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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.
51

Assessing constructed wetlands for beneficial use of saline-sodic water

Kirkpatrick, Amber Denise. January 2005 (has links) (PDF)
Thesis (M.S.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: James W. Bauder. Includes bibliographical references (leaves 75-84).
52

Wastewater renovation with soil depth as influenced by additional treatment of septic tank effluent /

Duncan, Carla S., January 1994 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 78-86). Also available via the Internet.
53

Retention performance and hydraulic design of constructed wetlands treating runoff waters from arable land

Koskiaho, J. (Jari) 29 August 2006 (has links)
Abstract Agriculture is the main source of nitrogen (N) and phosphorus (P), which are the nutrients accelerating the eutrophication of waters in Finland. Hence, mitigation measures are needed to reduce the nutrient loading from the arable land. Since Finland's accession to the EU in 1995 and the subsequent adaptation to its agri-environmental policy, constructed wetlands (CWs) have been one of the mitigation measures for which farmers may receive agri-environmental subsidies. The aim of this study was to find out how efficiently such CWs are able to retain the loading and how they should be designed and dimensioned in order to optimize their performance. Particular attention was paid to CW hydrology and hydraulics, since the dynamics of the water flowing through a CW is the major factor governing retention. Water quality and flow measurements were made in three CWs located in agricultural watersheds in southern Finland during 1999-2002. Hydraulic properties were examined in 2 of the CWs by simulations with 2-dimensional hydrodynamic and water quality models. According to the calculations of material fluxes, the maximum annual retention was 72% for solid material (TSS), 67% for total P and 40% for total N. The lowest retentions were slightly negative, because the CW with the smallest CW-to-watershed area ratio (0.5% in the Alastaro CW) sometimes acted rather as a source than a sink of nutrients. The highest percent retentions were found in the Hovi CW with the largest CW-to-watershed area ratio (5%). In terms of mass per CW area, the Hovi CW retained 25 kg of total P and 300 kg of total N per one hectare per one year. In the Hovi CW also dissolved reactive P retention was high (49% in situ and 34% in laboratory microcosm experiments), obviously due to high contents and low P saturation of Al and Fe oxides of the CW soil. The basic underlying reason behind the high retentions of both dissolved nutrients and particulate matter in the Hovi CW was the long water residence time coupled with high hydraulic efficiency. In the deep part of the Hovi CW, near-bottom increase of dissolved O2 was found in phase with diurnal temperature changes. The oxygen transport by this kind of convective circulation of CW water inhibited near-bottom anoxia and thus decreased the risk of P desorption. According to the hydrodynamic simulations coupled with simulated tracer tests made for the Hovi CW, a 40% improvement in hydraulic efficiency was achieved by baffles directing the main flow to optimally exploit the CW area. The rectangular, elongated shape of the Alastaro CW also showed fairly high hydraulic efficiency. Hydrodynamic simulations were also coupled with a sediment transport model, which proved to be a useful method in predicting the change of TSS concentrations in CWs. Hourly datasets of inflow and outflow revealed high attenuation of runoff peaks in the well-designed and -dimensioned Hovi CW. The hourly outflow modeled with the reservoir routing method corresponded to the observed with a reasonable accuracy. When carefully designed, painstakingly implemented and wisely located, CWs may – even in cold climate – efficiently contribute to agricultural water pollution control.
54

Manipulating biotic and abiotic factors to enhance the remediation of agri-industrial wastewater in pilot-scale constructed wetlands

