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<p>Excess nutrients are currently impacting the ecosystem, fisheries, and recreational use of Lake Simcoe. The objective of this study was to determine the importance of groundwater as a pathway for nutrient input during base flow periods to a landfill impacted urban stream in Barrie, Ontario, which flows directly into the lake. A characterization of a 28 m reach was created using sediment and water level data, and a groundwater flux map of the stream was creating using heat tracer methods. This data was combined with the shallow groundwater nutrient concentration distribution measured with multi-level piezometers and diffusion samplers to calculate nutrient discharge. Such fine-scale measurements of nutrient discharge using groundwater-based data like these have not previously been reported. The water flux results were then extrapolated to a larger 460 reach (Site B) of Dyment’s Creek, and combined with groundwater contaminant data from that reach to derive a crude estimate of nutrient discharge at a larger scale. Groundwater soluble reactive phosphorus (SRP) and ammonium concentrations were much higher than stream concentrations. Estimates of total SRP discharge ranged from 3.6 to 8.1 g/d at Site A and 38 to 108 g/d at Site B, and ammonium discharge ranged from 66 to 218 g/d at Site A and 757 to 2043 g/d at Site B. This study showed that groundwater is an important pathway for nutrients to enter Dyment’s Creek, and this pathway that must be considered when addressing nutrient input to Lake Simcoe.</p> / Master of Science (MSc)

Soil-bentonite cutoff walls are commonly used to contain contaminants in the subsurface. A key property in determining the effectiveness of a cutoff wall is its hydraulic conductivity. There are important difficulties and uncertainties regarding the accuracy of commonly used methods of measuring the hydraulic conductivity of cutoff walls. When predicting contaminant transport through cutoff walls, common practice is to use the average hydraulic conductivity of the wall. There are some cases, however, such as circumferential cutoff walls with inward hydraulic gradients, where it is also important to consider the variability in hydraulic conductivity from point to point in the wall in contaminant transport studies. A pilot-scale facility was envisioned where subsurface barrier issues such as those mentioned above could be studied. In 1998, the Subsurface Barrier Test Facility (SBTF) was constructed. In this facility, pilot-scale subsurface barriers can be installed using real construction equipment and tested in a controlled environment. The effectiveness of various methods of measuring the hydraulic conductivity of cutoff walls was studied by building and testing three pilot-scale soil-bentonite cutoff walls at the SBTF. The following currently used test methods were evaluated: API tests on grab samples, lab tests on undisturbed samples, piezometer tests (slug tests), and piezocone soundings. The use of slug tests in cutoff walls was improved in this research in the areas of avoiding hydraulic fracture and accounting for the close proximity of the trench walls. The SBTF allows for measurement of the global, average hydraulic conductivity of an installed pilot-scale cutoff wall, which is a useful value to compare to the results of the above-mentioned tests. The two main factors differentiating the results of the different test methods used for the pilot-scale walls were remolding and sample size. Remolding of the API samples significantly reduced the hydraulic conductivity of these samples compared to the hydraulic conductivity measured in lab tests on undisturbed samples, which were of similar size. For the other tests, the degree and extent of remolding were less significant compared to in the API tests. For these tests, the scale of the measurement is believed to be the main factor differentiating the results. Hydraulic conductivity was found to increase as the sample volume increased, with the global measurement of the average hydraulic conductivity producing the highest value. The influence of variability in hydraulic conductivity on contaminant transport through cutoff walls was studied from a theoretical standpoint using the one-dimensional advection-diffusion equation. Charts were developed that can be used to estimate the flux through a cutoff wall based on knowledge of the average hydraulic conductivity of the wall and an estimate of the variability in hydraulic conductivity. Data sets of hydraulic conductivity from lab tests on soil-bentonite samples from four cutoff wall case histories were used to estimate typical values of variability. The contaminant transport analyses showed that the effect of variability may be significant when the hydraulic gradient opposes the concentration gradient, which is the case for a circumferential cutoff wall with an inward hydraulic gradient. The goal of a circumferential cutoff wall with an inward hydraulic gradient is to reduce the outward diffusive flux of contaminant by inducing an inward advective flux. The effect of variability in hydraulic conductivity is to reduce the effectiveness of this scheme. / Ph. D.

