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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.
11

Leaching Test with Sawdust fromDifferent Tree Species : Appropriateness of using them as adsorptionmedia in wastewater and in stormwatertreatment

Svensson, Henric January 2010 (has links)
<h2>Abstract</h2><p> </p><p>Bio energy in form of woodchips and sawdust is today commonly stored outdoors in heaps on hardened surfaces, exposed to weather and wind. Any water leaching from these heaps have the potential to be toxic to the environment.</p><p>This paper examines the quality of the water leaching from heaps of four different tree species (oak, pine, maple and beech), by analysing different parameters such as pH, conductivity, colour, COD, BOD<sub>7</sub>, tannins & lignins (T&L) and phenols.</p><p>The results show significant higher leaching values of COD, phenols, T&L and colour from oak compared to the other tree species (pine, maple and beech). These leached substances from woodchips and sawdust were shown in the BOD<sub>7</sub> tests and BOD<sub>7</sub>/COD ratio values to be hard to biodegrade and are therefore not easily removed from the water.</p><p>Hence it is important that wood-based fuel storage conditions are considered in bio energy generation schemes to ensure that the environmental benefits of using woodchips and sawdust instead of traditional fuel are not offset by the potential harm of inappropriate storage.</p><p>The investigation further showed that leaching of highly toxic substances such as phenols can be up to 10 times higher for one tree type (oak) than another (pine, beech and maple). This difference could potentially be found for other tree species not characterized in this study.  Therefore, it is important to consider the constitution of the heaps to be able to apply appropriate storage conditions to avoid these toxic substances in the leached water reaching sensitive watercourses. As some of these substances are hard to biodegrade the treatment applied need a long retention time.</p><p>Another problem is the carbon: nutrient ratio, this water has a high carbon content compared to phosphorus and nitrogen content which might prevent an efficient biodegradation. Adjusting C:N:P ratio with low cost amendments might raise the performance of the biodegradation in for instance, a constructed wetland.</p>
12

A developmental framework proposal for the University of Pretoria's Groenkloof campus

Swart, Jacoba Cecilia 24 November 2008 (has links)
WHAT L.C de Villiers is the official sports-grounds of the University of Pretoria and hosts the High Performance Centre (HPC). This world class sports clinic was designed as a rugby training facility, but is currently used as a training and accommodation centre catering for various sport codes. The HPC has enjoyed great success; to such an extent that the facility is overcrowded and expansion plans are in the pipeline. WHY A twin HPC facility is planned on the Groenkloof campus. This campus has developed sportsfields, existing infrastructure,ample space for development, cultural significance and forms part of the southern gateway of Pretoria. HOW This study investigates how a HPC integrates with Groenkloof campus. Furthermore, stormwater management will be investigated. Lastly a material selection referenced from relevant history will be put together for detail design. / Dissertation (ML(Prof))--University of Pretoria, 2009. / Architecture / unrestricted
13

Components for area-efficient stormwater treatment systems

Milovanovic, Ivan January 2021 (has links)
With progressing urbanisation, treatment of urban stormwater is a vital issue that should be addressed to ensure good water quality in receiving water bodies. Treatment may be performed near the source, with different filter systems using various filter materials, or by using an end-of-pipe method, e.g. a stormwater pond. One constraint in the urban environment is the lack of available space in developed areas, where stormwater treatment facilities are needed the most. Methods developed to treat the stormwater runoff have been the focus of previous studies but the increasing standards of water quality and increasing land constraint pressures demand the further development of stormwater treatment systems. Both laboratory and field experiments are necessary to understand and improve the treatment processes as well as to evaluate how the implemented methods perform under field conditions. The aim of the thesis was to increase the knowledge about the components in stormwater treatment systems that can be used in area-efficient treatment facilities. In order to compare four potential stormwater filter materials (peat, bark, air-blown polypropylene and milkweed), column experiments were carried out using synthetic stormwater that simulated road runoff. Experiments were carried out to evaluate the impacts of the ageing of synthetic stormwater quality during laboratory testing, including dissolved metal concentrations and their impact on the estimation of filter efficiency. In a field study, a full-scale application of a zeolite filter installation was investigated, with a focus on service life and the efficiency of treating copper roof runoff. In order to further investigate a novel sedimentation device, a bottom grid structure (BGS), promoting sediment settling in a smaller area of a stormwater pond, a hydraulic modelling study was conducted to investigate the impact of the cell geometry of the structure on sediment settling and the impact of the structure on pond maintenance and sediment resuspension.  The column tests of four different filter materials showed that bark and peat had higher treatment efficiency for dissolved metals than milkweed and polypropylene, with the order of efficiency being peat&gt;bark&gt;milkweed&gt;polypropylene. All four of the filter materials showed a total metal reduction of over 70%, which could be due to the separation of particle-bound metals in the columns. The ageing of the synthetic stormwater showed that dissolved metals, particularly copper, decreased in concentration, quite rapidly. During one experiment run, the dissolved copper concentration was reduced to 15% of its initial value. In order to account for the concentration changes an equation was proposed that normalised the concentration of dissolved metal over the duration of the experiment. During the observation period of 16 months, the zeolite installation removed 52% to 82% and 48% to 94% of total and dissolved copper, respectively. However, the effluent concentrations were still high (360-600 μg/l). There was also an indication of the decreasing filter performance over time with a prediction that the treatment level of total copper would drop to approximately 25% by the end of the service life of three years. The hydraulic experiments on a scaled model of a BGS showed that wider cells were on average 13% more efficient in trapping the particles than the narrower variant. The cell wall angle also had an impact (tilted walls added to the sedimentation efficiency), although the applicability of such cell structures can be questioned, as this cell shape may hinder maintenance efforts. It was also hypothesised that the inclusion of the BGS in the pond reduces the area needed for sediment settling, thus making the pond more area-efficient and easier to include in an urbanised setting.
14

