Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains vii, 69 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xii, 191 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references (p. 117-119).

Thesis (M.S.)--Baylor University, 2006. / Includes bibliographical references (p. 76-77).

Report (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 87-91). Also available via the Internet.

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.

Treating elevated nutrients, suspended solids, oxygen demanding materials, heavy metals and chemical fertilizers and pesticides in agricultural wastewaters is necessary to protect surface and ground waters. Constructed wetlands (CWs) are an increasingly important technology to remediate wastewaters and reduce negative impacts on water quality in agricultural settings. Treatment of high strength effluents typical of agricultural operations results in the production of methane (CH4), a potent greenhouse trace gas. The objective of this study was to evaluate CH4 emissions from two subsurface flow (SSF) CWs (223 m2 each) treating dairy wastewater. The CWs were implemented at the University of Vermont Paul Miller Dairy Farm in 2003 as an alternative nutrient management approach for treating mixed dairy farm effluent (barnyard runoff and milk parlor waste) in a cold, northern climate. In 2006, static collars were installed throughout the inlet, mid and outlet zones of two CWs (aerated (CW1) and a non-aerated (CW2)) connected in-series, and gas samples were collected via non-steady state chambers (19.75 L) over a nine-month period (Feb-Oct 2007). Methane flux densities were variable throughout the nine-month study period, ranging from 0.026 to 339 and 0.008 to 165 mg m-2 h-1 in CW1 and CW2, respectively. The average daily CH4 flux of CW1 and CW2 were 1475 and 552 mg m-2 d-1, respectively. Average CH4 flux of CW1 was nearly threefold greater than that of CW2 (p = .0387) across all three seasons. The in-series design may have confounded differences in CH4 flux between CWs by limiting differences in dissolved oxygen and by accentuating differences in carbon loading. Methane flux densities revealed strong spatial and seasonal variation within CWs. Emissions generally decreased from inlet to outlet in both CWs. Average CW1 CH4 flux of the inlet zone was nearly threefold greater than mid zone and over tenfold greater than flux at the outlet, while fluxes for CW2 zones were not statistically different. Methane flux of CW1 was nearly fifteen fold greater than CW2 during the fall, representing the only season during which flux was statistically different (p = .0082) between CWs. Fluxes differed significantly between seasons for both CW1 (p = .0034) and CW2 (p = .0002). CH4 emissions were greatest during the spring season in both CWs, attributed to a consistently high water table observed during this season. Vegetation was excluded from chambers during GHG monitoring, and considering that the presence of vascular plants is an important factor influencing CH4 flux, the potential CH4 emissions reported in our study could be greatly underestimated. However, our reported average CH4 fluxes are comparable to published data from SSF dairy treatment CWs. We estimate average and maximum daily emissions from the entire CW system (892 m2) at approximately 1.11 and 6.33 kg CH4 d-1, respectively, yielding an annual average and maximum flux of 8.51 and 48.5 MtCO2-e y-1, respectively.

Dried cattail and bulrush plant pieces in mesh bags were incubated in the constructed wetland treating Pope & Talbot pulp mill effluent. Two ponds planted with each species and two depth ranges in each pond were chosen, to determine decomposition rates. Bags were withdrawn and analyzed at five time points for the cattail and three for the bulrush. Also a laboratory study was conducted, where ground cattail and bulrush material was incubated aerobically and anaerobically. Both species and control were sampled at five time points. The remaining dry mass and the contents of hemicellulose, cellulose, lignin, and silica was examined. Decomposition rates were determined by fitting the data to the single exponential model with the intercept fixed in 1 (100%). An asymptotic model was used to obtain better fit. The sum of squared errors (SSE) was used as a measure of fit. In the field study the ANOVA revealed no change in decomposition with depth. Neither was there a difference between cattail and bulrush ponds. During the first two days only the cell compounds are drastically reduced. Cellulose and hemicellulose start to decline later. Lignin increased slightly during the first half of the experiment. Decay rates from the single exponential model with the intercept fixed were higher than the ones listed for wetlands by Webster & Benfield (1986). The asymptotic model indicates, that there is a fraction, which does not decompose significantly during the time frame of the experiment. It predicts 36% cattail and 53% bulrush material to be left after one year of decomposition. All samples in the laboratory incubation showed strong leaching during the first day (26.5% for cattail, 23% for bulrush). After this the t-test (95% confidence) showed a significant decay coefficient only for the aerobic cattail samples the model with the best fit. These same samples had an increased cell component, and a very small particle size at the last sampling time (120 days). Neither bulrush nor the anaerobic cattail incubations showed the same effect. Cattail and bulrush plants in the field were labeled to observe the senescence. Their height and in the case of cattail the amount of green and dry leaves was recorded monthly. Plants were harvested once a month until February, and the fiber composition was measured. Cattail was completely dry in January, while bulrush still showed green spots in February. Cattail entered the aquatic system mainly by dropping pieces of leaf tips, less by breaking off and losing the outside leaves. In February the average height of cattail plants was 64.7% of the maximum average height in August. Bulrush plants shortened to 84.1% of the maximum average height from September. Most of the bulrush plants died through nutria, a rodent, which is chopping off the plants. Less material was lost by dropping small pieces off the plant tips. / Graduation date: 1994

Constructed wetlands (CWs) utilize the natural mechanisms in wetlands to remove pollutants by physical, chemical and biological processes. CWs are one of the ecological engineering methods to purity water quality and has been experimented to assess their capabilities to remove nutrients from eutrophic water bodies of lakes and reserviors. This study was carried out to compare the removal of nutrients between vegetated and unvegetated CWs. The vertical flow bed was placed in the upstream, while the horizontal subsurface flow bed was set in the downstream. Cannaceae was selected to plant in the vegetated CWs. Two kinds of hydraulic retention time (HRT), 3 days and 7 days, were applied and compared with each other in this study. The experimental results show that no significantly difference between vegetated and unvegetated systems. The removal efficiencies of SS, BOD, NH3-N, TP are measure equal to about 80%, 75%, 80% and 65%, respectively, while the removal efficiencies of TN, OP, and COD were reached about 50% and larger. Both of the two systems show high efficiencies for nutrient removal. In the comparison between the two kinds of HRT¡¦s, the HRT controlled at 3 days presented higher removal efficiencies than that controlled at 7 days.

Thesis (M.S.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Otto Stein. Includes bibliographical references (leaves 41-43).

Thesis (Ph.D.)--Baylor University, 2006. / In abstracts "- and 2" are superscript. In abstracts "3 and 2" are subscript. Includes bibliographical references (p. 105-114).