• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 605
  • 168
  • 52
  • 37
  • 36
  • 15
  • 14
  • 13
  • 9
  • 9
  • 9
  • 9
  • 9
  • 9
  • 7
  • Tagged with
  • 1163
  • 246
  • 229
  • 184
  • 177
  • 172
  • 123
  • 108
  • 74
  • 71
  • 69
  • 68
  • 67
  • 65
  • 62
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
491

[en] ECOLOGICAL TREATMENT OF DOMESTIC EFFLUENTS WITH USE OF WETLANDS / [pt] TRATAMENTO ECOLÓGICO DE EFLUENTES DOMÉSTICOS COM O USO DE WETLANDS

ADRIANA FAVACHO CURTY 05 February 2019 (has links)
[pt] A presente dissertação trata da análise do tratamento de efluentes de esgotos domésticos, processado na ETE Ponte dos Leites, município de Araruama, Rio de Janeiro, que se destaca-se por seu enfoque ecológico. A escolha dessa ETE se deu por ser exemplo brasileiro de utilização de recursos naturais na purificação de esgotos, os wetlands construídos, nos quais as macrófitas absorvem nitrogênio e fósforo do efluente, elementos que constituem sua fonte de nutrição. Tal tratamento imita o ciclo natural, recuperando flora e fauna, preservando o meio ambiente. Os resultados da pesquisa a qual foi baseada no exemplo que ilustra esta pesquisa e que permitiram listar vantagens e desvantagens. As primeiras reúnem aspectos econômicos, sociais e ambientais enquanto que as desvantagens se referem à ausência de conhecimento acerca da comercialização do reúso do efluente tratado, da disponibilidade de áreas, da necessidade de manejo frequente para não comprometer os resultados e evitar a contínua geração de resíduos sólidos de origem vegetal. A pesquisa de campo sublinhou que a implantação de plantas no processo contribui economicamente e promove resiliência do ambiente. Pode-se concluir que é a tecnologia mais adequada a fim de reaproveitar todo resíduo sólido gerado e favorecer o reúso da água, pois permite a possibilidade de preservação da água desde que o reúso seja empregado para fins que não envolvam o consumo humano. / [en] The biggest problem of cities, as they reach the 21st century, is to meet the basic needs of their inhabitants. Population growth increasingly requires areas for housing and food production, and a site devoted to the waste generated by this population. With multiplication, the need for natural resources increases. The most discussed subject in this century is the water crisis. Added to the disastrous consequences that have led to the lack of appeal. The question of water needs to be rethought in relation to traditional management. That is, the capture and availability still come using molds from the beginning of the last century, which have contributed to increase environmental and financial losses, and above all contribute to poor quality of life. What this research intends to emphasize is the urgency of a change in the concept of treatment of domestic sewage, in order to reach the reuse of the treated effluent, which is the reuse. The hypothesis that it brings is to point out as a possible solution - constructed wetlands. The constructed wetlands is a type of sewage treatment that allows the reuse of water. The technology is simple, easy to maintain and economically favorable. The environmental advantages are representative with added social aspects. Household effluents are treated by plants known as: macrophytes, these mimic the cycles of nature, are the most appropriate for the purification process, do not use chemicals, nor anthropize areas for the implantation of the treatment plant, and waste generated are totally reused. The research focuses on the applicability of constructed wetlands, exemplifying architectural and urban design, which served to recover degraded urban areas, restoring natural life. The most relevant point is the resilience of the natural urban environment, of areas that have been degraded. The wetlands favor thermal equilibrium, which evidently represents the life value of the planet s species.
492

Diatoms and invertebrates as indicators of pH in wetlands of the south-west of Western Australia

