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Constructd wetland system is one of the ecological engineering technologies used on wastewater treatments. In this study, we discussed the treatment efficiencies of oil refining and steel-milling wastewater by four lab-scale constructed wetland systems (0.8-m long by 0.4-m wide by 0.7-m deep), which were all filled with gravel media, and planted with Phragmites communis. The constructed wetland systems were designed into two types: free water surface (FWS) and subsurface flow (SSF) wetland systems, which were discharged with two different types of wastewater (oil refining and steel-milling). The experiments of this study were run by five stages. The experimental results showed that almost all of the contaminants could be reliably removed from wastewater by the constructed wetland systems, especially in the SSF systems. During the experiments, the second stage of the experiments had the best treatment efficiencies, in which the flowrate was controlled at 5mL/min. The hydraulic retention time (HRT) in FWS and in SSF werecalculated equal to 7.5days, and 5.36days, respectively.

In recent years, interest in wastewater treatment through constructed wetlands has been significantly increased because of their low cost and energy requirement. In this study, pilot-scale constructed wetland systems were developed to evaluate the efficacy and effectiveness on the treatment of oil-refining and steel-milling wastewater. The constructed wetland used to treat the oil-refining wastewater included one free water surface system (FWS) filled with sandy media and one subsurface flow system filled with gravel media. The plants grown on the wetland were Phragmites communis. The hydraulic retention time for the two systems was approximately 7 and 5 days, respectively. A two-stage subsurface flow constructed wetland system was used to treat steel-milling wastewater. This system, which filled with gravel media were planted with Phragmites communis (the first stage) and Typha orientalis (the second stage). The hydraulic retention time for this system was approximately 7 days. Experimental results showed that the two constructed wetland systems for the oil-refining wastewater treatment could remove most of the wastewater pollutants. Moreover, the first system (FWS) played a more important role on the wastewater treatment. The efficiency of the first stage of the wetland system, which was used for steel-milling wastewater treatment was not significant due to the inhibition of the plant growth by the wastewater. However, the treatment efficiency was increased at the second stage after planting new plants. Results from the two-stage treatment system indicate that higher treatment efficiencies were observed except for ammonium. Results from this study would be very useful in the design of constructed wetlands for practical application to treat oil-refining and steel-milling wastewaters.

Made available in DSpace on 2015-03-26T13:23:42Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2319739 bytes, checksum: 8d787f013c376eae45142c8b694720cf (MD5) Previous issue date: 2012-02-16 / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Constructed wetland systems of horizontal subsurface flow (CW-SSHF) are systems used in wastewater treatment. The objective of the present study was to assess possible changes in hydrodynamic conditions, through analysis of hydraulic conductivity and forms of nitrogen in CW-SSHF. In this study, six CW-SSHF were installed with dimensions of 0.6 m x 0.5 m x 2.0 m in height, width and length, respectively, with no bottom slope, filled with pea gravel and maintained in a greenhouse for the treatment of swine wastewater (ARS). CW-SSHF1 and CW-SSHF4 were not cultivated with any plant species (control), while CW-SSHF2 and CW-SSHF5 were planted with Tifton 85 (Cynodon spp.), and CW-SSHF3 and CW-SSHF6 were planted with Alligator weed (Alternanthera philoxeroides). During the experimental period six samples were collected of the influent (ARSA) and effluent (ARSE) of each CW-SSHF. Five hydraulic conductivity tests were also conducted along the length of the systems as a function of time, in order to evaluate the effects of vegetation, position and time on this variable. For comparison, hydraulic conductivity was determined in one CW-SSHF filled with pea gravel and submitted to flow of clean water. In all CW-SSHF an average organic loading rate of 411 kg ha-1 d-1 was applied with average flow of 0.069 m3 d-1, where the hydraulic retention time was equal to 3.6 d. The monitoring period was 63 days. At the end of the experiment, the plants were cut and the dry material yield was determined. The analysis of variance of hydraulic conductivity showed that only the interaction of position and vegetation effects was significant at the level of 10% probability. Hydraulic conductivity values in the thirds ranged from 1,392 m d-1 to 2,834 m d-1, where the differences between thirds of the CW-SSHF primarily occurred between the planted and non-planted systems by the Tukey test level 10% probability. All CW-SSHF presented average hydraulic conductivity values less than those obtained the system with clean water, which was 2680 m d-1. Dry matter yields in the different thirds of the bed ranged from 6.0 to 9.8 t ha-1 in the CW-SSHF planted with Tifton 85 and Alligator weed during the growth period of 60 days. The removal efficiency of total nitrogen (NT) and ammonium (N-NH4+) was considered low, ranging from 8 to 15% and 3 to 13%, respectively. Nitrate (N-NO3-) removal efficiency ranged from 45 to 53%. In all cases, the cultivated CW-SSHF showed higher efficiency for nitrogen removal. The CW-SSHF did not provide conditions which favored the occurrence of nitrification/denitrification. / Os sistemas alagados construídos de escoamento horizontal subsuperficial (SACs-EHSS) são sistemas utilizados no tratamento de águas residuárias. Com a realização deste estudo, objetivou-se avaliar possíveis alterações nas condições hidrodinâmicas, via análise da condutividade hidráulica, e nas formas do nitrogênio em SACs-EHSS. Para possibilitar este estudo, foram instalados seis SACs-EHSS, nas dimensões de 0,6 m x 0,5 m x 2,0 m de altura, largura e comprimento, respectivamente, sem declividade de fundo, preenchidos com brita zero e mantidos em casa de vegetação, para se efetuar o tratamento de água residuária de suinocultura (ARS). Os SAC-EHSS1 e SAC-EHSS4 não foram cultivados com qualquer espécie vegetal (controle), os SAC-EHSS2 e SAC-EHSS5 foram cultivados com capim tifton 85 (Cynodon spp.) e os SAC-EHSS-EHSS3 e SAC-EHSS6 cultivados com alternanthera (Alternanthera philoxeroides). Durante o período experimental foram coletadas seis amostras do afluente (ARSA) e do efluente (ARSE) de cada SAC-EHSS. Realizaram-se, também, cinco testes de condutividade hidráulica, ao longo do sistema e ao longo do tempo, a fim de se avaliar os efeitos da vegetação, posição e tempo sobre esta variável. A título de comparação, determinou-se a condutividade hidráulica em um SACs-EHSS preenchido com brita e submetido a escoamento de água limpa. Em todos os SACs-EHSS foi aplicada, em média, uma taxa de carregamento orgânico de 411 kg ha-1 d-1 e vazão média de 0,069 m3 d-1, sendo o tempo de detenção hidráulica igual a 3,6 d. O período de monitoramento foi de 63 dias. Ao final do experimento, foi feito um corte das plantas e determinada a produtividade de matéria seca. A análise de variância dos dados de condutividade hidráulica demonstrou que apenas a interação dos efeitos posição e vegetação foi significativa, em nível de 10 % de probabilidade. Os valores de condutividade hidráulica para os terços variaram de 1.392 m d-1 a 2.834 m d-1, sendo que as diferenças entre os terços dos SACs-EHSS ocorreram, basicamente, entre os vegetados e não vegetados, pelo teste Tukey, em nível de 10% de probabilidade. Todos os SACs-EHSS apresentaram condutividade hidráulica média inferior à obtida na brita limpa, que foi de 2.680 m d-1. A produtividade de matéria seca nos terços do leito variou de 6,0 a 9,8 t ha-1, nos SACs-EHSS cultivados com tifton 85 e alternanthera, em um período de 60 dias de cultivo. A eficiência na remoção de nitrogênio total (NT) e amônio (N-NH4+) foram consideradas baixas, variando de 8 a 15% e 3 a 13%, respectivamente. A eficiência de remoção de nitrato (N-NO3-) variou de 45 a 53%. Em todos os casos, os SACs-EHSS cultivados apresentaram maior eficiência na remoção de nitrogênio. Os SACs-EHSS não proporcionaram condições que favorecessem a ocorrência de nitrificação/desnitrificação.