Worldwide water distribution infrastructure system is old and deteriorating. A water system with its myriad appurtenances (including pumps and valves and tanks) is susceptible to hydraulic transients resulting in high and low pressure waves alternatively passing through the network. While both low and high pressure events structurally tax the already weak system, there is copious evidence indicating intrusion of contaminants into the drinking water pipes from the pipe's exterior environment due to low pressure events associated with water hammer phenomenon. These contaminants enter into the drinking water as the home plumbing system is a passive recipient from the water main. While the major (municipal) system is readily recognized as a vast infrastructure system of nearly 1,409,800 km of piping within the United States, the minor (plumbing) system that is at least 5 to 10 times larger is generally not well analyzed. In this study, an experimental plumbing rig was designed and implemented that replicates the range of pressures encountered in actual minor water distribution systems. This research addresses how a pressure transient triggered within a house and from municipal systems can impact the service line with a possible suction effect. Experimental results on low pressure events and the accompanying numerical modeling showed good agreement. The experiment also enabled visualization of the various pressure transient phenomena. It is demonstrated that hydraulic transients triggered from water mains result in low pressures events (up to -10 psig) in service lines which can allow possible intrusion of microbial and chemical contaminants at the service line. Structural integrity of service line and hydraulic integrity at water mains should be maintained to minimize any public health risks. In the USA, about 90% of residential drinking water plumbing systems use copper pipes. Pinhole leaks in copper plumbing pipes have become a nationwide concern because these leaks cause property damage, lower property values, and result in possibility of adversely affecting homeowners' insurance coverage. In addition, resulting mold damage may cause health concerns. This research also addresses the concerns of the affected homeowners by enabling them to decide on whether to continue to repair or replace their plumbing system, the factors to be considered in a replacement decision, and the type of material to use for replacement. Plastic pipes such as PEX (cross-linked polyethylene), CPVC (Chlorinated Polyvinyl Chloride), and copper are considered in present analysis. Other alternatives include an epoxy coating technique on the existing piping systems, without the need to tear into walls. Multiple attributes of a plumbing system including cost (material plus labor charges), taste and odor impacts, potential for corrosion, longevity of the pipe system, fire retardance, convenience of installation or replacement, plumber or general contractor's opinions or expertise, and proven record in the market are considered. Attributes and material rankings are formalized within the framework of the preference elicitation tools namely AHP (Analytical Hierarchical Process). Surveys are conducted with selected homeowners in pinhole leak prone area in Southeastern US Community to observe their revealed and stated preferences. Participants' overall preference tradeoffs are reported in addition to comparing their revealed and stated preferences. Health effects, taste and odor of water turned out to be the most important factors from the survey. In real life, however, homeowners were not well aware of these safety issues related with plumbing materials. It is recommended that water professionals should work on bridging the gap between public perception and research results related to major and minor systems. / Ph. D.

Contaminant transport modeling is being used more often at petroleum hydrocarbon contaminated sites in an attempt to aid engineers in evaluating the feasibility of natural attenuation as a remediation alternative in groundwater systems. In this research, a three-dimensional sequential electron acceptor computer model, SEAM3D, developed by Waddill and Widdowson (1997) was used to simulate contaminant transport at a leaking underground storage tank site in Beaufort, South Carolina. Gasoline containing benzene, toluene, ethylbenzene, and xylene (BTEX) as well as methyl tertiary butyl ether (MTBE) leaked into the subsurface at the site late in 1990, and monitoring of the water table elevations and contaminant concentrations began in 1993. Using the field data, the groundwater flow model MODFLOW was used to develop and calibrate a flow model for the Laurel Bay site using GMS (Groundwater Modeling System) v2.1. MODFLOW was coupled with the SEAM3D contaminant transport model, and the available concentration levels were used to calibrate, verify, and validate the site model. The results indicated that SEAM3D simulated complex, interconnected processes including biodegradation, and the transport of multiple hydrocarbon compounds, electron acceptors, and end products over time and space at a specific petroleum hydrocarbon contaminated site. Once the model was calibrated and verified, the model output was used to study the changes in contaminant mass distribution, contaminant mass loss, and mass loss rates for each terminal electron accepting process (TEAP) over time. It was found that the natural attenuation capacity of the aquifer was insufficient to stabilize the plume and prevent it from reaching the defined point of contact (POC). Contamination was shown to have reached the POC by 1994, just four years into the simulation. Results indicated that despite oxygen limitation within the BTEX plume, aerobic biodegradation was responsible for the greatest amount of mass loss, close to 70 %, relative to the sum of the anaerobic processes after 20 years. / Master of Science

