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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.
41

Turbidity Removal Efficiency And Toxicity Issues Associated With The Chitosan-based Dual Bio-polymer Systems

Hernandez, Rylee 01 January 2012 (has links)
Stormwater runoff can be a great concern in the State of Florida due to the impact the quality of the runoff water can have on the natural water bodies. Stormwater runoff can carry pollutants and sediments which can cause both physical and biological risks in an aquatic ecosystem such as a lake, river, or pond. Polymers, namely the chitosan-based dual polymer system, can be used remove the sediment from this runoff to ensure the safety of the state’s water bodies. Three soils are used in this testing: AASTO soil classifications A-3(sandy soil) and A-2- 4 (silty-sand), and a soil with a fine-grained limerock component. An optimum dose of the chitosan-based dual polymer system is first determined using jar testing. The optimum dose is the dose that reduces the final turbidity to 29 NTUS or below and creates significant flocs. The under dose and over dose are calculated based on the optimum dose. Using these dosages, field scale tests are conducted using two different treatment methods: a semi-passive treatment method and a passive treatment method. Whole effluent toxicity and residual chitosan tests are then conducted on the effluent from the field scale treatment methods. The passive treatment method is the best field scale treatment method when using the silty-sand and the soil with a fine-grained limerock component. The semi-passive treatment method is the best field scale treatment method when using the sandy soil. The passive treatment method with the silty-sand achieves a final turbidity of 123.9 NTUS (88.45% removal). The passive treatment method with the soil with a fine-grained limerock component achieves a final turbidity of 132 NTUS (83.86% removal). The semi-passive treatment method with the sandy soil achieves a final turbidity of 31.43 NTUS (82.04% removal). There is only significant toxicity associated with the tests using iv the effluent from the passive treatment method with the soil with a fine-grained limerock component which only uses the cationic polymer
42

Thermal Pollution Mitigation in Cold Water Stream Watersheds Using Bioretention

Long, Daniel Lewis 24 March 2011 (has links)
This study examines the use of bioretention as a strategy to reduce the thermal impact associated with urban stormwater runoff in developing cold water stream watersheds. Temperature and flow data were collected during ten controlled trials at a bioretention facility located in Blacksburg, Virginia. It was determined that bioretention has the ability to reduce the temperature of thermally charged stormwater runoff received from an asphalt surface. Significant reductions in average and peak temperatures were observed. However, this facility was unable to consistently reduce the temperature below the threshold for trout health. The ability of bioretention to reduce runoff flow rates could also serve to reduce the thermal impact. Based on these results it was concluded that bioretention appears to have the capability to reduce the thermal impact of urban stormwater runoff on cold water stream ecosystems. / Master of Science
43

Development of Effective Procedures for Stormwater Thermal Pollution Potential Risk Mapping

Martin, Clinton James 02 February 2017 (has links)
Thermal pollution of waterbodies occurring from heated stormwater runoff in urban catchments is a growing concern among municipalities in the United States. The U.S. Environmental Protection Agency (EPA) maintains regulatory criteria for temperature of waters of the U.S. as many species of aquatic life depend on an environment that maintains water temperatures below a certain threshold. Thermal pollution from urban stormwater runoff threatens the livelihoods of cold-water fish species, like trout, among other species of wildlife. In order to reduce thermal pollution loading to its streams, a municipality or regulatory authority must first identify the sources of thermal pollution in its waterbodies. This study predicts areas within an urban watershed in the Town of Blacksburg, VA that may be sources of thermal pollution in stormwater runoff by investigating indicators of thermal pollution potential (TPP) through and analysis of land cover types and runoff flow patterns in a geographic information system (GIS) environment. Results of the study provide a theoretical foundation for TPP risk mapping with recommendations for authorities interested in pursuing TPP risk mapping as a tool to guide and focus efforts toward reduction of thermal pollution and land planning. / Master of Science
44

The Impact of Different Stormwater Fee Types: A Case Study of Two Municipalities in Virginia

