Capacidade desnitrificante de sistemas alagados construídos operados em bateladas sequenciais

• Ano de defesa: 2011
• Autor(a) principal: Zaparoli, Benatti Rezende
• Orientador(a): Borges, Alisson Carraro
• Banca de defesa: Calijuri, Maria Lúcia , Moreira, Débora Astoni
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Engenharia Agrícola
• Departamento: Construções rurais e ambiência; Energia na agricultura; Mecanização agrícola; Processamento de produ
• País: BR
• Palavras-chave em Português: Wetlands; Taboa; Vetiver; Nitrogênio; Leitos cultivados; Nitrato
• Palavras-chave em Inglês: Wetlands; Cattail; Vetiver; nitrogen; Nitrate
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA
• Link de acesso: http://locus.ufv.br/handle/123456789/3602

Investigations related to the use of constructed wetlands (CWs) for secondary and tertiary treatment has been conducted in Brazilian research centers in the last decade. Regarding the tertiary treatment, it can be considered that removal of nitrogen takes place by a wide range of physical, chemical and biological mechanisms. With the aim of deepening the knowledge on the mechanisms of nitrate removal in water, tried to study the research in question, the phenomenon of denitrification and uptake by plants in CWs. In order to accomplish that, it was applied nitrate as sole nitrogen source, in different CWs were operated in sequencing batch. CWs are not planted and planted with Typha latifolia (cattail) and Chrysopogon zizanioides (vetiver grass) received an average influent concentration of 52.8 g m-3 N-NO3-, and in a total of 6 units, 3 received 10 mL of ethanol as external carbon source. The experiment consisted of different phases, with cycle time (tc) of 3 days (phase I) and 1 day (phase II). There was also a final stage of testing (phase III), in which a study of the decay of values of solute concentration over a tc of 3 days. The results of removal efficiency of nitrate (phase I) were 11.7, 36.7 and 54.8% in the CW control (SACC), grown with cattail (SACT) and planted with vetiver (SACV), respectively. In CWs received external carbon source, the nitrate removal efficiency was 98.0, 99.6 and 99.9% for the SAC control with addition of ethanol (CWC*), grown with cattail with the addition of ethanol (SACT*) and vetiver grown with the addition of ethanol (CWV*), respectively. During Phase II, the removal of nitrate was 3.6, 14.4 and 15.7% in the SACC, SACT and SACV, respectively and 94.7, 95.5 and 97.5% in the SACC*, SACT* and SACV* respectively. With the closure of the activities, there was the cutting of the shoots for analysis of leaf nitrogen, in order to quantify the proportion of nitrogen that was incorporated by the plants. The total of 2.7 and 3.0 g m-2 d-1 N-NO3- removed in phase II, by the SACT and SACV, respectively, only 0.26 and 0.23 g m-2 d-1 were related to their absorption by plants. The highest efficiencies of SACT and SACV, compared to the removal of 0.7 g m-2 d-1 N-NO3- by the SACC, are mainly the carbon source, released by plant roots, thus occurring higher denitrification. In phase II, the highest nitrate removal efficiency due to absorption by plants was 13.3%, obtained in SACT and 10.4% in the SACV and the remainder is attributed to denitrification. Systems that have received external source of carbon removed virtually all the nitrogen applied. During the experiment were also analyzed other important variables for better results of denitrification. They are: chemical oxygen demand (COD), hydrogen potential (pH), oxidation and reduction potential (Eh), alkalinity, nitrite, temperature and evapotranspiration. It was also analyzed the production of biofilm in CWs, the analysis of volatile solids (TVS) and analysis of dry matter production by plants. The systems were effective in removing nitrate, especially in systems planted. Among the systems planted, CWs cultivated with vetiver showed better results in nitrogen removal in terms of a balanced system as well. The addition of ethanol increased the efficiency of denitrification, but should be alert to the increased concentration of nitrite in the CWs.