Eficiência de alagados construídos para o tratamento de águas residuárias com baixas cargas orgânicas

• Autor(a) principal: Queluz, João Gabriel Thomaz [UNESP]
• Data de Publicação: 2016
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/144989
• topic: Constructed wetlands; Domestic wastewater treatment; Hydraulic models; Organic matter; Wetlands construídos; Tratamento de águas residuárias domésticas; Modelos hidráulicos; Typha latifólia; Matéria orgânica

Most wastewater treatment systems are complex, have expensive cost for both construction and maintenance, and require skilled manpower for operation, features that practically precludes its adoption in rural areas of the country. Rural areas require simple and low-cost systems, characteristics found in constructed wetlands. This study aimed 1) to develop a constructed wetland system for wastewater treatment; 2) to assess the constructed wetlands efficiency using different densities of macrophytes; 3) to check the system response to different organic matter application rates; 4) to adjust and modify hydraulic models which represent the kinetics of organic matter and fecal coliforms removal. It was developed a treatment system with three constructed wetlands beds, composed by four rectangular water storage tanks connected in series. The water tanks were filled with gravel (Ø = 2.4 – 9.5 mm) to a height of 30 cm and were saturated with effluent to a height of 25 cm. The constructed wetlands were cultivated with different cattail (Typha latifolia) densities: 0, 11.5 and 23 plants m-2. Each bed received 50 liters of domestic wastewater per day, resulting in 3.2 days of nominal hydraulic retention time. The system efficiency was evaluated by the analysis of fecal coliforms, total coliforms, electrical conductivity, biochemical oxygen demand, chemical oxygen demand, total phosphorus, total nitrogen, pH, potassium, redox potential, total suspended solids, temperature, and turbidity. Linear regression analysis was performed to compare the efficiency of the three constructed wetlands in the removal of organic matter and pathogens. Furthermore, chemical oxygen demand and fecal coliforms data were compared with conventional hydraulic models using the coefficient of determination. The constructed wetlands were efficient for removing fecal coliforms (99%), biochemical oxygen demand (72%), chemical oxygen demand (80%), total nitrogen (73%), total phosphorus (83%), potassium (54%) and suspended solids (98%). The macrophytes density did not affect the efficiency of the three constructed wetlands for removing fecal coliforms and chemical oxygen demand. However, the beds cultivated with macrophytes presented higher efficiency in the removal of nitrogen, phosphorus and potassium. The constructed wetlands responded to the different organic matter application rates, with positive linear correlation between the applied and removed rates. The chemical oxygen demand and fecal coliforms data were compared with the predicted values provided by the conventional hydraulic models (plug flow and tanks in series). The conventional plug flow model was then modified and a degradation resistance factor (q) was included. The modified plug flow model showed better fit to the organic matter data than the conventional hydraulic models (whether or not evapotranspiration was considered: q = 0.521631 and q = 0.479332). On the other hand, the modified plug flow model did not show better fit to the fecal coliforms data than the conventional plug flow models. In conclusion, it is suggested that the modified plug flow hydraulic model should be used for the design and the assessment of organic matter removal efficiency in constructed wetlands.