Tratamento de esgoto utilizando a ecotecnologia Wetlands Construídos para sistemas coletivos de pequeno porte

Abstract

In the national scenario, despite the advances in the sanitation sector, the deficit of access to adequate public services of sewage collection and treatment is still evident, especially in rural communities, due to their particularities that preclude the adoption of conventional and centralized sanitation solutions. In this context, this work presents the design and analysis of two alternatives of domestic wastewater treatment systems, based on the constructed wetlands ecotechnology, in order to evaluate the efficiency, costs and adequacy of the systems to the target locality of this study. The project was planned for the treatment of domestic sewage generated by the community of Ingá located in the rural area of the municipality of Crateús. The alternatives considered for the project were the French system adapted to tropical climates, consisting of Vertical Flow Constructed wetlands (WCFV) units, and the hybrid system, which consists of the association of the 1st stage of the French system and Horizontal Flow Constructed wetlands (WCH) units as post-treatment. The steps performed in the work presented the sizing of the modules, the reservoir for the pumping system, characterization of the systems, as well as the detailing of the modules highlighting the constructive aspects, treatment efficiency, preliminary cost estimation and comparative analysis between the two systems. Based on literature, the modules presented the following dimensions: (i) WCFV 1st stage 294 m2 of surface area; (ii) WCFV 2nd stage 220 m2 of surface area; (ii) WCH 220 m2 of surface area. Regarding efficiency both alternatives presented satisfactory estimates for organic parameter removal, resulting in an overall performance higher than 85% in BOD, COD and SS removal, however, nutrient removal were estimated below 50%. The preliminary cost of the systems differed in almost 16%, being the hybrid system a little more economically attractive, presenting a preliminary cost of R$ 274,26/hab, while the adapted French system corresponds to R$ 321,46/hab. The final decision matrix was more favorable for the French system, given its high efficiency in the treatment of organic parameters and superiority in the treatment of nutrients compared to the second alternative. As well as its greater scientific reliability, due to a greater volume of studies and satisfactory full-scale experiences using this system configuration. It is worth mentioning that the second alternative was promising for future studies, presenting great efficiency and economically advantageous.