This study examines the use of bioretention as a strategy to reduce the thermal impact associated with urban stormwater runoff in developing cold water stream watersheds. Temperature and flow data were collected during ten controlled trials at a bioretention facility located in Blacksburg, Virginia. It was determined that bioretention has the ability to reduce the temperature of thermally charged stormwater runoff received from an asphalt surface. Significant reductions in average and peak temperatures were observed. However, this facility was unable to consistently reduce the temperature below the threshold for trout health. The ability of bioretention to reduce runoff flow rates could also serve to reduce the thermal impact. Based on these results it was concluded that bioretention appears to have the capability to reduce the thermal impact of urban stormwater runoff on cold water stream ecosystems. / Master of Science

<p> This thesis focuses on the thermal plasma treatment of non-point source pollutants accumulating in stormwater ponds. Stormwater ponds are constructed as a part of urban non-point source pollution control systems. Pollutants from various sources are collected in the stormwater ponds as sediments. In this work, stormwater sediments were first separated by a filter with an opening of 208μm. The filtered sludge-water was subjected to pulsed arc electrohydraulic discharge (PAED) treatment while the solid part (i.e., wet sludge and dried PAED treated sludge) was subjected to thermal plasma treatment under non-DC transferred and partial transferred operation modes. The results from the PAED sludge-water treatment show that the reduction of TOC in sludge-water was approximately 80% and was greater than 90%, respectively, after 5 minutes and 2 hours of PAED treatment. The accumulated gaseous concentrations of CxHy, CO, C02, S02, H2S and NO emission from sludge-water treatment were 8.2, 3.1, 1.9, 0.32, 0.29 and 0.07 mg/L, respectively, after 2 hours of PAED treatment. The concentrations of volatile elements in sediments such as S, Br, Cl and K decreased approximately 80, 90, 30 and 20% respectively. The solid-phase carbon was observed to be approximately completely removed after treatment. Based on the above results, it can be concluded that PAED successfully degraded organic compounds into C02, CO and CxHy, and converted sulfur and nitrate compounds into S02, HzS and NO. </p> <p> Thermal plasma wet-sludge treatments showed that a reduction of TOC was approximately 52% with argon plasma gas and air flow rates (in the reaction zone) of 24 and 2.4 L/min, respectively. Based on SEM images, wet sludge was melted under partial transferred mode. Thirteen elements with concentration relationships of 0 > Si > Al > Ca > S >Fe> K > Mg > Na > Cu > C > Ti > Cl were quantified by the X-ray energy dispersion technique. The elemental weight percentages of Si, K, Fe and 0 increased with increasing reaction zone air flow rate, while Ca and Cu decreased with increasing air flow rate. Thirty two elements were quantified by Neutron Activation Analyses (NAA) but only 27 elements were above the detection limits. Major elements (concentration> 1000 ppm) with relative concentrations of Ca > Al >Fe> K > Mg > Na > Ti > Cl; minor elements (100 - 1000 ppm) with relative concentrations of Mn > Ba > Sr > Zn; and trace elements(< 100 ppm) with relative concentration were Mo > V > Cr > Br >La> As > Sc > Th> As > Co > Dy > W > Sb > Eu; were determined. Concentrations of Zn, La and Co were enriched 90, 50 and 30% on average respectively, while concentrations of Br, W and As decreased by 80, 50 and 20% on average respectively. The chemical compositions in sludge were quite different after thermal plasma treatment. The average percentages of sand (Si02) and calcite (CaC03) decreased 35 and 10% respectively, while compounds such as KAlSi08, Fe304, NaCl and CaS04 were formed after thermal plasma treatment. Gaseous hydrocarbons, H2S, CO and NO were emitted continuously during the thermal plasma treatment of sludge. Higher reduction of organics and sulfur compounds and suppression of NOx formation were observed in the thermal plasma treatment of wet sludge. The integrated system consisting of PAED sludge-water treatment and thermal plasma wet sludge treatment under partial transferred mode may provide a potential for stormwater pond sediment treatment control. </p> / Thesis / Doctor of Philosophy (PhD)

