Desempenho de sistemas alagados construídos cultivados com Mentha aquatica no tratamento de esgoto sanitário

• Autor(a) principal: Avelar, Fabiana Ferreira
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/715
• topic: Esgoto; Sistema alagado construído; Mentha aquatica; Sewage; Constructed wetland systems; Mentha aquatica; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA

A process for treating domestic waste water for potential use in small communities is treatment in constructed wetlands (CWs). The Mentha aquatica, called Water Mint, may be useful in the reduction of pollutants in water, especially microorganisms. This study aimed to: evaluate the performance of Mentha aquatica in constructed wetlands of subsurface horizontal flow (CWs-SSHF), with regard to removal of organic matter, nutrients and coliforms in sewage; adjust parameters of bacterial decay kinetic models along the length of CWs-SSHF and determine the yield and major constituents present in the essential oil extracted from Mentha aquatica when grown under different organic loading rates. For this, four CWs-SSHF measuring 24,0m x 1,0m x 0,35m were built and filled with a 0,20 m high layer gravel # 0, as a support medium. Mentha aquatica was planted in two CWs-SSHF (1 and 4), the other two remained without vegetation. The experiment was conducted in two stages: in the first, hydraulic retention times (HRT) of 6,0 and 4,5 days, corresponding to organic loading rate (TCO) of 40,35 kg ha-1 d-1(CW-SSHF 1 and 2) and 53,80 kg ha-1 d-1 (CW-SSHF 3 and 4) were evaluated. These systems were designated SAC-EHSS 1A, EHSS-SAC 2A, SAC-EHSS 3A and SAC-EHSS 4A, respectively. In the second stage, HRT of 3,0 and 1,5 days, corresponding to TCO of 79,66 kg ha-1 d-1 (CW-SSHF 1 and 2) and 160,35 kg ha-1 d-1 (CW-SSHF 3 and 4) were evaluated. These systems were designated SAC-EHSS 1B, EHSS-SAC 2B, SAC-EHSS 3B and SAC-EHSS 4B, respectively. To evaluate systems performance, the following variables were quantified: chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen, phosphorus, potassium, sodium, total coliforms and Escherichia coli. The average removal efficiencies of COD ranged from 71,3 to 91,4% and 75,3 to 91,0% in BOD. With respect to nutrients, average removals ranged from 29,5 to 77,2% N, 12,8 to 58,3% P, 20,4 to 63,3% K and 17,5 to 53,4% Na. Reduction in the total coliforms was 1,29 to 3,41 log units and 1,13 to 3,46 log units in E. coli. Improved efficiencies in removal of nitrogen, total coliforms and E. coli were viii observed at higher HRT. The presence of Mentha aquatica in CW-SSHF increased removal of nutrients, total coliforms and E. coli from sewage. Mathematical models evaluated (Reed, 1995; Laber, 1999; Brasil et al., 2007 e Kadlec e Wallace, 2008) showed good fit to average total coliforms and E. coli reductions, highlighting, among them the model proposed by Brazil et al. (2007). No differences in yield and essential oil composition were observed implanted systems at higher TCO. Limonene, germacrene D and viridiflorol were the main constituents of mint leaves grown in CWs-SSHF.