A mechanistic understanding of transport and degradation processes of modern agricultural pesticides, including chiral pesticides, is critical for predicting their fate in the environment. In agricultural landscapes, wetlands can intercept pesticide-contaminated runoff or groundwater and improve water quality through various retention and degradation processes, which remain unknown. In a downscaling approach, three different wetlands receiving agricultural runoff were used as 'natural laboratories' to investigate the fate of widely used pesticides. Overall, our results showed that dynamics of hydrological and redox conditions largely influenced pesticide sorption mechanisms and their distribution over time within wetland compartments, thereby controlling degradation processes. While large-scale studies provide integrative information on pesticide dissipation and distribution patterns with respect to wetland functioning, small-scale investigations using novel methods such as isotope and enantiomer analyses characterize underlying molecular processes governing pesticide degradation.

La compréhension des mécanismes de transport et de dégradation des pesticides émergents est primordiale pour prédire leur devenir dans l’environnement. Les zones humides peuvent intercepter des eaux de ruissellement ou des souterraines contaminées par les pesticides et les traiter par le biais de processus de rétention et de dégradation, encore peu connus. Dans une approche multi-échelles, trois zones humides recevant des eaux polluées par les pesticides ont été utilisées comme des « laboratoires naturels » pour étudier le devenir de pesticides couramment utilisés. Cette thèse souligne l’influence des conditions hydrologiques et redox sur la distribution des pesticides au sein des différents compartiments des zones humides ainsi que sur leur potentiel de dégradation. Alors que les études à grande échelle fournissent des informations intégratives sur la dissipation et la rétention des pesticides en lien avec le développement de la végétation, les études à petite échelle utilisant des techniques innovantes telles que les analyses isotopiques et énantiomériques permettent l’exploration des processus moléculaires de dégradation des pesticides. / A mechanistic understanding of transport and degradation processes of modern agricultural pesticides, including chiral pesticides, is critical for predicting their fate in the environment. In agricultural landscapes, wetlands can intercept pesticide-contaminated runoff or groundwater and improve water quality through various retention and degradation processes, which remain unknown. In a downscaling approach, three different wetlands receiving agricultural runoff were used as ‘natural laboratories’ to investigate the fate of widely used pesticides. Overall, our results showed that dynamics of hydrological and redox conditions largely influenced pesticide sorption mechanisms and their distribution over time within wetland compartments, thereby controlling degradation processes. While large-scale studies provide integrative information on pesticide dissipation and distribution patterns with respect to wetland functioning, small-scale investigations using novel methods such as isotope and enantiomer analyses characterize underlying molecular processes governing pesticide degradation.