The phosphorus removal characteristics of several gravel-based constructed wetland systems (CWSs) in the treatment of secondary sewage effluent was studied.Investigations were conducted on water quality parameters (redox potential, pH, dissolved oxygen and temperature) which affect phosphorus adsorption to substrata.Laboratory phosphorus adsorption experiments on Richmond CWS gravel substrata, a gravel used in Griffith CWS trials and a locally available soil, Hawkesbury sandstone, involved ion-exchange experiments and calculation of Langmuir and Freundlich adsorption isotherms and column adsorption/desorption trials.Six steelworks by-products were investigated in laboratory studies, to determine their potential for use as phosphorus adsorbers in a CWS: granulated blast furnace slag(GBF), blast furnace slag(BF), steel slag(SS), fly ash(FA), bottom ash(BA) and coal wash(CW).The ability to adsorb phosphorus was then correlated to the chemical attributes of each substratum.Of the six steelworks by-products screened in laboratory-based studies as substrata for P removal in a CWS, BF and SS slags showed the most potential due to their high phosphorus adsorption capacity and useable matrix size.Further research is recommended to evaluate the sustainability of using slags for P removal (as well as other contaminants present in wastewater), using full scale CWSs, which should include an evaluation of any likely environmental impacts using leachability and toxicity studies. / Doctor of Philosophy (PhD)(Environmental Science)

Thesis (M. L. A.)--University of Hong Kong, 2007. / Includes special report study entitled: Water level control technology in constructed wetland. Title proper from title frame. Also available in printed format.

Five unique but related studies were conducted at the Oregon State University Dairy Wetland Treatment System (OSUDWTS), Corvallis, OR. The research site consisted of six parallel wetland cells, which were built in 1992 and began receiving concentrated dairy wastewater in the fall of 1993. Hydrologic, hydraulic, and water quality data were collected at the site for three years. The five resulting studies were: 1. the prediction of evapotranspiration (ET) from wetlands; 2. the development of a hydrologic model and water budget for the OSUDWTS; 3. a preliminary investigation of the hydraulics of the OSUDWTS; 4. an overall evaluation of the treatment performance of the OSUDWTS and applicability of current constructed wetland design methods to livestock wastewater wetlands; and 5. the development of a conceptual model for nitrogen removal in constructed wetlands. Average ET rates for the wetland cells were found to be 1.6 times as great as the Penman- Monteith alfalfa reference ET. Specific crop coefficients were 1.72, 2.32, and 0.57 for bulrush, cattails, and floating grass mats. The detailed hydrology model predicted daily water levels very accurately (R��=0.95) and showed seasonal rainfall and ET could increase or decrease the average detention time by as much as 18%. Tracer studies indicated that non ideal flow existed in the wetlands. Actual detention times were found to be an average of 43% shorter than theoretical detention times. Tank-in-series and plug flow modified by dispersion models were inadequate at describing the observed tracer response. Constructed wetlands were shown to be able to reduce a high percentage of most waste constituents in concentrated livestock wastewaters. Average reductions for COD, BOD, TS, TSS, TP, TKN, NH��� and fecal coliforms were 45, 52, 27, 55, 42, 41, 37 and 80%, respectively. Rate constants for volumetric and areal first-order plug flow models were found for each wastewater constituent. Overall, both models were fair at predicting wastewater reduction at the OSUDWTS. A conceptual model of nitrogen cycling showed denitrification to be the most important process for nitrogen removal in constructed wetlands. However, low dissolved oxygen in constructed wetlands limits nitrification, which in turn limits denitrification. / Graduation date: 1997

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Jacob L. Bowman, Dept. of Entomology & Wildlife Ecology. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 169-180).

Due to various components within the landfill sites, the water qualityof landfill leachate, which has high consistency of COD, BOD and nutrients, is unsteady. Using traditional sewage treatment plant to treat leachate should be designed and built to fit the unsteady water quality, which is usually time consuming and high expenditured. Therefore, application of constructed wetland treatment systems as altanatives may solve such kinds of problems According to the experimental results of this study, referring to the effect of cleaning the controlling substances, the SSF (sub-surface flow system) constructed wetland system performed better than the FWS (free-water surface system) one, which was because FWS was usually operated in an opening water areas, which exposured to the air causing stink in the inflow site of influent, and meanwhile caused problems of virus-transmitting mosquitoes. . Thus, it was suggested to use SSF system in treating landfill leachate. In this study, we found that the average removal efficiencies of pollutants in the leachate were high in the constructed wetland systmes (phosphate 73%, total phosphorous 70¢H, total nitrogen 57%, NH3-N 77¢H, COD 43% ). In addition, the BOD in the effluent from the systems could reach the outflow standard guideline in Taiwan (30 mg/L). Hence, using constructed wetland systems to solve those problems arisen from landfill leachate is expandable. We also found that the aquatic plant species of reed (Phragmites australis) that we used in this study could not grow well and was invaded by aphid due to the limitary environment in the landfill site and lack of biodiversity, which could not generate a good natural food chain. On the other hand, it was found that the plant species of evergreen (Dracaena sanderiana) could grow healthily and present high removal efficiencies for pollutants. Since the leachate was lack of biodegradable organic carbon sources used for denitrification, in the final test run of this study, we run an experiment of adding organic carbon sourcecs (fructose and molasses) into the constructed wetland systemis to test its effect on denitrification. The experimental results showed that the addition of organic carbon sources could significantly increase the efficiencies of denitrification to let more nitrate removed from the leachate, especially for molasses, which could increase the denitrification efficiency above 90%.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (M.S.)--Wildlife and Fisheries Sciences Dept., South Dakota State University, 2008. / Includes bibliographical references. Also available via the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 230-2̀49). Available also in a digital version from Dissertation Abstracts.

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