Thomas, Erin J January 2007 (has links)
Increased groundwater usage, rainfall decline and activities such as mining have resulted in the acidification of certain wetlands in the south-west of Western Australia. This study investigated the influence of pH, the factor most commonly associated with acidification, on the invertebrate and diatom community structure of 20 wetlands in the south-west region of Western Australia. Few studies in Western Australia have investigated both biotic groups, particularly in relation to pH. Consequently, this study examined the comparative sensitivity of the two biotic groups to pH in order to identify the most effective biotic tool for assessing the ecological impacts of pH decrease. The wetlands included in this study displayed a wide range of pH from acidic (pH < 6.5) to alkaline (pH > 7.5). Other environmental parameters were also variable. Separation of the wetlands into three pH groups; Group 1 – acidic, Group 2 – circumneutral and Group 3 – alkaline, demonstrated that the acidic Group 1 wetlands generally had higher electrical conductivity than the remaining groups. This was probably due to the association of many Group 1 sites with mining and acid sulphate soils. Seasonal trends in environmental variables across the three pH groups were mostly unclear although some trends were evident within the individual pH groups. The study showed that invertebrate community structure differed in response to pH. However, the results also demonstrated that invertebrate distribution patterns were influenced by other factors. / Potential indicator species identified from the study included Macrothrix indistincta and Tanytarsus fuscithorax/semibarbitarsus which were abundant in acidic waters and Alona quadrangularis which was common in circumneutral sites. Taxa such as Calamoecia tasmanica subattenuata were common over a wider range of pH (acidic to circumneutral) but may still have potential to act as indicators of pH decline. Diatom community structure was also shown to be influenced by pH, with the variable identified as a major determinant of diatom distribution patterns. Nitzschia paleaeformis and Navicula aff. cari were generally recorded from acidic wetlands and are potentially useful as indicators of low pH conditions. Brachysira brebissonii and Frustulia magaliesmontana were also identified as species with the potential to indicate pH decline. In contrast, taxa including Gomphonema parvulum, Staurosira construens var. venter and Nitzschia palea were generally associated with moderate to high pH levels. A comparative study of the two biotic groups using multivariate analyses revealed that diatoms were more sensitive to pH than invertebrates. Further investigation with a larger number of environmental variables would be necessary to ascertain the other factors primarily influencing invertebrate community structure. Nonetheless, the findings imply that diatoms and invertebrates differ in their responsiveness to various environmental factors and may provide complementary information on the integrity of a system. Multivariate analyses on an expanded data-set of 40 sites found that pH accounted for the greatest amount of variation in the data and was conducive to the development of a diatom-based pH inference model. / The strongest model was produced using weighted averaging (WA) with classical deshrinking. While the model displayed a high correlation coefficient, the prediction error was also relatively high, probably as a result of the comparatively small and heterogeneous data-set. Incorporation of the data into a larger training set would be likely to improve the predictive ability. Applications for the model include pH reconstructions or use in monitoring programs. The current study has shown that pH is an important variable influencing both invertebrate and diatom community structure in wetlands in the south-west of Western Australia. However, the greater sensitivity of diatoms to pH suggests that they would be the most effective tool for the biological monitoring of pH in wetlands threatened or impacted by acidification. An integrated monitoring program including both diatoms and invertebrates may provide additional information on the impacts of pH decline and the overall integrity of the systems and should be investigated further.
493

Nitrifying and denitrifying bacterial communities in the sediment and rhizosphere of a free water surface constructed wetland

Ruiz Rueda, Olaya 27 June 2008 (has links)
La contínua descàrrega de nutrients, sobretot fosfats i nitrogen, és la major causa d'eutrofització dels ecosistemes aquàtics. Els sistemes de tractament basats en aiguamolls construïts s'han emprat per reduir ells nivells de nitrogen a l'aigua com a alternativa de baix cost als mètodes de depuració convencionals. L'eliminació del nitrogen a aquests sistemes depèn en bona part de la vegetació, i l'alternança de condicions aeròbiques i anaeròbiques per promoure els processos de nitrificació i desnitrificació. En aquest treball hem volgut investigar les activitats microbianes de nitrificació i desnitrificació en relació a dues espècies de plantes macròfites en un sistema d'aiguamolls de tractament de flux superficial (FS-SAC), dissenyat per minimitzar l'impacte de l'alliberament d'aigua carregada de nutrients a la reserva natural dels Aiguamolls de l'Empordà (Girona, Espanya). / The continuous delivery of nutrients, mainly phosphate and nitrogen, is the major cause of eutrophication of aquatic environments. Treatment technologies based on constructed wetlands have been applied to reduce the levels of nitrogen as a cost-effective alternative compared to conventional treatment methods. The nitrogen removal efficiency in wetlands relies on the presence of plants and the alternation of aerobic and anaerobic conditions to promote both nitrification and denitrification. Although the role of emergent macrophytes in such systems is largely recognized, their contribution to the overall treatment process has not been quantified very frequently. We have investigated the microbial nitrification and denitrification activities in relation to two plant species in a free water surface constructed wetland (FWS-CW), designed to minimize the impact of nutrient release into the Natural Reserve of Els Aiguamolls de l'Empordà (Girona, Spain).
494

