Hidrodinâmica e desempenho de filtros verticais com alimentação em pulso, plantados e não plantados, empregados no tratamento de esgoto sanitário bruto

Abstract

Vertical Planted Filter, a type of constructed wetland, has been studied worldwide for the treatment of different types of wastewater, including raw sewage. Among the different types of FVP, the Constructed Wetland System Intermittent Downflow (or Pulse Loaded), stands out. In this thesis, the Portuguese name Filtro Vertical Plantado descendente e alimentação em pulso (FVP-AP) for this type of filter has been adopted. This research is about a variant of FVP-AP, also called the French System, and has as its primary focus the evaluation of the hydraulic behavior of its 1 st stage, consisting of three filters fed in parallel, with alternating phases of feeding and rest. The experiment, consisting of the 1 st stage of the French System and was implanted in the Centre for Research and Training in Sanitation UFMG / COPASA (CePTs), located in the sub-basin Arrudas in Belo Horizonte / MG, Brazil. The first filter was originally planted with the species Typha latifolia (cattail) and subsequently replaced by Tifton-85. The second filter was planted with Tifton-85 (Cynodon dactylon Pers.) and the third was not planted, acting as a control. The design flow was equal to 12 m³.d -1 (1 m 2 /inhab), corresponding to Hydraulic Load Rate (HLR) equal 0.4 m 3 .m -2 .d. For the same HLR, two dosing regime were tested: (i) higher frequency: application of 24 batches of 530 litres per day; (ii) lower frequency: application of 12 batches of 940 litres per day. The tests were conducted first on new filters, before they had received any previous applications of sewage. Tests were also conducted after 11 months of operation. The dosing regime, the period of filter usage and the presence of plants all had an impact on the system’s hydraulic retention time. In general, there was a strong axial dispersion in the planted and unplanted filter, for all tested conditions. Great dispersion in the units and the presence of short-circuiting and dead zones were also detected. Regarding the removal of pollutants, the best performance was observed in the planted filter Tifton-85, confirming the important role of vegetation in removing pollutants. Mean removal efficiencies were very good in this filter: 94, 81, 81 and 60% for TSS, BOD, COD and TKN, respectively, indicating the high potential of this technology for small Brazilian communities.