Engineered Ecosystem for Decentralized Treatment of Sewage from Small Generators and Isolated Communities

Abstract

In different regions of the world as well as in many parts of Brazil, high percentage of thepopulation and sometimes, entire isolated communities do not have access to seweragesystem or sewage treatment. The common scenario is the use of septic tanks and, in manycases, direct discharge into water bodies. The objective of this study was to develop and test alow-cost sewage treatment system, appropriate for isolated or poor communities at the sametime, meeting the discharge threshold limits established by the Brazilian regulation. For that, acompact engineering ecosystem for decentralized treatment of domestic sewage wasconstructed and tested in a research unit installed in an environmental protected area inGrande Island, south coast of Rio de Janeiro State. The system is formed by septic tank,submersed aerated filter, secondary decanter, and for polishing, vegetated tanks containingaquatic macrophytes (wetland) and one tank with algae. The results of a 200 day monitoringperiod, covering two different flows rates (200 L.h-1 and 52 L.h-1) are presented. With thelower flow (52 L.h-1), the following removal efficiency was achieved: 87.8% (nitrite); 71%(nitrate); 47% (Ammoniacal nitrogen); 89% (COD); 40.2% (total phosphorus). After the flowreduction, most of parameters analysed, met the threshold limits established by the BrazilianFederal Legislation, which demonstrated that the system fulfilled its purpose. ; In different regions of the world as well as in many parts of Brazil, high percentage of thepopulation and sometimes, entire isolated communities do not have access to seweragesystem or sewage treatment. The common scenario is the use of septic tanks and, in manycases, direct discharge into water bodies. The objective of this study was to develop and test alow-cost sewage treatment system, appropriate for isolated or poor communities at the sametime, meeting the discharge threshold limits established by the Brazilian regulation. For that, acompact engineering ecosystem for decentralized treatment of domestic sewage wasconstructed and tested in a research unit installed in an environmental protected area inGrande Island, south coast of Rio de Janeiro State. The system is formed by septic tank,submersed aerated filter, secondary decanter, and for polishing, vegetated tanks containingaquatic macrophytes (wetland) and one tank with algae. The results of a 200 day monitoringperiod, covering two different flows rates (200 L.h-1 and 52 L.h-1) are presented. With thelower flow (52 L.h-1), the following removal efficiency was achieved: 87.8% (nitrite); 71%(nitrate); 47% (Ammoniacal nitrogen); 89% (COD); 40.2% (total phosphorus). After the flowreduction, most of parameters analysed, met the threshold limits established by the BrazilianFederal Legislation, which demonstrated that the system fulfilled its purpose.