In Brazil, there is a deficit of access in relation to sewage services for a large part of the population, and this fact is the one responsible for the contamination of watercourses. This is because to the lack of investment in infrastructure in the country, since sewage treatment plants require high costs and high area demand for deployment, besides the installation of the collection system, which
directs the wastewater to treatment. This paper describes the behavior of wetlands as a post treatment step for anaerobically treated sewage in order to the removal of organic matter, suspended solids, nitrogen compounds, total phosphorus and faecal coliforms. Raw sewage was treated in a Upflow Anaerobic Sludge Blanket (UASB) reactor with a retention time of 8 h and the effluent was
used in two biosystems of constructed wetlands (CWs), vertical flow and horizontal flow, operated in series, with crushed stone of different diameters and continuous flow. The UASB reactor with post-treatment with CWs has achieved high overall removal efficiencies for chemical oxygen demand (COD), total suspended solids (TSS) and faecal coliforms: 96.5%, 98.4% and 98.2%, respectively. In relation to total Kjeldahl nitrogen (TKN), ammonia and phosphorus the results were similar to those described in the literature, with mean values of 67.1%, 63.4% and 63.5, respectively. The anaerobic pretreatment reduced the area of the CW by about 60%, and appeared to be helpful to prevent CW clogging and odor problems.