Emerging contaminants (ECs) are chemicals such as pharmaceuticals and personal care products that have been detected in various environmental matrices, including drinking water supplies at trace concentrations (ng/L-ug/L or ng/kg-ug/kg). Current wastewater treatment plant technology is largely ineffective at removing ECs. The objectives of this investigation were to: 1) determine the occurrence of ECs in private well water supplies in Montgomery and Roanoke County, VA 2) quantify the concentrations of three ECs in selected private water supplies; 3) examine the relationship between water quality constituents (nitrate, bacteria, pH and total dissolved solids) to EC occurrence in private water supplies; and 4) determine the ability of the MicroEvapTM, a novel wastewater treatment technology, to remove ECs from secondary wastewater effluent. In partnership with the Virginia Household Water Quality Program, 57 private water supplies were sampled and tested for the occurrence of 142 ECs and 43 other water quality constituents. Up to 73 ECs were detected in the sampled private water supplies. Higher numbers of ECs detected in the tested private water supplies were related with nitrate >1 mg/L, total dissolved solids >250 mg/L, and the presence of total coliform bacteria. Results indicate the MicroEvapTM technology had >99% removal effectiveness for all 26 tested ECs from three secondary wastewater effluent. With the increasing detection of ECs in water bodies, it is essential to understand the occurrence of ECs and environmental predictors of EC presence in different water matrices and continue to develop water treatment technology capable of treating wastewater for EC removal. / Master of Science

Syftet med denna rapport var att utreda hur föroreningsmängder och föroreningskoncentrationer i dagvattendammars sediment påverkas av markanvändningen i avrinningsområdet. Sedimentprovtagning skedde under april 2019 i tre dagvattendammar i Gävle, med olika markanvändningar: industri, villaområde samt två avrinningsområden innehållande trafik. Markanvändningen ”trafik vid Västerbacken” hade en trafikintensitet på cirka 2000 bilar/dygn och ”trafik vid Hamnleden” en intensitet på 7000 bilar/dygn. Provtagningen utfördes med rysskannborr och sedimentdjup mättes för att kvantifiera sedimentvolymen i dagvattendammarna. Proverna skickades till laboratorie för analys av metaller, fosfor, alifater, aromater samt polycykliska aromatiska kolväten [PAH]. Dagvattendammen med markanvändning industriområde hade sedimentet med högst föroreningskoncentrationer, följt av villaområde – trafik vid Hamnleden – trafik vid Västerbacken. Resultaten för denna studie visar att inga markanta skillnader kan ses vid jämförelse av föroreningskoncentrationer i sedimentet, utifrån omgivande markanvändning. Markanvändningarna visade liknande koncentrationsmönster i de grafiska figurer som jämfördes. Resultatet kan bero på att dagvattendammarna ligger geografiskt nära och därmed kan bli påverkade av samma atmosfäriska nedfall och bakgrundshalter. Det förväntades inte att föroreningskoncentrationerna i villaområdets sediment skulle vara näst högst. En förklaring kan vara den högre halten organiskt material i villaområdets sediment, vissa föroreningar tenderar att binda starkt till organiskt material. Däremot sågs stora skillnader mellan dagvattendammarnas föroreningsmängder i sedimentet (jämförelsetalet ”fastlagd förorening per år”), vilket återspeglades av sedimentvolymen. Störst mängd föroreningar och störst sedimentvolym sågs i dagvattendammen med markanvändning industriområde. I fallande skala följde trafik vid Hamnleden – trafik vid Västerbacken – villaområde. Resultatet kan bero på skillnader i andel partikulära fraktioner i dagvattnet från respektive markanvändning, där industriområdet i så fall har störst andel partikulära fraktioner enligt resultatet i denna studie. Beräkningar utfördes i StormTac för teoretisk föroreningstransport i inkommande dagvatten till dagvattendammarna. Beräkningarna genererade i totalmängder (lösta och partikulära fraktioner). När föroreningstransporten jämfördes med ”fastlagd förorening per år” för villaområde sågs att föroreningstransportens mängder var markant större, vilket delvis kan förklaras med att totalmängder jämfördes med partikulära mängder. En slutsats som dras är att omgivande markanvändning påverkar föroreningsmängderna i sedimentet och sedimentvolymen, snarare än koncentrationerna. / This thesis addresses how human activities in the catchment area could influence the contaminant concentrations and amounts of contaminants in the sediments of stormwater ponds. Sediment sampling was done in April 2019. The storm water ponds had different land uses: industrial, residential (detached area) and two land uses of traffic with different intensities; “traffic by Hamnleden” (7000 cars/day) and “traffic by Västerbacken” (2000 cars/day). Samples were taken with a Russian corer and sediment depth was measured to quantify sediment volume. Samples were sent to laboratory for