Created wetlands in Shing Mun River, Sha Tin

練偉東, Lin, Wai-tung. January 1999 (has links)
published_or_final_version / Architecture / Master / Master of Landscape Architecture
495

Techniques for assessing the impacts of wetlands on hydrological responses under varying climatic conditions.

Gray, Ryan Paul. January 2011 (has links)
Wetlands are considered sensitive eco-tones that provide numerous goods and services, not only to the communities which are immediately dependent upon them, but also to the many downstream stakeholders who benefit from the hydrological influences that wetlands have on a catchment. The three main objectives of this study, the foci of which included an assessment of impacts of wetlands on catchment hydrological responses (viz. flood attenuation and streamflow regulation) in the Thukela catchment under varying geographical and climatic conditions, are: · A modification and validation of the ACRU Model’s Wetland Routine; · Assessing impacts of wetlands on hydrological responses from catchments in varying climatic regions under historical climatic conditions; and · Assessing impacts of wetlands on catchment hydrological responses for climate change scenarios by using outputs from a Regional Climate Model (RCM). The ACRU Model was selected to undertake the daily hydrological simulations, while historical climate data and climate information derived from the C-CAM Regional Climate Model were used as inputs into the model. These varying climatic inputs, as well as the changes in water fluxes between simulations with and without the wetlands routine switched on, enabled the author to assess the impacts of wetlands on catchment hydrological responses under varying climatic conditions. The ACRU wetland routine initially did not produce output in line with conceptualisation of wetlands processes. As a result of this, certain modifications had to be made to the model to ensure that the results obtained mimicked wetlands hydrological processes realistically. A validation was performed on the re-configured ACRU wetlands routine to show that the simulated results of impacts of wetlands on catchment hydrological responses were realistic when compared to findings from the literature review (e.g. in regard to streamflow regulation and flood attenuation). These validation results also show that the impacts of wetlands on catchment hydrological responses are dependent on the level of soil water saturation of the wetland at the start of a streamflow event and the volume of the streamflow event in relation to the relative size of the wetland. The results further illustrate that wetlands have a relatively small flood attenuation and streamflow regulation impact on mean annual catchment hydrology at the outlet of the 29 136 km2 Thukela catchment. However, mean monthly results show pronounced effects (20 – 30%) of flood attenuation in the summer months and streamflow regulation throughout the year, especially in the drier winter months. The climate change scenario results illustrate that the impact of wetlands on hydrological responses are virtually entirely masked by the impact of climate change, with only minor changes shown on outflows of the Thukela between climate change scenarios without and with wetlands. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
496

The utilisation of the WET-Health and WET-EcoServices tools in the application of Wetland decision making.