Welz, Pamela Jean January 2012 (has links)
Philosophiae Doctor - PhD / As a consequence of various cellar activities the wine industry produces copious volumes of potentially hazardous wastewater each year. South Africa is one of the top ten wine-producing countries, making the successful treatment of cellar effluent an important environmental obligation in this country. Constructed wetlands (CWs) are resilient to the seasonal input fluxes associated with agri-industrial waste and are ideal systems for the in-situ treatment of cellar effluent in small to medium-sized wineries not connected to municipal reticulation systems. In a project sponsored by the Water Research Commission of South Africa, a number of studies were undertaken to assess the remediation of winery wastewater and common components of winery wastewater in sand-filled pilot-scale constructed wetlands operated in batch mode. This thesis contains the results of three studies. The first study evaluated the temporal aspects of CW equilibration as a basis for future studies of system response to amendment. Microbial biomass and hydraulic conductivity values were monitored and microbial community fingerprints were obtained using denaturing gradient gel electrophoresis. The study showed that microbial community fingerprinting provides a valuable tool to assess the time-scales of microbial equilibration, which was found to be in the order of 100 days. In the second study, the biodegradation and mineralization of ethanol by acclimated and non-acclimated microbial populations in CWs were compared. By increasing the influent ethanol concentration at incremental intervals (incremental priming), the biodegradative capacity was significantly enhanced. At an influent COD concentration of 15 800 mg/L, no volatile fatty acids were detected in the effluent of an incrementally primed system and the maximum effluent COD measured was 180 mg/L. In contrast, an identical, unprimed system, amended with a lower concentration of COD (7587 mg/L), exhibited a maximum effluent COD concentration of 1 400 mg/L, with the metabolites butyrate and propionate accounting for up to 83% of the effluent COD. It was conclusively demonstrated that the use of incremental priming, together with the batch mode of operation enhanced long-term function of the CWs. In the third study, the removal of the phenolic component of winery wastewater was evaluated in CWs, as well as in sand columns and microcosms. It was found that at low influent phenolic concentrations in CWs, complete organic removal was accomplished, but at high concentrations, there was incomplete substrate removal and an accumulation of potentially toxic metabolites, including catechol. The sand provided a suitable substrate for the treatment of phenolic-laden waste, and both biotic (48%) and abiotic (52%) removal mechanisms effected the removal of model phenolics. Prior acclimation of microbial communities increased the biodegradation rate of phenolic acids significantly.
55

The Current Water Balance in Syria : Evaluating the potential contribution of Constructed Wetlands as a treatment plant of municipal wastewater in Al-Haffah

Drgham, Mohamad Mubarak January 2020 (has links)
The future projection of climate change suggests the strong need of improved systems to the re-source management systems. In Syria, the current water resource management systems are weak, and the country has no resilience to the scarcity of water resources in the region. In 2007 a drought has crippled the Syrian economy and impacted the life of millions of Syrian People, the devastating occurrence of the drought had larger impacts due to the lack of water resource management sys-tems and irresponsibility of use. This study investigates the current management systems that Syria has, and the supply and demand of the country, of which is aimed for with the term (water balance) that refer to the flow of water in and out of the system. Furthermore, a constructed wetland design is introduced as a system to treat municipal wastewater of the town Al-Haffah, located east of Latakia city of which is situated at the Mediterranean coast, on the Costal basin. All the data avail-able relevant to the investigation has been used in the case study, nevertheless some assumptions has been made due to lack of available data. The introduced system is later evaluated in regards of water need for agricultural purposes in Al-Haffah. The design with the assumed current value, in worst case scenario could save annually (48.57%) of the groundwater abstraction for agricultural purposes, Or (29.14%) of the total water demand for the agricultural practices in Al-Haffah. Whilst, in best case scenario, if two third of the required water for agriculture is met with rainfall the system saves (145.7%) of the assumed groundwater abstraction, Or (87.43%) of the total an-nual required water. / <p>2020-06-05</p>
56

