Despite the technology advancement, degradation of water quality due to stormwater continues to be a significant threat to the water and ecosystems due to the exponential growth of industries and agricultural enterprises that discharge stormwater. These anthropogenic activities are the sources of high nitrogen and phosphorus quantities in stormwater, which is responsible for eutrophication phenomena and deterioration of public health. Floating Treatment Wetlands (FTWs) are a potential solution to this problem. Both microcosm and mesocosm level studies were conducted for the effective removal of nutrients in stormwater wet detention ponds with different sorption media under varying nutrient concentrations and weather conditions. Water depth, percent area coverage of the FTWs and littoral zone emergent plants were varied in order to determine nutrient removal efficiency before implementing in an actual pond. Focus has also been placed on the observations of macrophyte-epiphyte-phytoplankton interactions in order to understand temporal characteristics of ecological phenomena. Water quality parameters included Total Nitrogen, Total Phosphorus, Orthophosphate, Nitrate-Nitrogen, and Ammonia-Nitrogen in addition to in-situ parameters such as pH, Dissolved Oxygen, Temperature and Chlorophyll-a. Results clearly indicate that an FTW filled with sorption media of 80% expanded clay and 20% tire crumb can significantly promote the biomass growth. Different levels of nutrient concentrations did affect the plants’ growth and cold temperature in late winter was detrimental to growth. To make the system more viable irrespective of the seasonal weather conditions, the adoption of mixed vegetation is highly recommended in the FTWs implementation. It is also recommended that, the positioning of the floating wetlands should not be in the vicinity of the outlet of the pond as assimilated nutrient under the mat might increase the nutrient concentration in the discharged water. Finally, One-way ANOVA test is performed to check whether or not iv these grouped microcosms and mesocosms with differing experimental setup can be deemed statistically significant

No description available.

Two locations, Lake Ivanhoe and the Maitland interchange of Interstate 4, were selected to study the impact of bridge runoff on receiving water bodies. The Lake Ivanhoe location includes two similar bridges, one without scuppers and one with scuppers. The Maitland interchange site has several borr ponds which drain to Lake Lucien. Samples were collected from Lake Ivanhoe below the bridges and in the open lake away from the bridges. Also samples were collected from the east pond, west pond, and lake Lucien, at the Maitland interchange. Samples included water, sediments, plants and benthos to detect differences, if any, in heavy metal concentration due to sampling location. Heavy metals tested included: ZN, Cu, Cr, Cd, Pb, As, Fe, and Ni. Dissolved oxygen, temperature profiles and secchi desk transparency were measured in the field. Additional water quality parameters such as pH, turbidity, carbon and phosphorus were evaluated. Results indicated significant differences in specific heavy metal concentrations exist between samples collected beneath a bridge with scuppers compared to samples collected beneath a bridge without scuppers. Also, the drainage ponds appear to contain more heavy metals than the adjacent Lake Lucien at the Maitland interchange.

Lake Eola, in downtown Orlando, was the subject of extensive research to determine the impact of stormwater runoff to the lake and possible management alternatives. The focus of this research was stormwater treatment by chemical coagulation followed by detention. Phosphorus was the main parameter targeted for removal. Various chemical parameters were also evaluated included: TSS, VSS, NVSS, COD, TKN, NH3, TOC, TP, Ca, As, Cd, Cu, Cr, Ni, Mg, Zn, Fe, and Pb. The chemical coagulants used for this research included: alum, ferric chloride, and lime. The study involved settling column tests for the various treatment methods to determine stormwater settling characteristics and pollutant removal rates by depth and time. Detention of the runoff in the column for 120 minutes resulted in average removal rates of 55% for TSS and 30% for TP. Both alum and ferric chloride coagulation followed by 60 minutes of settling resulted in average removal rates of over 90% for both TSS and TP. Lime coagulation followed by 60 minutes of settling resulted in over 50% removal for both TSS and TP. Regression analysis was used to develop equation relating pollutant removal with time and settling velocity. Isoconcentration lines were also developed to predict pollutant removal rates for specific parameters.

The settling characteristics of urban stormwater runoff emanating from the Lake Eola Watershed (Orlando, Florida) were evaluated through a series of 7 column studies. The percentage removal that occurred due to sedimentation was observed for various stormwater pollutants and constituents. These included the General Water Quality Parameters: Total Suspended Solids, Non-volatile Suspended Solids, Volatile Suspended Solids, Chemical Oxygen Demand, Total Kjeldahl Nitrogen, Ammonia Nitrogen, Total Organic Carbon, and Total Phosphorus. The metals parameters: Zinc, Cadmium, Arsenic, Nickel, Copper, Magnesium, Iron, Lead, Chromium and Calcium were also considered. The results of the settling analysis indicates that the quality of Lake Eola stormater can be improved by plain sedimentation of detention as convincing removals were displayed by the solid parameters displayed trends of weak removal. Regression equations were developed that describe percent removal as a linear and logarithmic function of time and settling velocity. Isoconcentration lines were also developed for total suspended solids and total phosphorus removals. In addition, the effect of this treatment on the productivity of Lake Eola was assessed in terms of existing trophic state models.