Ramburran, Esmeralda. 15 November 2013 (has links)
Wetlands serve many purposes in the landscape and are under increasing threat as a consequence of urbanisation despite their importance directly and indirectly to humans. Through an evaluation of the suitability of the WET-Health and WET-EcoServices tools in determining wetland functionality and the provision of goods and services of the wetlands, it was decided that these tools were particularly appropriate for fulfilling the purpose of this research. WET-Health, used in combination with WET-EcoServices, is effective in determining the overall health of wetlands and provides possible reasons for degradation which reduces the ability of wetlands to supply the benefits associated with the particular hydrogeomorphic type. A feedback and questionnaire survey was conducted with eThekwini municipality to determine if the WET-Health and WET-EcoServices tools satisfied their needs and to ascertain whether these tools would be suitable for management of their wetlands. This research, in collaboration with eThekwini municipality’s Planning Department, seeks to contribute to the management and maintenance of wetlands within the uMdloti Catchment so that more informed wetland management decisions regarding wetland sustainability can be made. A level 1 and 2 WET-Health and WET-EcoServices assessments were applied to three sites namely; the Robert Armstrong, Le Mercy and Lake Victoria Barn swallow roosting wetlands. A WET-Health Level 1 assessment can be considered more feasible than a Level 2 which provides similar results yet is more time consuming, however, expert knowledge and experience with the tool may be necessary. A Level 2 WET-EcoServices assessment is recommended as it not only highlights what benefits are being provided but the extent of each benefit thereof also determining whether a wetland has a greater chance to provide a particular benefit but may not being effective in doing so. This in turn allows for efforts and resources to be directed towards improving wetland management and land-use planning and decision making for which the tools are particularly suitable. The tools were considered appropriate and necessary for wetland management and can be adapted into eThekwini municipality’s work situation. The tools provide a holistic approach for wetland assessment as catchment activities are considered. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
497

Key Influences on Hydraulic Efficiency in Treatment Wetlands

Wahl, Mark D. January 2013 (has links)
No description available.
498

Avaliação do ciclo de vida ambiental e econômica de sistemas descentralizados de tratamento de esgoto envolvendo wetlands construídos / Environmental and economic life cycle assessment of wastewater treatment systems involving constructed wetlands

Resende, Juliana Dalia 01 November 2018 (has links)
Os sistemas de tratamento de esgotos, apesar de possibilitarem a eliminação ou redução de poluentes e substâncias indesejados presentes nas águas residuárias, também ocasionam impactos ambientais. Essa característica deve ser levada em consideração no momento da instalação de uma alternativa tecnológica para o tratamento de esgoto e na proposição de melhorias aos sistemas selecionados. Uma das ferramentas que pode ser utilizada para avaliar o desempenho ambiental de sistemas de tratamento de esgoto é a Avaliação do Ciclo de Vida (ACV), a qual pode ser complementada pela metodologia de Avaliação do Custo do Ciclo de Vida (ACCV), que permite calcular o custo total de um projeto ao longo de seu ciclo de vida. No presente estudo, a ACV e a ACCV foram utilizadas com o objetivo de analisar os potenciais impactos ambientais e custos de diferentes configurações de sistemas pilotos de tratamento de esgoto envolvendo wetlands construídos (WC) com e sem aeração. Foram obtidos também fatores de alocação para as potenciais cargas