Development of the Urban Wetland Filter for Managing Phosphorus in Stormwater

Rosenquist, Shawn E. 08 April 2010 (has links)
Degradation of surface water quality by excess nutrients in stormwater is a substantial environmental and economic problem in the U.S. Phosphorus (P) is often the limiting nutrient for harmful algal blooms and the best target to prevent degradation. Natural treatment strategies such as constructed wetlands (CW) demonstrate effective and economical P management but obstacles exist to implementation. Biological P removal has large land requirements that limit the use of best management practices (BMP) in high land-value areas. Various BMP also utilize sorption processes (SP) for P removal but variations in performance and finite sorption capacity limit SP as a viable long-term removal strategy. However, by understanding variability and making sorption capacity renewable, SP could provide, with shorter retention times, a space-efficient, long-term removal strategy. This multi-study research program developed the urban wetland filter (UWF), a concept intended to overcome the unique limitations of high land-value areas to natural treatment strategies and provide a low-cost, easily implemented BMP to meet P management goals while harvesting sequestered P for use as a fertilizer. Experimental factors included substrate and influent properties pertinent to understanding performance variation and optimizing microbial iron (Fe) reduction for rejuvenation of sorption capacity. Regarding performance, modeling identified major sources of variability including, by order of importance, magnitude of a solution/substrate concentration gradient, length of the "antecedent dry period" between loadings, and pH. Field-scale results confirmed this multifactor dependence of P-removal while also supporting the inclusion of cast-iron filings in substrate to improve P removal. Regarding rejuvenation, results indicated that microbial Fe reduction is capable of releasing previously sequestered P from substrates. A sufficient carbon source was necessary, but microbial inoculation was not necessary to facilitate Fe reduction, which released most of the previously sequestered P, albeit more slowly than P sequestration. Field-scale results indicated that Fe reduction might occur faster under field conditions, possibly due to humic acids, and that inclusion of cast-iron filings enabled additional P removal after rejuvenation by providing a conservative source of Fe for the creation of new sorption sites; however, cast-iron filings may also limit the release of P during rejuvenation. / Ph. D.
57

Treatment of Bio-Oil Refinery Stormwater by a Simulated Constructed Wetland: A Sustainable Management Alternative

Kraszewska, Katy 09 May 2015 (has links)
Contaminated stormwater discharge is a major concern in the United States due to a steady increase of harmful pollutants entering fresh water sources. The many congressional mandates that require local governments to reduce the impact of storm water discharge on the natural ecology have greatly increased the need for economically and environmentally viable solutions to pollution reduction. One such solution is that of constructed wetlands. Previous research conducted at the Sustainable Bio-products Department at Mississippi State University demonstrated the feasibility of kenaf fiber and wood shavings to remove toxins and crude oil from the bio-oil process water. This study proposes to amend contaminated storm water runoff from a biomass to bio-oil conversion facility through a simulated constructed wetland. The constructed wetlands were contaminated with varying dilution levels of bio-oil process water in a series of six phases. It was hypothesized that the contaminated rainwater can be remediated by constructed wetlands and safely released back into the native waterways. This study concluded that there was a significant decrease in biological oxygen demand (BOD) and micro-toxicity over a ten day cycle within the constructed wetlands for the lower levels of contaminated stormwater. A comparative screen of the bacterial community within the wetlands during the contamination process showed a similar trend in species richness and composition for the first three Phases of contamination. There was a shift in richness and diversity for the final three Phases of contamination after ten days within the constructed wetlands. The constructed wetlands were successful at lowering BOD and toxicity levels and achieving permissible pH levels when the concentration of contaminated stormwater was less than or equal to 400x dilution. Much of the BOD reduction was due to volatilization of the contaminated wastewater. When the concentration of contaminated water exceeded 300x dilution, the constructed wetland were only successful at achieving permissible pH discharge levels. Better results may be achievable with longer residence time in the wetlands.
58

