Tratamento de efluentes domésticos em um wetland construído de fluxo vertical com fundo saturado

• Autor(a) principal: Baggiotto, Carine
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Manancial - Repositório Digital da UFSM
• Texto Completo: http://repositorio.ufsm.br/handle/1/26277
• topic: Tratamento descentralizado; Comunidade bacteriana; Nitrificação; Desnitrificação; Saturação parcial; Efluente doméstico; Decentralized treatment; Bacterial community; Nitrification; Denitrification; Partial saturation; Domestic effluent; CNPQ::ENGENHARIAS::ENGENHARIA CIVIL

The objective of this work was to evaluate the influence in saturation on the nitrogen removal performance of vertical flow constructed wetlands (VFCW), filled with gravel, in the post-treatment of anaerobic septic tank effluent (ST). The research was designed based on two experimental systems: a benchtop and a full-scale one. In the first experiment, 200 mm diameter PVC pipes were used, filled with gravel. Canna x generalis seedlings were transplanted into them, fed with the TS effluent 5 times a day, for 3.5 days a week, with the same time for resting. Three hydraulic loading rates - HLR (40, 70 and 100 mm.d-1) were tested for two saturation conditions: 20% (15 cm) and 33% (25 cm). Qualitative and quantitative monitoring of influent and effluent wastewater from each treatment unit was carried out, evaluating the following parameters: chemical oxygen demand (CODt), total Kjeldahl nitrogen (TKN), ammonia nitrogen (N-NH4+), nitrite (N -NO2-) and nitrate (N-NO3-), alkalinity, solids series and pH. In the second experiment, these same parameters were analyzed in a full-scale system composed of TS (V=4.7 m3) and WCFV (A = 24.5 m2, filled with gravel and planted with Canna x generalis), in order to compare the effect of saturation (phase II) compared to the previous phase, with recirculation of the treated effluent in the VFCW to the septic tank (phase I). Furthermore, 16S rRNA sequencing was used to identify the nitrifying and denitrifying bacterial community present in the system through samples of the support medium (gravel) at different points of the VFCW. In the benchtop system, the results showed that the saturation height that best removed NT was 25 cm. In the full-scale experiment, with 25 cm of saturation, efficiencies of 61%, 63%, 91%, 40%, 92% and 88% were found for the VFCW for N-NH4+, TN, TSS, TS, BOD and CODt, respectively. When statistically analyzing the effluent concentrations and the global efficiencies of the different operational phases, it was noticed that COD and NT did not present a significant difference. Microbiological analysis in the wetland bed showed the presence of Chromatiales, Xanthomonadales, Nitrospirales families on the surface and in the middle of the wetland bed, both in summer and in winter. At the bottom of the wetland, in the saturation layer, Rhodocyclales and Nitrospiraceae were also observed in winter and summer. The analysis also determined that there was low diversity of nitrifying and denitrifying bacteria. Nitrospira family genera predominated as nitrifying bacteria and Rhodocyclaceae and Bradyrhizobiaceae family genera predominated as denitrifying bacteria. Operation with a saturated bottom offers advantages over recirculation, mainly related to lower energy consumption (for pumping) and greater operational simplicity.