Performance Analysis of the Ashby Stormwater Retention Pond in Fairfax City, Virginia

Schwartz, Daniel Nathan 06 June 2014 (has links)
Ashby Pond in the City of Fairfax, Virginia was retrofitted to treat runoff from 54.7 hectares of urban land of mixed use. The pond discharges into Accotink Creek, a highly urbanized tributary of the Potomac River and Chesapeake Bay that is listed on the State of Virginia 303(d) list for multiple impairments. The entire multi-state Chesapeake Bay Watershed is subject to Total Maximum Daily Load (TMDL) restrictions on sediment, phosphorus and nitrogen. Virginia and local municipalities assign pollutant reduction credits to retention ponds that meet certain design requirements. However, to actually meet existing and future water quality goals set by TMDLs, it must be proven that such ponds truly provide the water quality benefits for which they have been credited. The inflow and outflow water quality of Ashby Pond was examined over 7 months from fall 2012 to spring 2013. During that period, the pond provided statistically significant reductions of phosphorus, nitrogen and suspended sediment, but not organic carbon or oxygen demand. Ashby Pond had non-significant export of sodium, chloride and calcium. The pond underperformed when compared to state reduction credits for phosphorus load and concentration, but met and exceeded the credits for nitrogen load and concentration, respectively. The pond was under-sized compared to state design standards, and some underperformance should be expected. / Master of Science
15

Land, Water, Infrastructure And People: Considerations Of Planning For Distributed Stormwater Management Systems

Lim, Theodore C. 16 December 2021 (has links)
When urbanization occurs, the removal of vegetation, compaction of soil and construction of impervious surfaces—roofs, asphalt, and concrete—and drainage infrastructure result in drastic changes to the natural hydrological cycle. Stormwater runoff occurs when rain does not infiltrate into soil. Instead it ponds at the surface and forms shallow channels of overland flow. The result is increased peak flows and pollutant loads, eroded streambanks, and decreased biodiversity in aquatic habitat. In urban areas, runoff is typically directed into catch basins and underground pipe systems to prevent flooding, however such systems are also failing to meet modern environmental goals. Green infrastructure is the widely evocative idea that development practices and stormwater management infrastructure can do better to mimic the natural hydrological conditions through distributed vegetation and source control measures that prevent runoff from being produced in the first place. This dissertation uses statistics and high-resolution, coupled surfacesubsurface hydrologic simulation (ParFlow.CLM) to examine three understudied aspects of green infrastructure planning. First, I examine how development characteristics affect the runoff response in urban catchments. I find that instead of focusing on site imperviousness, planners should aim to preserve the ecosystem functions of infiltration and evapotranspiration that are lost even with low density development. Second, I look at how the spatial configuration of green infrastructure at the neighborhood scale affects runoff generation. While spatial configuration of green infrastructure does result in statistically significant differences in performance, such differences are not likely to be detectable above noise levels present in empirical monitoring data. In this study, there was no evidence of reduced hydrological effectiveness for green infrastructure located at sag points in the topography. Lastly, using six years of empirical data from a voluntary residential green infrastructure program, I show how the spread of green infrastructure depends on the demographic and physical characteristics of neighborhoods as well as spatially-dependent social processes (such as the spread of information). This dissertation advances the science of green infrastructure planning at multiple scales and in multiple sectors to improve the practice of urban water resource management and sustainable development. / Doctor of Philosophy in City and Regional Planning
16

