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  • 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.
71

Constructed wetlands as an appropriate treatment of landfill leachate.

Bricken, Elizabeth Colomb. January 2003 (has links)
One of the main environmental problems associated with the disposal of waste on land is the release of liquid emissions from the site. This wastewater, known as leachate, is a product of the biodecomposition of the waste and filtrates from the landfill once the moisture saturation of the fill has been reached. The chemical composition of leachate is variable over time and between sites. Regardless of these variables, the main pollutants of concern in the leachate are ammonia and organics, both of which can cause environmental degradation in relatively low concentrations. Worldwide and in South Africa, leachate has either been directly released into the environment or into the local domestic sewage system. As more has been learned about the human and environmental health risks associated with these disposal methods, there has been a new focus in waste management toward treating the leachate at the source as part of the broader focus of sustainable landfilling. One of the treatment options being used is constructed wetlands (CW) due to the physical and chemical transformation mechanisms in these biological systems. This treatment process has been demonstrated to be effective as a final polishing treatment for leachate, and it is considered a technology appropriate in the South African context. Therefore the aim of dissertation is to ascertain the use of constructed wetlands as an appropriate treatment option for untreated methanogenic landfill leachate by determining the efficiency of ammonia and organic removal in a pilot-scale vegetated submerged bed (VSB) constructed wetland (CW) planted with Phragmites australis. During the 22-week treatability trial the VSB achieved an ammonia concentration removal efficiency of 91% and mass removal efficiency of 87%. Despite this substantial reduction of ammonia, the VSB was unable to achieve the required discharge standard. There were erratic fluctuations in both the treatment efficiencies for COD and BOO, and the results show no evidence of constant reduction of organics during the treatability trials. This is due to the refractory nature and the low biodegradability of the organics that remain in methanogenic leachate as suggested by the low BOO to COD ratio. Due to the low biodegradability of the organics, a biological treatment system, such as a VSB, will not be able to reliably meet the required discharge standards. Other passive treatment options or a combination of systems need to be explored in order to both satisfy legislative requirements and be appropriate in the South African context. / Thesis (M.Sc.)-University of Natal, Durban, 2003.
72

Temporal effects on orhophosphate removal from municipal wastewater in a subsurface-flow constructed wetland

Womack, Michael January 1996 (has links)
Orthophosphate removal from wastewater in a subsurface-flow constructed wetland (SFCW) was studied during the fall of 1995. The SFCW consisted of a cell with an impervious liner, filled with 1.27 to 3.81 cm river rock and planted with common reeds (Phragmites australis) and soft-stem bulrushes (Scirpus validus). Municipal wastewater was pumped through the wetland and comparisons were made between inlet and outlet orthophosphate concentrations. Comparisons were also made at locations within the cell. A mean orthophosphate reduction of 62% with a range of 91% to 32% was observed for the duration of the study. An ANOVA test showed a significant reduction of orthophosphate in the wetland cell during the study. A regression analysis indicated that inlet wastewater temperatures played a significant role in orthophosphate removal, while outlet wastewater and ambient air temperature were not a significant factor.Keywords: Subsurface-Flow Constructed Wetlands, Orthophosphate, Municipal Wastewater, Water Chemistry, Nutrients. / Department of Natural Resources and Environmental Management
73

Reedbeds for the treatment of greywater as an application of ecological sanitation in rural Costa Rica, Central America