Dritschel, Amanda Marie 20 June 2016 (has links)
Stormwater user fees (SUFs) are an increasingly popular method of generating revenue for municipalities responsible for implementing complex stormwater regulations through the NPDES permit program. These fees can be created in a multitude of ways, including a flat fee for each parcel, charging by parcel area, charging based on a runoff factor, and many others. As a case study, eight SUFs were applied to the City of Roanoke and the Town of Blacksburg, both in Virginia, to determine the effect each SUF has on how land use type impacts the revenue composition. The City of Roanoke is larger and includes more industrial areas, but less multifamily impervious areas than Blacksburg, which translates differently in the SUFs. Residential parcels comprise the highest percentage of the revenue in all eight SUFs in Blacksburg and four in Roanoke. Open space parcels don't contain much impervious area yet account for up to 27% of the revenue. Industrial parcels comprise more of the revenue in Roanoke, averaging 11.1% compared to 4.6% in Blacksburg. A detailed digitized land cover dataset was compared to Blacksburg's land cover dataset, which resulted in maximum difference of $0.02 per parcel for residential parcel fees. Exemptions of large parcels in Roanoke, like the railroad and airport, if enacted would result in a maximum increase in fees of 15% and a shift of $7,491 of the monthly revenue to the residential parcels. / Master of Science
45

Restoring the Lost Rivers of Washington: Can a city's hydrologic past inform its future?

Millay, Curtis A. 24 May 2006 (has links)
Washington, D.C., like many older U.S. cities, suffers the woes of rapid urbanization and aging infrastructure. The city's combined sewer and stormwater system dumps millions of gallons of raw sewage into the Anacostia and Potomac Rivers over 70 times annually during significant rain events. While many groups, both public and private, attempt to clean the river, billions of dollars are still necessary over several years to remedy the combined sewer overfl ow (CSO) problem alone. Current plans for a solution include constructing large underground storage tanks that store millions of gallons of wastewater during overflow periods. Washington, however, once had a network of waterways that naturally drained the Federal City. At least three major stream systems—the Tiber Creek, James Creek and Slash Run—and over 30 springs flowed within the boundaries of the emerging capital. The waterways, now buried, were victims of urbanization, and flow now only underground, wreaking havoc on foundations and basements and causing sewer backups and flooding. Can a historically-driven investigation of these buried channels lend credence to the resurrection in some form of a network of surface stormwater channels, separate from the municipal sewage system, to solve the city's sewage overflow crisis? The following study is an initial exploration of the re-establishment of waterways through Washington with the purpose of improving the current storm sewer overflow dilemma and exploring the potential urban amenities that they could provide as part of a stormwater management plan for the year 2110. / Master of Landscape Architecture
46

Design Principles and Case Study Analysis for Low Impact Development Practices - Green Roofs, Rainwater Harvesting and Vegetated Swales

Ramesh, Shalini 27 September 2011 (has links)
This thesis on Low Impact Development (LID) Practices provides design guidelines and principles for three important LID practices: green roofs, rainwater harvesting and bioswales. The most important component of the thesis is the qualitative analysis of various case studies based on the LID objectives drawn from the literature review for each LID practice. Through the course of my research, I found that there was no one single source which provided information on the design guidelines accompanied by case examples which could help the designer with built examples where the LID practices have been executed. Therefore, developing this thesis document which provided all this information started as my masters thesis project. The document is designed to be used by people with a variety of expertise like landscape architects, landscape contractors, engineers and clients. The manual is organized into five chapters. The manual details the process of stormwater management and then gradually leads to the evolution of Low Impact Development Practices and detailing out three important LID practices: green roofs, rainwater harvesting, vegetated swales and briefly about infiltration systems. The LID principles outlined in this manual were developed over the last few years to address runoff issues associated with the new residential, commercial and industrial suburban developments. Information to develop this manual has been drawn from numerous sources like the Low Impact Design Strategies developed by the Prince George's County, Maryland, US EPA, Low Impact Development urban design tools and numerous other research papers. It is my hope that the manual will provide adequate information to its users by not only providing design guidelines but also provide built examples through the case studies. / Master of Landscape Architecture
47

The Thickness of Landscape, horizontally and vertically considered

Hazelrigg, George 12 November 2002 (has links)
The McMillan sand filtration plant in Washington, D.C. is a significant industrial landscape that provided safe clean water to much of the capital during 1905-1985. At the outset, the McMillan Commission chose to make the plant and adjacent McMillan reservoir part of the park system it was mapping for Washington. Frederick Law Olmsted Jr. was appointed to landscape the tract, a task completed in 1920. Closed to the public since WWII, the site was abandoned when its operation ended. This thesis looks at its future by exploring the thickness of landscape and the site's discovered geometry. Peeling back its uniformly level 25-acre surface broken only twice by rows of concrete towers, its horizontal layers, vertical elements and strong grids are revealed, offering clues for new design strategies. Examples of how landscape geometries have been considered and works of landscape built elsewhere are reviewed. Recalling water's historically central role in the site, the latter's potential for demonstrating responsible stormwater management and other sustainable practices is emphasized. Local stakeholder interests and proven ingredients of successful urban parks are noted. A design process is outlined that exploits the earlier exploratory findings to reconcile the transition between old and new, deciding what to remove and what to add. Details are provided on the resulting new "memorial park" that both celebrates its history and responds to contemporary interests and needs of the 21st century urban landscape. / Master of Landscape Architecture
48