Constructed Floodplain Wetland Effectiveness for Stormwater Management

Ludwig, Andrea L. 04 August 2010 (has links)
A 0.2-hectare wetland was constructed in the floodplain of Opequon Creek in Northern Virginia as a best management practice (BMP) for stormwater management. The research goals were to 1) determine if wetland hydrology existed and quantify the role of groundwater exchange in the constructed wetland (CW) water budget, 2) estimate wetland hydraulic characteristics during overbank flows, and 3) quantify the event-scale nutrient assimilative capacity of the constructed wetland. CW water table elevations and hydraulic gradients were measured through an array of nested piezometers. During controlled flooding events, stream water was pumped from the creek and amended with nutrients and a conservative tracer in two seasons to determine hydraulic characteristics and nutrient reduction. Samples were collected at the inlet, outlet structure, and at three locations along three transects along the wetland flowpath. Water table elevation monitoring demonstrated that wetland hydrology existed on the site. The mean residence time of the wetland was found to be 100 min for flow-rates of 4.25-5.1 m3/min. Residence time distributions of the high and low marsh features identified a considerable degree of flow dispersion. Manning's n varied between macrotopographic features and was significantly higher in the spring event as compared to the fall event, likely due to the presence of rigid-stem vegetation. Average wetland n was 0.62. Total suspended solid concentrations decreased with increasing residence time during both experiments. Mass reduction of pollutants were 73% total suspended solids (TSS), 54% ammonia-nitrogen (NH3-N), 16% nitrate-N (NO3-N), 16% total nitrogen (TN), 23% orthophosphate-phosphorus (PO4-P), and 37% total P (TP) in the fall, and 69% TSS, 58% NH3-N, 7% NO3-N, 22% TN, 8% PO4-P, and 25% TP in the spring. Linear regression of mass flux over the event hydrograph was used to determine pollutant removal rates between the wetland inlet and outlet. Pollutant removal rates were determined through linear regression of mass flux and were higher in the spring event than in the fall. Dissolved nitrogen species were more rapidly removed than dissolved phosphorus. TSS, TP, and TN removal were greater and faster than dissolved nutrient species, suggesting that physical settling was the dominant removal mechanism for stormwater pollutants. / Ph. D.
59

Modelagem do desempenho de "wetlands" construídas.

Lautenschlager, Sandro Rogério 14 May 2001 (has links)
Este trabalho contém uma revisão bibliográfica relativa à eficiência de wetlands construídas para a remoção de nitrogênio total e fósforo total. Também foram revisados diversos modelos matemáticos para a simulação desta remoção e foi efetuada uma análise crítica destes modelos. Foram empregados dados de domínio público da eficiência de remoção de nutrientes por wetlands construídas de fluxo superficial. Estes dados foram analisados procurando-se calibrar um modelo matemático para a simulação da eficiência de remoção. Observou-se, porém, que estes dados apresentam comportamento bastante complexo, sendo que, por vezes, a eficiência de remoção medida apresenta valores negativos. Partiu-se então para uma abordagem estatística destes dados, a qual poderá servir para a avaliação do risco de ocorrência de desempenho insatisfatório envolvido no dimensionamento de wetlands construídas. / This work presents a bibliographic review about the efficiency of constructed wetlands to remove total nitrogen and total phosphorus. Also many mathematics models to simulate this removal were reviewed and a critical analysis of these models was carried out. Public domain data about the removal efficiency of nutrients by constructed wetlands of surface flux were used. These data were analyzed in order to fit a mathematical model to simulate the removal efficiency. However it was found that these data present a complex behavior, including the occurrence of negative values. A statistical approach of these data was then carried out as an attempt to assess the risk of unsatisfactory performance involved in the design of constructed wetlands.
60

Modelagem do desempenho de "wetlands" construídas.

Sandro Rogério Lautenschlager 14 May 2001 (has links)
Este trabalho contém uma revisão bibliográfica relativa à eficiência de wetlands construídas para a remoção de nitrogênio total e fósforo total. Também foram revisados diversos modelos matemáticos para a simulação desta remoção e foi efetuada uma análise crítica destes modelos. Foram empregados dados de domínio público da eficiência de remoção de nutrientes por wetlands construídas de fluxo superficial. Estes dados foram analisados procurando-se calibrar um modelo matemático para a simulação da eficiência de remoção. Observou-se, porém, que estes dados apresentam comportamento bastante complexo, sendo que, por vezes, a eficiência de remoção medida apresenta valores negativos. Partiu-se então para uma abordagem estatística destes dados, a qual poderá servir para a avaliação do risco de ocorrência de desempenho insatisfatório envolvido no dimensionamento de wetlands construídas. / This work presents a bibliographic review about the efficiency of constructed wetlands to remove total nitrogen and total phosphorus. Also many mathematics models to simulate this removal were reviewed and a critical analysis of these models was carried out. Public domain data about the removal efficiency of nutrients by constructed wetlands of surface flux were used. These data were analyzed in order to fit a mathematical model to simulate the removal efficiency. However it was found that these data present a complex behavior, including the occurrence of negative values. A statistical approach of these data was then carried out as an attempt to assess the risk of unsatisfactory performance involved in the design of constructed wetlands.

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