ambientais do lodo e do efluente do tanque séptico, que possibilitarão a realização de estudos futuros de ACV para alternativas de destinação do lodo de tanques sépticos. A modelagem dos sistemas e os cálculos envolvidos na avaliação dos impactos do ciclo de vida foram realizados mediante o uso do software openLCA v. 1.6.3. Para a avaliação das categorias de impacto de acidificação terrestre, mudança climática, eutrofização aquática de água doce, formação de oxidantes fotoquímicos, ecotoxicidade de água doce e toxicidade humana foi utilizado o método de avaliação de impacto ReCiPe. Foram avaliadas também as categorias de ecotoxicidade e toxicidade humana, utilizando o método USEtox. Nas análises envolvendo um WC aerado a etapa de operação se mostrou com um maior potencial de causar impactos ambientais para todas as categorias de impacto analisadas, com resultados variando entre 63,9% para a categoria de toxicidade humana e 99,8% para a categoria de eutrofização de água doce. Na comparação de materiais utilizados na construção dos sistemas, o potencial de causar impactos ambientais da fibra de vidro foi até 4,7 vezes menor que o potencial de causar impactos ambientais da alvenaria em tijolos para todas as categorias de impacto analisadas. Contudo, a utilização de fibra de vidro ao invés de alvenaria em tijolos apresentou custos mais elevados. O custo do ciclo de vida por m3 de esgoto tratado do sistema envolvendo um WC com aeração mostrou-se cerca de 1,8 vezes menor do que o do sistema sem aeração. Os resultados encontrados trazem contribuições que podem auxiliar na tomada de decisão no que diz respeito à implantação e operação de sistemas de tratamento de esgoto, visando tornar estes mais sustentáveis do ponto de vista econômico e ambiental / Although wastewater treatment systems, allow for the elimination or reduction of pollutants and unwanted substances in wastewater, they also cause environmental impacts. One tool that can evaluate the environmental performance of wastewater treatment systems is Life Cycle Assessment (LCA), which can be complemented by Life Cycle Cost Analysis (LCCA), which calculates the total cost of a project over its entire life cycle. In the present study, the LCA and LCCA were used to analyze the potential environmental impacts and costs of different wastewater treatment pilot plant configurations involving constructed wetlands (CW) with and without aeration. The modeling of the systems and the calculations involved in the assessment of the life cycle impacts were performed using the openLCA v. 1.6.3 software. The impact assessment method used for the impact categories of terrestrial acidification, climate change, freshwater aquatic eutrophication, formation of photochemical oxidants, ecotoxicity and human toxicity was ReCiPe. The categories of ecotoxicity and human toxicity were also evaluated using the USEtox method. In the analyzes involving an aerated CW, the operation stage showed the greatest potential to cause environmental impacts for all impact categories analyzed, with results varying between 63.9% for the category of human toxicity and 99.8% for the category of freshwater eutrophication. The comparison of materials used in the construction of systems has demonstrated that the potential to cause environmental impacts of fiberglass was up to 4.7 times less than the potential to cause environmental impacts of brick masonry for all impact categories analyzed. However, the use of fiberglass instead of masonry in bricks has presented higher costs. The life cycle cost per cubic meter of treated sewage of the system involving a CW with aeration was about 1.8 times smaller than that of the system without aeration. Results can aid in decision making regarding the implementation and operation of wastewater treatment plants, in order to make these systems more sustainable from an economic and environmental point of views
499