Improving Urban Watershed Health Through Suburban Infill Design and Development

Franklin, Joshua C. 31 August 2011 (has links)
Up to 75 percent of new construction between 2000 and 2030 may â be redirected inward or into more compact, mixed-use suburban developments (Nelson, 2004). If this assertion is even nearly true, and if the goals of the Clean Water Act are to be met in the next generation of American cities, then we must find feasible and effective ways of improving urban watershed health using retrofit and infill development as a primary means. The aim of this study is to evaluate the patterns and approaches of suburban infill developments in order to determine which methods and extents are deemed capable of improving the health, sustainability and natural services of urban streams and watersheds. Water is considered to be foundational to urban and suburban sustainability and is treated as a primary indicator of overall health and sustainability within the context of this study. This thesis presents three pilot studies that examine urban watershed health using a single case as a vehicle. The studies, in the order they are presented, are: 1) Form- analyzing the relationship between landuse patterns and imperviousness, 2) Planning- relating questions of development scale planning and design to natural and cultural systems at the watershed scale and 3) Valuation- illustrating three possibilities for determining the economic value of improving urban watershed health. / Master of Landscape Architecture
49

Karlstad tätorts dagvattenhantering : En studie om hanteringen av dagvatten ur ett hållbarhetsperspektiv / Karlstad city stormwater management : A study of stormwater management from a sustainability perspective

Svensson, Elin, Adolfsson, Miriram January 2019 (has links)
Dagvattenhanteringen är ett aktuellt ämne i dagens stadsplanering. Forskning som denna studie utgår ifrån visar hur dagens traditionella system inte klarar av kommande klimatförändringar med mer och intensivare nederbörd. Dagvatten för med sig föroreningar samt miljögifter som kväve och fosfor, men även tungmetaller som klorid, olja, organiska miljögifter och bakterier. Det traditionella systemet leder dagvatten ofta rakt ut i våra vattendrag via recipienterna då endast 8 procent av Sveriges dagvatten blev renat år 2016. För en djupare förståelse kring detta utgår studien ifrån teorier inom hållbar utveckling, antropocentrism, ekocentrism samt det rumsliga perspektivet. Materialet består av litteratur, artiklar, tidigare forskning samt fyra intervjuer. Informanterna består av en konsult, en som arbetar på en branschorganisation och två från Karlstad kommun för att få förståelse kring dagvattenhantering, hur en hållbar dagvattenhantering definieras och hur Karlstads kommuns vision för dagvattenhanteringen ser ut. I resultatet för denna uppsats har det framkommit att informanternas syn på dagvatten stämmer överens med Naturvårdsverkets riktlinje av hållbar dagvattenhantering. Karlstad kommuns visioner kring dagvatten lever även upp till denna definition. Utifrån materialet kan uppsatsen visa på att informanterna har en bred kunskap kring framtidens klimatpåverkan på dagvatten samt dess åtgärder. Teorierna har kopplats med resultatet där det går att förstå hur det rumsliga perspektivet påverkas beroende på hur dagvatten hanteras och att en intergenerationell antropocentrism samt svag ekocentrism kan utläsas från intervjuerna. / The stormwater management is topical in today’s urban planning. The research that this study is based of shows how today's traditional system can not cope with future climate change with more intense precipitation. Stormwater also spreads pollution and environmental toxins such as nitrogen and phosphorus, but also heavy metals as chloride, oil, organic pollutants and bacteria. The traditional system often leads the stormwater straight into our waters via the recipients. Only 8 percent of Sweden's stormwater was purified in 2016. For a deeper understanding about this, the study is based on theories in sustainable development, anthropocentrism, ecocentrism and the spatial perspective. The study is based on the theories above, previous research as well as four interviews with a consultant, one who works on a industry sector organisation and two people who works on Karlstad kommun. The people are chosen for a deeper understanding about stormwater, how a sustainable stormwater management is defined and how Karlstad kommuns visions for stormwater management are. The result of this thesis has revealed that the informants view of stormwater is in line with the Swedish Environmental Protection Agency's guideline on sustainable stormwater management. The visions of stormwater in Karlstad kommun also live up to this definition. Based on the empirical data, the essay can show that the informants have a broad knowledge of future climate impact on the subject and its measures. The theories are linked with the result, where it is possible to see how the spatial perspectives are affected depending on how stormwater is managed and that an intergenerational anthropocentrism and weak ecocentrism perspective can be read from the interviews.
50

