Tratamento descentralizado de efluentes sanitários por sistema de tanque séptico econômico seguido por tanque de evapotranspiração

Sanitation services in rural areas and urban periphery in Brazil are still precarious. In these localities, sewage is discharged into drainage ditches or near of fresh water courses, which can cause groundwater and surface water contamination, imbalances of natural ecosystems and impacts on human health. This work aimed to sized, implanted and evaluated a unit of sanitary effluent treatment formed by an economic septic tank (TSE) combined with an evapotranspiration tank (TEVAP) cultivated with banana trees (Musa sp.). This system was implemented in a house without proper sanitary sewage in the county of João Monlevade, Minas Gerais. The TSE was constructed from three polyethylene barrel arranged in series and positioned below the surface of the land; these received the sewage from the bathrooms of the house. TEVAP was built in a waterproofed ferrocement and filled with substrates, these received TSE (blackwater) and effluent from the kitchen (greywater). Water was removed from the TEVAP through the absorption by the radicular zone of the banana plants and evapotranspiration of the soil-plant system. The treatment system was evaluated for six months. Effluent samples were collected at three different points and submitted to physical-chemical and microbiological analysis. The combined system showed satisfactory removal efficiency for almost all evaluated parameters. The average removal efficiency was found to be 75.55% (BOD), 81.57% (COD), 83.45% (TSS), 92.13% (turbidity), 81.59% (total phosphorus) and 97.21% (thermotolerant coliforms). Ammonia nitrogen was the only parameter that presented low removal potential (27.61%). An increased of DO concentration to 2.0 mg.L-1 was observed. The final pH was in the range of 7,3.