The Stormwater Management and Design Aid (SMADA) is a computer model formulated to assess stormwater runoff quantity and quality. Applicable theory is reviewed to introduce a discussion of the modeling methodology. A pre- vs. post-development design objective can be incorporated to evaluate runoff quantity and quality for single or multiple land use watershed. Detention and retention facilities are considered and conveyance systems for runoff transmission can be sized. Initial design assessments and consistent design review and evaluation are possible. SMADA is written in the BASIC language and is executed in the interactive mode. No computer cards are required and data input is quite self-explanatory. The model is easily adaptable to table-top mini-computers.

Diversion of the first flush of storm runoff to a detention basin for pollutant removal is an efficient way to control nonpoint source pollutant in urban areas. This can be achieved by a diversion box and detention basin system. To numerically simulate the response of the system to a design rainfall event and the associated pollutant loadings for a given drainage area, a desk top model has been developed for"user-friendly"' application in personal computers. Hydrographs and pollutographs are generated at the inlet and outlet of the diversion box and the detention basin.These hydrographs and pollutographs are examined and the peak outflow and peak pollutant concentrations are compared with allowable outflow and pollutant concentration for urban stormwater quality and quantity management. This model is designed for both the analysis and design of the system. / M.S.

Stormwater management basins (SWMB) are used to mitigate urban runoff. The Virginia Department of Transportation relies on dry detention basins planted with mowed turfgrass. However, these basins often retain water; resulting in cattail (Typha spp.) and tree colonization. Managing agencies request cattail eradication and trees are also removed. However, if trees were allowed to remain they could alter basin dynamics, making conditions unsuitable for cattails. In a greenhouse study we tested the impact of three shade (heavy, medium, full sun) and soil moisture (dry, moist, flooded) treatments on cattail growth. After two months, cattail biomass indicated a strong interaction between soil moisture and shade (p<.0001). Increases in shade and reductions in soil moisture resulted in decreased biomass and rhizome length. Heavy shade and dry soil produced the most reductions in cattail growth (95% less biomass, 83% smaller rhizomes than cattails in full sun and flooded soil). However, considerable growth reductions still occurred in medium shade and moist soil (66% for biomass and 74% for rhizome lengths). In a field study in four unmaintained SWMB in Virginia, environmental data (litter layer, water table, soil organic matter, etc.) and vegetation composition (cattail and other herbaceous biomass, and woody vegetation influence index) were collected from 100, 0.25-m2 plots. Principal component analysis indicated cattails and trees occupy opposing environmental spaces. Water table is most strongly correlated to cattail biomass. While these results suggest trees could eliminate cattails from SWMB, more research is needed to determine the long-term impacts of trees on basin function. / Master of Science

Interest in infiltration structures to control peak runoff in urban areas has increased in recent years. The work reported here is a study of infiltration trenches in unsaturated soil. The infiltration rates and the water content distributions in soil calculated by Fok's model and a finite-difference model are compared for both the Ida silt loam soil and the Webster clay loam soil considering the capillary zone effect due to groundwater table. A computer program for hydrologic routing in infiltration trenches has been developed with the infiltration rate calculated based on a 3-dimensional cumulative infiltration equation. The 3-D cumulative infiltration equation developed in this study is recommended for the analysis and practical design of infiltration trenches, since it is easy to use and inexpensive in computation. An infiltration trench with overflow has been examined allowing the overflow not to exceed an allowable discharge to downstream. It has been found that the surface infiltration due to overland flow does not significantly alter the infiltration rate from a trench. It has also been found that a long narrow trench is more effective for water to infiltrate into soil than a short wide trench for the same trench area( length x width ). The hydraulic conductivity of a soil is an important factor in the design of an infiltration trench, whereas the porosity and the effective capillary potential have minor effects. / M.S.

A statistical model has been developed to study the long-term behaviour of a stormwater detention unit. This unit stores a portion of the incoming runoff, corresponding to the empty space available in the unit, from which runoff is pumped to a treatment plant. The objective is to avoid, as much as possible, the discharge of untreated runoff to receiving bodies of water. The model was developed by considering the arrival of independent runoff events at the urban catchment. The process variables of event depth, duration, and interevent time were treated as independent, identically distributed random variables. A storage equation was formulated from which the probability of detention unit overflow was obtained. With this distribution it was possible to define the trap efficiency of the unit in terms of the long-term fraction of the runoff volume trapped by the storage unit. The trap efficiency expressions define storage/ treatment isoquants, which represent the combinations of storage capacity, treatment rate, and the sewer system runoff trapping capacity, which provide a fixed level of runoff control. A pollutant load model was also formulated, based on a first-order washoff model. This model was used to define pollutant control isoquants. Optimal values of the required storage capacity and treatment rate were obtained by treating the isoquants as production functions. Applying the results of production function theory, a cost minimization problem was solved for the value of the storage capacity and treatment rate, for prescribed runoff and pollutant trap efficiency levels. The results obtained with the statistical model compared well with results obtained from major simulation models. The statistical approach offers an advantage in that no simulation is required to obtain the isoquants, as the expressions are analytical, thus greatly simplifying the optimization process. Also, the evaluation of the storage unit pollutant trap efficiency can be easily evaluated for any type of pollutant whose washoff rate is known. / Ph. D.