Men vattnet då? : Samverkan för en mer hållbar dagvattenhantering / But What About the Water? : Cooperation for a More Sustainable Stormwater Management

Wiklund, Lisa January 2022 (has links)
Hållbar dagvattenhantering är ett koncept som, i takt med ökade regnmängder och tät bebyg-gelse, blivit mer och mer uppmärksammat inom stadsplanering. Det handlar om att hitta ettmer robust system för att hantera det dagvatten som uppstår genom att kombinera både rör-och ledningssystem med andra lösningar som fördröjer och renar vattnet innan det når ut tillrecipienten. Samtidigt är samhällsbyggnadsprocessen ofta komplex och involverar många olikaaktörer vilket också gäller för dagvattenhantering. I och med detta uppstår ett antal utmaningarsom problematiserar processen mot att få till en mer hållbar dagvattenhantering. Detta arbetesyftar till att komma underfund med de utmaningar som finns när det kommer till samverkanrelaterat till dessa frågor samt att klargöra hur samverkan kan förbättras för att uppnå en merhållbar dagvattenhantering. I arbetet görs en litteraturstudie vars främsta syfte är att reda ut begreppet samverkan, vad sombidrar till god samverkan och vilka positiva effekter samverkan kan ha i ett projekt. För att sedanreda ut vilka utmaningar och framgångsfaktorer som finns kring dagvattenfrågan genomförs enkvalitativ studie i form av sju intervjuer med personer som på olika sätt arbetar med dagvatten.Dessutom används två analysverktyg, Fyrfältaren och Forum-Arena-Court, för att sortera in debehov och förbättringar som behövs arbetas med. Det framkommer att det finns en del problematik kopplat till samverkan och dagvattenhantering.Det finns främst förbättringspotential när det kommer till att hantera de olika perspektiv ochintressen som kommer med att ha många olika aktörer involverade. Där framstår det som viktigtatt dagvattenfrågan är med tidigt i processen och att det skapas en gemensam målbild kring vadsom ska genomföras i projektet. Utöver detta finns det även en del utmaningar när det kommertill tydlighet kring hur projektet ska genomföras. Här är det viktigt att det finns tydliga riktlinjerfrån kommunens sida samt att se till att det finns en kontinuitet och dialog. Sammantaget finnsdet behov av förbättring kring samverkan och detta skulle kunna möjliggöra vägen mot en merhållbar dagvattenhantering. / Sustainable stormwater management is a concept that, with increasing amounts of rain and densesettlements, has been paid more attention to in urban planning. It revolves around finding amore robust system for managing stormwater by combining systems using pipes with othersolutions that delay and clean the water before it reaches the recipient. At the same time, theprocesses within urban planning are complex and involve many different parties which is alsotrue for stormwater management. Consequently, a number of challenges arise which complicatesthe process of achieving sustainable stormwater management. This study aims to find what thecooperation challenges are and to find out how cooperation can be improved to achieve a moresustainable stormwater management. In the study, a literature study is conducted with the purpose of investigating the conceptof cooperation, what good cooperation consists of and what positive effects it might have ina project. To figure out what the challenges and the factors of success are when it comes tostormwater management, a qualitative study consisting of seven interviews with people workingwith storm water is conducted. In addition, two tools for analysis, Forum-Arena-Court andFyrfältaren, are used to categorize the needs and improvements that need working with. There appears to be some issues regarding cooperation in connection to stormwater management.Mainly, there is potential for improvement when it comes to handling the different perspectivesand interests that come with having several different parties involved. It seems important to makesure that stormwater management is included early in the process and that there is a commonvision regarding what is supposed to be achieved within the project. Moreover, there are also afew challenges in regards to clarity of how the project is to be carried through. It is important tohave clear guidelines from the municipality’s side as well as continuity and dialogue throughoutthe project. To summarize, there are a few areas where improvement is needed when it comesto cooperation and this could possibly lead the way towards a more sustainable stormwatermanagement.

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