analysis of metals, phosphorus, aliphatics, aromatics and polycyclic aromatic hydrocarbons [PAH]. The stormwater pond with industry as land use had the highest concentration of contaminants in the sediment, followed by residential area – traffic by Hamnleden – traffic by Västerbacken. The results of this study showed that the land use concentrations of contaminants were all similar, and the patterns of concentration in the graphic figures were similar. The results could be explained by the narrow geographic area in which the three storm water ponds are situated. They could be affected by the same atmospheric downfall which could even out the concentrations. It was not expected that the residential area would have one of the highest concentrations in the sediment. This could be explained by the high content of organic matter, as some contaminants create strong chemical bonding with organic matter. Bigger differences were seen for the amounts of contaminants in the sediments and the comparative figure “fixated amount of contaminant per year”. The land use industry had the highest amount of contaminants followed by traffic by Hamnleden – traffic by Västerbacken – residential area. This is probably due to differences in particle quota in the storm water coming from the land uses. Calculations were done for the amount of transported contaminants in stormwater, via the watershed management tool and model StormTac. The calculated transportation of contaminants resulted in total amounts of contaminants, meaning both dissolved and particulate fractions. The calculations from StormTac were compared with the comparative figure “fixated amount of contaminant per year” for the land use residential area, and the amounts were significantly higher for the calculated transportation. This could partly be explained by comparing total amounts with particulate amounts. A conclusion of this report is that land use affects the amounts of contaminants and sediment volume in the studied storm water ponds, rather than the concentrations.

The continuous demand on new residential and economic areas of the modern society has to face up with problems posed by polluted sites related to former industrial activities, typically located in suburbs areas. These sites, known as brownfields, are often located nearby navigable rivers to facilitate transport operations of industrial manufacturing, which increase their potential environmental threat due to the possible migration of pollutants in groundwater to surface water bodies through groundwater discharge. In this context, the objective of this research, performed in the scope of the FP6-IP AquaTerra project, was to contribute to a better assessment of the risk of groundwater contaminant dispersion for a brownfield located next to the Meuse River (Belgium), in a context where strong groundwater - surface water interactions prevail. The brownfield of interest corresponds to the site of the former coke factory of Flémalle. Resulting from industrial activities, soil and groundwater located in the alluvial aquifer are heavily contaminated with various types of organic (BTEX, PAHs, mineral oils...) and inorganic (As, Zn, Cd...) pollutants. To do so, detailed characterisation campaign was performed, consisting of, on the one hand, classical field experiments such as pumping tests, injection tests and tracer experiments; on the other hand, advanced and original field experiments such as detailed monitoring of groundwater - surface water interaction and dynamics, and the development and application of an innovative tracer technique, the Finite Volume Point Dilution Method (FVPDM), used to quantify and monitor groundwater fluxes. Monitoring and field works data was subsequently used to develop and calibrate a groundwater flow model using the finite difference code MODFLOW, with an automatic parameter estimation approach based on an original combined regional scale (zonation) and local scale (pilot points) approach. A transport model was also developed using MT3DMS and calibrated using tracer experiments performed in the brownfield. This groundwater flow and transport model was used to better quantify the dynamics of groundwater - surface water interactions and to model various scenarios of contaminant dispersion through the aquifer - river system. For these scenarios, benzene was considered because it is one of the main pollutants encountered in the site, its large solubility and mobility in groundwater and its acute toxicity. These scenarios were established considering various groundwater flow conditions (steady state vs. transient) and various hydrodispersive processes possibly affecting the mobility of benzene in groundwater, namely advection, hydrodynamic dispersion, sorption - desorption and, as evidenced by the research results of the University of Neuchâtel (Switzerland), benzene degradation under sulphate reducing conditions. These simulations indicate that benzene attenuation is mainly controlled by ongoing benzene degradation processes, aquifer heterogeneity and river stage fluctuations. Based on this analysis, the risk of benzene dispersion is low, and monitored natural attenuation (MNA) is a valuable option with (1) monitoring benzene at control planes downstream from the sources; (2) further investigation on risk of sulphate depletion in the alluvial aquifer; and (3) further investigation on mobilisation/immobilisation of heavy metals related to dynamics of organic pollutant plumes.