Analysis of an Urban Stormwater Bioretention Management Practice in Prince William County, Virginia

Angelo, Suzanne 16 May 2006 (has links)
The performance of an urban stormwater bioretention management practice in the Kingsbrooke Subdivision of Prince William County, Virginia was examined over a one-year period. Bioretention is a relatively new urban stormwater best management practice (BMP) intended to mimic the pollutant-removal characteristics of an upland forest habitat. Typical bioretention areas utilize shallow ponding and highly-infiltrative sandy soils to treat the stormwater runoff from small commercial or residential drainage sites. The Kingsbrooke bioretention area was found to be atypical in several ways, including its relatively large, 14 acre, drainage area and the high clay content of its topsoil. Hydrologic and chemical data were collected by Virginia Tech staff for a total of 8 months in 2003 and 2004. Analysis of pollutant loading data was complicated by the presence of three unmeasured water flows: overland inflow bypassing the inflow gage, and groundwater flows both entering and exiting the bioretention soils. The BMP did reduce peak runoff rates for some storms, but did not significantly reduce total storm volumes because of the combined effects of the large drainage area to BMP area ratio and the poor infiltration capacity of the soil. Pollutant load calculations determined that the site removed about 28% of total suspended solids, 32% of total phosphorus, and about 15% of total nitrogen. Removals of approximately 16% and 7% were observed for lead and zinc, respectively. Although the Kingsbrooke bioretention area did improve water quality, the pollutant removal efficiencies were lower than those reported in the literature from more conventional bioretention areas. / Master of Science
17

Green Roof Performance in Cold Climates : A study on how different plants suited for the subarctic climate in northernSweden affects the performances of green roofs

Hjelm, Jonathan January 2019 (has links)
Increased urbanization leads to an increasing amount of impervious surfaces and a decrease ofthe natural hydrological function. Urban stormwater does thus risk to create high surface flows which could damage the receiving water bodies (e.g. erosion) or the urban area itself (flooding). Integrating more nature-based systems into the urban area increases the natural hydrological function and the risks for high surface flows are lowered. One way of implementing nature-based systems in the urban environment is to install green roofs. Most of the research and development done on green roofs have been focusing on the conditions of central Europe. Installing green roofs with the same vegetation in the subarctic climate of northern Sweden would expose it to a climate it might not be suited for, and growth would be limited. The vegetation helps increase the retaining and detaining capabilities of the green roofs and therefore the purpose of this thesis was to examine if planting native vegetation would help increase thegreen roofs performance in a subarctic climate. Conventional green roofs vegetated with sedum was hypothesized to have lessened retaining and detaining capabilities when placed in cold climates since the vegetation was exposed to a climate it probably was not suited for. It was examined whether planting more native vegetation could help increase green roofs performance. The vegetation was chosen based on Grime´s “universal adaptive strategy theory”, which describes competitors, stress tolerators and ruderals as three different vegetation groups with different survival strategies. Different species from each strategy were selected and planted on the roofs. There were five roofs per survival strategy and five roofs where all strategies were mixed. Conventional sedum vegetation was planted on five roofs to be able to compare green roofs performance. Five control roofs with substrate only and one reference roof made of steel were installed as well. In total, seven rainfall events were analyzed, and few significant differences could be found between the competitors, stress tolerators, ruderals and the vegetation mix. A conclusion is that stress tolerators may help to increase green roof performance the most, but due to the relatively short study period, continued measurements are recommended to draw further conclusions. The survival strategies did improve retention and detention relatively to using sedum vegetation and substrate only. The extent of vegetation coverage does not affect the retention or detention from the green roofs. The competitors, stress tolerators, ruderals and vegetation mix had larger plant mass than the sedum and the increased plant mass is probably the reason for their improved retention.
18

Improved extended detention basin performance through better residence time control

Middleton, John Rob 08 September 2015 (has links)
Extended detention basins are not used for stormwater quality management in many areas of the US because they generally do not achieve the 80% removal of total suspended solids required by many regulatory agencies. The objective of this research was modification of the outlet controls of an existing basin to provide batch treatment of the urban stormwater runoff through efficient control of the hydraulic residence time. A solar powered automated valve and controller were developed and placed on the outlet of an extended detention basin in Austin, Texas to increase the detention time beyond the times achievable using an orifice. This system retained the diverted runoff in the basin for a variable preset period of time. The quality of the influent and effluent of the basin was monitored for concentrations of suspended solids, nutrients, chemical oxygen demand. and total and dissolved metals. The suspended solids concentrations in the basin were controlled by adjusting the residence time of the runoff in the basin to meet the required pollutant reduction. The automated valve can also be used to regulate flow into the receiving waters to control peak flow.
19

