Modelos de remoção de matéria orgânica e nutrientes de águas residuárias da suinocultura em sistemas alagados construídos

• Autor(a) principal: Fia, Fátima Resende Luiz
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/673
• topic: Constante cinética; Modelagem; Wetlands; Kinetic constant; Modeling; Wetland; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA::ENGENHARIA DE AGUA E SOLO

Although there are various studies in scientific literature in which the potential use of constructed wetland (CWs) on treatment of wastewater, there is no secure indication of project parameters for sizing of CWs, principally those destined for treatment of agroindustrial wastewater. The objective of this study was to evaluate the performance of CWs for treatment of swine wastewater (SWW), with different organic loading rates (OLR), and obtain kinetic parameters for sizing of CWs to be used for treatment of these waters, as well as evaluate the nutrient removal capacity by cultivated plant species. To perform this study, nine tanks were constructed at the Experimental Area of Agricultural Product Storage and Processing, of the Department of Agricultural Engineering, UFV, each measuring 2.0 m x 0.5 m x 0.6 m, built of fiberglass, filled with a 0.55 m layer of crushed stone # zero, and a water level maintained at 0.5 m. CW3, CW5, CW7 and CW9 were planted with Tifton 85 Bermudagrass (Cynodon spp.) and in CW2, CW4, CW6 and CW8 cattail was planted (Typha latifolia). The CW1 was used as control, in which no plant species was cultivated. After one month of experimental implementation, application of the ARS was initiated in the CWs, provided by the Swine Producing Sector of the Animal Science Department of UFV. The corresponding OLR of 163 (CW1, CW2 and CW3), 327 (CW4 and CW5), 460 (CW6 and CW7) and 561 kg ha-1 d-1 of BOD (CW8 and CW9) were applied for the hydraulic retention times (HRT) referring to each OLR, respectively, of 11.9, 5.9, 4.2 and 3.6 days. For evaluation of the pollutant removal efficiencies, 12 samples were taken of the CW influent and effluents, between the months of April and September of 2009, for a system monitoring period of 120 days. Nine of the 12 samples were performed along the CWs, in points spaced at every 0.33 m of length to obtain the coefficients of organic matter degradation and removal of nutrients, which was performed by adjusting first order prediction models (REED et al., 1995), and its variants, as proposed by BRASIL et al. (2007), LABER et al. (1999), COOPER (1999) and KADLEC & WALLACE (2008). At 60 and 120 days after beginning application of ARS and monitoring of the systems, the grasses were cut to evaluate productivity and nutrient levels in the aerial part of the plants. In regards to organic matter removal in the form of BOD, no statistical difference (p<0.05) was verified between the different CWs, being that the average removal efficiencies varied between 75 and 88%. The average COD and TSS varied from 67 to 82% and 84 to 90% and differed among themselves at 5% probability by the Tukey Test for the different OLR (treatments). There was statistical difference between the averages of nitrogen removal in the CWs, where the greatest removals were obtained in those which received the lowest nutrient loads (CW1, CW2 and CW3), varying from 26 to 40% for the different OLR. Increase in the concentrations of nitrate and nitrite was verified along the CWs, proving the nitrification capacity of the medium, although small, in systems that operate under greater OLR. Among the efficiencies measured for removal of phosphorus, significant difference (p<0.05) was verified between the different treatments, varying between 65 and 78%, values that can be considered satisfactory. Cattail did not adapt to the loading conditions imposed on the CWs, producing a reduced quantity of dry material (0.75 to 1.76 Mg ha-1) and presenting complete senescence in CW6 and CW8 which received the greatest OLR. Tifton 85 Bermudagrass presented good development and greater productivity of dry material (4.73 to 6.26 Mg ha-1), standing out in relation to cattail for nutrient removal, except for sodium. Despite cattail presenting a greater concentration of nutrients in leaf tissue (except nitrogen and phosphorus), which can be attributed to the lower dilution in the produced biomass, the biomass production capacity was the factor responsible for the greater removal percentages presented by the Tifton 85 Bermudagrass. In relation to adjustment of kinetic models, it was verified that the first order model and that proposed by LABER et al. (1999) and COOPER (1999) did not adjust well to the data obtained in this study, while the models of BRASIL et al. (2007) and KADLEC & WALLACE (2008) were more suitable and precisely described kinetics for removal of organic matter (BOD and COD) and nutrients (TKN and P) in the evaluated systems, generally presenting R2 greater than 90%.