source and the possibility of maximizing on-site water reuse. However, a major challenge for the implementation of this type of system is associated with the large number of alternatives, in addition to the various aspects that are not always considered when making decisions about the sewage treatment system. Therefore, the main objective of this work was to carry out the description and critical analysis of the main sanitary sewage treatment processes used in decentralized ETEs in Brazil. Special emphasis was given to the use of these processes considering the main environmental, social and economic aspects, based on secondary data available in the technical literature. For the environmental assessment, the criteria of environmental impact, global warming, sludge production, as well as the comparison of data on the efficiency of removal of organic matter and nutrients from the systems were considered. Likewise, the following economic criteria were determined: life cycle cost, operating/maintenance cost, investment cost and required land area. For the social aspect, the criteria of visual impact, participation/acceptance of the population, bad odors, reliability and replicability were considered. Finally, it was possible to conclude that for the criterion of sustainability, the study proposed by Coury (2020) highlighted with greater feasibility the use of the Evapotranspiration Basin technology. As for the reliability criterion, the use of a Sand Filter stands out. Pereira e Souza (2020) for the required area and environmental impact criteria, the most viable technology would be the Septic Tank or Septic Tank, followed by the Anaerobic Filter, as it has a lower cost. For the use of effluent for reuse, the best treatment option, according to Pereira and Souza (2020), would be the Septic Tank followed by MBR and the Septic Tank followed by BAS. The UASB system is the most used in the country, representing 40% of the small ETEs inventoried, as it has positive characteristics for the criteria of operating costs and removal of organic matter. Schroeder (2020) indicated that the most viable alternative would be the Horizontal Constructed Wetlands – WCH, with 25% for a scenario of 150 inhabitants.