Thesis (M.S.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: James W. Bauder. Includes bibliographical references (leaves 75-84).

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

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.

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>

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.

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.

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.

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.

The aim of this project was to identify a suitable solution to the problem of landfill leachate at the North Katoomba landfill site. Options were affected by a range of constraints including economics, location and the intrusion of ground water into the landfill. The initial goal was to contain and treat the leachate on site, with the eventual target to discharge into the nearest receiving waters. A constructed wetland option was devised and researched, involving identification of the major pollutants contained within the leachate, developing a concept design and estimating the likely removal efficiencies expected. Investigations identified the primary pollution parameters as microbial and nutrients. Metals were found to be low in concentration although the wetland has the capacity to deal with these pollutants should they become part of the pollution plume. A bench scale constructed wetland system was developed to give an indication of the removal efficiencies. The results suggest that a constructed wetland system would be appropriate for treating landfill leachate at the North Katoomba site. It is recommended that a constructed wetland be established in the field to determine the long term treatment prospects and the potential management problems in a practical application. / Master of Science (Hons)

Thesis (M. L. A.)--University of Hong Kong, 2007. / Title proper from title frame. Includes special report study entitled: Constructed wetland for wildlife, drainage and sewage treatment. Also available in printed format.