Investigation of stormwater particles generated from common urban surfaces

Brodie, Ian January 2007 (has links)
[Abstract]: Pollution due to urban stormwater runoff is a significant environmental issue. Large regional devices including sediment ponds and constructed wetlands are common features in the urban landscape to treat runoff. In keeping with this approach, data requirements to evaluate stormwater impacts have mainly been met by the monitoring of sizeable urban catchments, typically greater than 10ha in area. Urban runoff characteristics have thus been conventionally linked with broadly defined catchment attributes. Land use, as defined by zonings such as Residential, Commercial and Industrial, is an attribute often used to evaluate stormwater runoff from urban catchments.The emergence of Water Sensitive Urban Design (WSUD) in Australia is changing the management focus from the reliance on a small number of large-scale devices to many smaller-scale source controls distributed throughout the catchment. This paradigm shift in stormwater management places greater emphasis on small-scale processes within urban areas. Subsequently there is a need for more knowledge about stormwater generated from specific urban surfaces (roads, roofs, grassed areas etc).The objective of this study was to demonstrate how urban stormwater quality can be managed on the basis of urban surfaces. The study involved the collection of data for typical urban surfaces and the development of predictive models to estimate stormwater quality. A series of case studies is provided to illustrate the use of surface-related data and modelling tools in stormwater management, particularly in the context of WSUD.Non-Coarse Particles (NCP), defined as suspended solids less than 500μm in size, was selected as the stormwater pollutant under consideration. NCP is divided into the following particle size classes; Very Fine Particles (VFP, <8μm), Fine Particles (FP, 8-63μm) and Medium Particles (MP, 63-500μm). Laboratory methods to determine the concentration of these particle classes within stormwater runoff were adapted and refined from current standard methods. Organic content of each stormwater particle class was also determined.An innovative device, the flow splitter, was developed to collect runoff samples from urban surfaces. The flow splitter was designed to obtain a composite flow-proportional sample, necessary to derive the Event Mean Concentration of stormwater particles. Hydraulic and sediment testing of a prototype flow splitter confirmed that the device is an accurate and unbiased sampling method.Flow splitters were installed at five monitoring sites within inner city Toowoomba, Australia. The sites have small catchments (50 to 450m2 area) representative of urban impervious areas (galvanized iron roof, concrete carpark and bitumen road pavement) and pervious areas (grassed and exposed bare soil). Overall, runoff from 40 storms with rainfalls from 2.5mm to 64.3mm was sampled during the period December 2004 to January 2006.A scatter plot analysis identified potential correlations between measured NCP loads and basic rainfall parameters such as rainfall depth and intensity. An exponential-type trend, consistent with many washoff models, is evident between load and average rainfall intensity for all surfaces. A composite index, referred to as the Rainfall Detachment Index (RDI), was found to be better than average rainfall intensity in explaining a relationship between NCP load and storm rainfall characteristics.The insight gained from the RDI led to the development of a particle Mass Balance Model for impervious surfaces. Depending on the surface type, the model was able for provide reasonable estimates (R2 = 0.74 to 0.97) against the measured NCP loads. Simpler analytical methods for particle load estimation were also developed in the study. A total of five methods were produced. An error analysis was conducted to compare the performance of each method to accurately reproduce the measured NCP loads. The analysis also included three methods used in current practice, which performed poorly compared to the new modelling techniques.The analytical methods provide useful tools in urban stormwater planning. The Mass Balance Model and measured surface-specific data were used in a number of case study examples to demonstrate possible applications. The applications included assessments of 1) the relative contribution that different urban surfaces make to the particle load in runoff; 2) how surface-specific data can be directly transferred to represent a large-scale urban catchment located in a different climate; 3) the particle loads generated from Residential and Commercial land uses; 4) the effect of exposed areas of bare soil on the particle loads from a Residential catchment; 5) the effect that widespread adoption of rainwater tanks may have on particle concentration in Residential urban runoff and 6) the particle load reductions by the use of a grass swale to treat road runoff.
20

Big boxes and stormwater

Fite-Wassilak, Alexander H. January 2008 (has links)
Thesis (M. S.)--Architecture, Georgia Institute of Technology, 2009. / Committee Chair: Dagenhart, Richard; Committee Member: Elliott, Michael; Committee Member: Green, David

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