An increasingly recognized problem in the world is stormwater runoff and its generation of pollutants in urban areas. Stormwater treatment technologies have therefore increased in implementation to prevent this pollution. One of these preventions are detention ponds, which primary function is the equilibration of water, but have also proven to have the capacity to remove many particle-bound pollutants by sedimentation. What's not as known is to what extent. The investigated detention ponds were compared to see to what extent they had accumulated particle-bound elements such as heavy metals, phosphorus and sulphur. This because it is essential to clarify whether they embody ecotoxicological hotspots and if when dredged will have sediment classified as hazardous waste. What was found in this study was that there was no significant difference in accumulation of pollutants or sediment depending on inlet or outlet, a difference between these could still be seen though by looking at the figures. The sediment of some of the detention ponds also had levels of the investigated elements higher than existing guideline values recommend for living organisms in the sediment and could also be classified as hazardous waste when emptied. More investigations need to be done, for example about how hydrology, plant uptake and design affect the sedimentation of pollutants to know for sure how the accumulation of pollutants in detention ponds work.

Phosphorus (P) in stormwater runoff has detrimental effects on water quality and ecosystem health when it reaches surface waters and promotes algal blooms. Constructed wetlands (CWs) have been utilized to combat this problem by containing stormwater and removing excess nutrients. Including filter materials in the design of CWs has shown promise for increasing their capacity for nutrient removal. This mesocosm scale study was conducted outdoors over a 12-month period to evaluate the effectiveness of three filter materials in their ability to adsorb phosphorus, retain water, and support plant life. The filter materials examined were electric arc furnace (EAF) slag, engineered biochar, and sand. All treatments demonstrated positive plant response and the ability to retain water. The EAF slag and biochar removed significant amounts of P from effluent and appear to be suitable materials for integrating into CW design. Sand was found to be ineffective as a P filter.

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The focus of this research was to assess the performance of bioswales in mitigating and treating stormwater runoff from highways and to identify critical parameters that influence the load of pollutants from the drainage area. These bioswales are located in Philadelphia and are part of a project initiated by the Pennsylvania Department of Transportation to upgrade a major roadway (Interstate 95) running through the area. The work included sampling and laboratory analysis of runoff water from 9 storm events to characterize concentrations of contaminants coming from the highway and going in to the bioswales. For one storm event, sampling of vadose-zone and ponded water was included to assess how contaminants move or are retained within the bioswale. The various contaminants include solids, nutrients and metals, which have all been shown to be parameters of concern when dealing with stormwater runoff from highways. In addition, a simulated runoff test was performed to assess the potential risk of a very large storm in mobilizing contaminants within the bioswale. Stepwise linear regression in IBM SPSS was used to analyze the runoff data collected. Characteristics of the rainfall (antecedent dry period, total rainfall, rainfall intensity) were selected as potential explanatory variables to predict contaminant concentration or load. Results of the runoff characterization showed contaminant concentrations that fell within range of literature values from a similar drainage area. Estimated annual loads of contaminants were also in range of what has been observed for highway runoff. Vadose-zone and ponded water sampling showed removal of ammonia, total phosphorus and chemical oxygen demand and build-up of nitrate, total nitrogen and TKN. The build-up was likely due to lack of ion interaction with soil particles, which caused the contaminants to remain in the water. Simulated runoff testing showed no potential for contaminant mobilization within the bioswale but did indicate potential areas of contaminant buildup via observation of a dye tracer. Stepwise linear regressions performed in SPSS showed total rainfall as the most significant predictor of suspended solid, nitrate and total phosphorus load in the bioswales. Results also indicate that there are significant differences between the loads observed for the two bioswales monitored. / Civil Engineering