Estratégias de tratamento de lixiviado de aterro sanitário com foco na matéria orgânica biodegradável e nitrogênio amoniacal / Strategies of landfill leachate treatment focused on biodegradable organic matter and ammonia nitrogen

Cano, Vitor 03 September 2014 (has links)
Introdução sistemas de tratamento de esgotos, quando aplicados ao tratamento de lixiviado de aterro sanitário, não têm apresentado bons resultados. Por conta disso, faz-se necessário o desenvolvimento de alternativas para o tratamento de lixiviado. Objetivo avaliar o pós-tratamento de lixiviado de aterro sanitário por wetland construído de fluxo subsuperficial horizontal e reator biológico de leito móvel (RBLM). Materiais e métodos foram realizados dois experimentos com tratamento de lixiviado após remoção de amônia por dessorção. No experimento 1 utilizou-se wetlands construídos de fluxo horizontal em escala de bancada (volume total de 30,8 L), plantados com Cyperus papyrus, Heliconia psittacorum e Gynerium sagittatum, e um controle sem vegetação, preenchidos com pedrisco calcário. O sistema foi alimentado com lixiviado diluído em água em diferentes proporções (entre 10 por cento e 30 por cento ) com concentração média de DQO entre 336 e 750 mg.L-1 e nitrogênio amoniacal (N-NH4) entre 47 e 199 mg.L-1. A operação ocorreu em três etapas: (1ª) alimentação contínua e TDH médio entre 2,7 e 5,3 d; (2ª) regime de ciclos de recirculação do efluente, para avaliar o efeito do aumento de TDH para 21 dias; (3ª) alimentação contínua de duas unidades wetlands em série, visando elevar o TDH (entre 8,1 e 9,9 d) sem recirculação. O experimento 2 foi implantado em escala piloto, com uma unidade de dessorção de amônia seguida de um Reator Biológico de Leito Móvel (RBLM) e um biofiltro anóxico. O RBLM (volume efetivo de 380 L) foi preenchido em 50 por cento com anel pall. Resultados e discussão No experimento 1, obteve-se baixa remoção de DQO com médias inferiores a 40 por cento e concentração final entre 270 e 750 mg.L-1. No entanto, verificou-se remoção de N-NH4, principalmente na 2ª e 3ª etapas, com médias de remoção entre 43 por cento e 81 por cento , resultando em concentração de 20 a 223 mg.L-1, com influência do TDH. No experimento 2, problemas técnicos durante a instalação e operação inicial e interdição do campus da USP-Leste prejudicaram a adaptação do reator e impediram o seu monitoramento por tempo suficiente para geração de dados consistentes, sendo interrompido na fase inicial. Conclusões A baixa eficiência para DQO provavelmente está relacionada à recalcitrância do lixiviado, ou devido à inibição dos microrganismos por toxicidade. Quanto ao N-NH4, infere-se que o aumento do TDH proporcionou maior tempo de difusão de oxigênio para o sistema wetland, suprindo a demanda das bactérias heterotróficas, o que possibilitou utilização do oxigênio excedente pelas nitrificantes, culminando na oxidação do N-NH4. / Introduction sewage treatment systems, when applied to the treatment of landfill leachate, have not shown good results. Thus it is necessary to develop alternatives for the treatment of leachate. Objective To assess the post-treatment of landfill leachate by horizontal subsurface flow constructed wetland and moving bed biofilm reactor (MBBR). Materials and methods Two experiments were conducted with treatment of the leachate after removal of ammonia by stripping. In experiment 1, horizontal flow constructed wetlands, at bench scale (total volume of 30.8 L), planted with Cyperus papyrus, Heliconia psittacorum and Gynerium sagittatum, and a control without vegetation, were filled with calcareous gravel. The system was fed with leachate diluted in water with different proportions (between 10 per cent and 30 per cent ) with mean COD concentration of between 336 and 750 mg.L-1 and ammonia nitrogen (NH4-N) between 47 and 199 mg L-1. The operation was divided in three stages: (1st) continuous feeding with mean HRT between 2.7 and 5.3 d; (2nd) regime of effluent recirculation to evaluate the effect of increasing the HRT to 21 days; (3rd) continuous feeding with two wetlands units in series, aimed HRT increasing (between 8.1 and 9.9 d) without recirculation. Experiment 2 was implemented on a pilot scale, with a unit of ammonia stripping followed by MBBR and an anoxic biofilter. The MBBR (380 L working volume) was filled 50 per cent with pall ring. Results and discussion In experiment 1, the COD removal was low, with averages below 40 per cent , with effluent concentration between 270 and 750 mg.L-1. However, there was removal of NH4-N, especially in the 2nd and 3rd stages, with average removal between 43 per cent and 81 per cent , resulting in concentration between 20 and 223 mg.L-1, with HRT influence. In experiment 2, technical problems during the installation and initial operation and interdiction of the campus of USP-Leste disrupted the reactor acclimation and precluded the monitoring for sufficient time to generate consistent data for discussion. Conclusions The low efficiency for COD is probably related to the recalcitrance of the leachate, or due to inhibition of microorganisms by toxicity. For NH4-N, it is inferred that the increase of the HRT provided greater time for diffusion of oxygen to the wetland system, meeting the demand of heterotrophic bacteria, which allowed the use of excess oxygen by nitrifiers, culminating in the oxidation of NH4-N.
500

The avian community characteristics of constructed treatment wetlands of South Florida

Unknown Date (has links)
This study compared the avian communities of treatment wetlands in South Florida called Stormwater Treatment Wetlands (STAs) to those in natural marshes and crop lands, and examined factors that influenced the size and structure of the avian communities within the STAs. The STAs contained a more abundant, rich and distinct avian community compared to reference land types. The STAs were dominated by wintering waterfowl, and therefore community patterns fluctuated more seasonally other land types. Within the STAs, density and richness in the fall and winter were much greater in the submerged aquatic vegetation than in the mixed emergent vegetation when waterfowl were present. The STAs maintain two vegetation treatments which enhanced their biodiversity value by supporting distinct avian communities with different migratory strategies This suggests the increase in treatment wetlands could partially offset the loss of natural wetlands, but avian communities in treatment wetlands are not surrogates for natural wetlands. / by Tyler J. Beck. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Page generated in 0.1127 seconds