S.Dallas@murdoch.edu.au, Stewart Dallas January 2005 (has links)
The widespread practice in Latin America of separating greywater from blackwater at the domestic level lends itself to the application of Ecological Sanitation, or Ecosan. In this research simple, low-cost subsurface flow wetlands, or reedbeds, were investigated not only for their potential in treating the greywater component but also to evaluate their acceptance as an appropriate Ecosan technology in rural Central America. The hypothesis for this thesis is that Ecological Sanitation, namely via reedbeds for the treatment of greywater can improve sanitation in rural Central America. The first aim of this research determined that untreated greywater was having a significant negative impact on the water quality of the local streams of Monteverde in Costa Rica (the site of this research) and that the associated public health risks will continue to increase in line with population growth. Local residents expressed strong dissatisfaction with the current situation and were supportive of any means to improve it. The second aim of this research was to determine if reedbeds designed according to the principles of Ecosan could provide a healthier, affordable and more sustainable sanitation alternative suitable for rural areas. As a result five case study reedbed systems were designed and installed. All these reedbeds made use of locally available materials and incorporated low-maintenance design features, and research with a local plant species determined a robust macrophyte suitable for use in these systems. The ability of low-cost reedbed systems to successfully treat greywater was demonstrated. The Costa Rican guidelines for wastewater reuse were found to be overly restrictive in regards to fecal coliform limits (<1,000cfu/100mL) and may inhibit the wider uptake of reedbed systems if enforced. Despite this the uptake of the reedbed technology was strong and more than ten systems were installed in Costa Rica as a result of this research. An innovative environmental services contract, the first of its kind in Costa Rica, was developed to ensure on going funding for operation and maintenance of a four-household reedbed system. The third aim was to specifically investigate the use of waste plastic (PET) bottle segments as an alternative media in reedbeds to conventional crushed rock, or gravel. Twelve mini-reedbeds, or cells, incorporating PET media and plants as the two variables, were monitored through wet and dry seasons. This experiment demonstrated that reedbeds incorporating PET segments were able to achieve comparable removal of fecal coliform and BOD when compared to conventional media reedbeds, and at a significantly reduced cost. The local plant species Coix lacryma-jobi enhanced the performance of all reedbeds, most notably in the PET-based reedbeds, which was attributed to the considerably greater root biomass achieved in these systems as compared to conventional media systems. This research has demonstrated that reedbeds incorporating simple, low-maintenance design features are able to provide an affordable and appropriate technology for the treatment of greywater in rural Latin America.
74

The ecotourism potential of the Barber Inlet Wetlands, South Australia /

Higginson, Gareth Edward. January 2000 (has links) (PDF)
Thesis (M.Env.St.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 2000. / Bibliography: leaves 127-134.
75

Ultraviolet disinfection system for constructed wetlands /

Ly, Jong Chan. January 1900 (has links)
Thesis (M.S.)--Humboldt State University, 2008. / Includes bibliographical references (leaves 40-44). Also available via Humboldt Digital Scholar.
76

The potential impact on mosquito larvae by threespine stickleback (Gasterosteus aculeatus) and mosquitofish (Gambusia affinis) in four constructed wetlands /

Simpson, Nicholas P. January 1900 (has links)
Thesis (M.S.)--Humboldt State University, 2008. / Includes bibliographical references (leaves 63-68). Also available via Humboldt Digital Scholar.
77

The role of plants in the removal of nutrients at a constructed wetland treating agricultural (dairy) wastewater /

Gottschall, Natalie, January 1900 (has links)
Thesis (M.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 66-71). Also available in electronic format on the Internet.
78

Optimization of nutrient removal along with minimization of methyl mercury production in the pilot-scale constructed wetland

Chavan, Prithviraj V. January 2008 (has links)
Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "May 2008." Includes bibliographical references. Online version available on the World Wide Web.
79

La selection d'un milieu filtrant utilisé dans un marais artificiel pour la déphosphatation des eaux usées municipales /

Liu, Ling, January 1996 (has links)
Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 1996. / Document électronique également accessible en format PDF. CaQCU
80

Habitat selection and food-web relations of Horned Grebes (Podiceps auritus) and other aquatic birds on constructed wetlands in the Peace Parkland, Alberta, Canada

Kuczynski, Eva Christine. January 2009 (has links)
Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on July 10, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Ecology, Department of Biological Sciences, University of Alberta." Includes bibliographical references.

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