In conventional wastewater treatment, biological nutrient removal (BNR) depends on bacterial assimilation for phosphorus removal and nitrification+denitrification for nitrogen removal, with the resulting loss of the fixed nitrogen resource. Alternatively, treatment by microalgae allows for assimilative removal of both phosphorus (P) and nitrogen (N) thereby avoiding the oxygen demand of nitrification and preserving fixed N for fertilizer use. Paddle wheel mixed high-rate ponds have much higher algal productivity than typical oxidation ponds, but even high-rate ponds often cannot grow sufficient algae to completely assimilate the N and P in domestic wastewater. Algae growth in high-rate ponds is usually limited by the inorganic carbon concentration. Addition of carbon dioxide to high-rate ponds, for example from flue gas, eliminates this limitation and accelerates algae growth and nutrient assimilation. This laboratory study explored the extent to which soluble N and P are removed simultaneously by CO2-enriched algae cultures. Algal polycultures were grown on diluted domestic wastewater media that were manipulated to obtain a wide range of N:P ratios (2.5:1 to 103:1). In addition, two levels of trace metal concentrations were studied. Media feeding was semi-continuous. The variables monitored included N and P removals, the range of N:P ratios in the algal biomass, biomass production, and alkalinity. To achieve removal of total N and P, suspended solids also must be removed prior to discharge. Since flocculation and settling is a preferred method of algae removal, the effects of low dissolved nutrient concentrations and media composition on algae sinking potential (settleability) were also investigated. The low trace metal cultures achieved >99% total ammonia nitrogen (TAN) removal for N:P ratios 2.5 through 30 and >98% dissolved reactive phosphorus (DRP) removal for N:P ratios 2.5 through 60 (with one exception at N:P-20). This removal was due to the growth of 180-500 mg/L algal volatile solids. Effluent concentrations were <0.1 mg/L TAN for N:P 2.5 through 30, and <0.5 mg/L TAN for N:P-60. DRP effluent concentrations were ≤0.02 mg/L DRP. After 24 hours of settling in beakers, nearly all cultures had total suspended solids (TSS) concentrations <40 mg/L. Alkalinity consumption increased with increasing N:P ratios. For cultures with the higher trace metal concentrations, nutrient removal was similar: >96% of TAN and >95.9% DRP removal for all N:P conditions. However, settling with these media was poor. TSS concentrations after 24-h of settling were >100 mg/L. No clear relationship for alkalinity was found for these cultures. N:P ratios in the algal biomass correlated with the N:P ratios in the media, except for control cultures that did not receive wastewater. No relationship was found between settling and the N:P ratios of the media or biomass. Nitrogen-fixing algae thrived in media containing N:P ratios of 2.5:1 and 5:1. Algae were found to be plastic in their cellular N:P ratios (4.6 to 63, with wastewater media) which allowed them to simultaneously remove both dissolved N and P to low levels, while growing settleable biomass. These results indicate that CO2-enriched high rate pond systems would be useful in simultaneously removing N and P from wastewaters with a wide range of N:P ratios.

Evidence-based dentistry (EBD), an evolving educational tool that started its rise in the late 1990’s and early 2000’s, is being used more every year in dentistry. EBD combines the most current scientific and clinical evidence with the dentists’ expertise and the patients’ needs and preferences to formulate the best option to treat the patient. Since patients are taking more time to research their oral health issues before seeing their dentists, the dentists and the dental team must be prepared for all types of questions. Having the tools necessary to understand the latest and most significant research allows dental professionals to consistently educate themselves. However, there is no independent committee that handles the current issues facing dentistry. Using the topic of asymptomatic removal of third molars as a framework for EBD education, it can be used to help improve how schools educate their students. It is important that both the dental community and the public understand the scientific literature behind the removal of third molars because the existing practice of removing third molars without adverse symptoms is not statistically supported. Unfortunately, there is not enough evidence in favor of either side of the situation. Major databases, like PubMed, contain very little research on the asymptomatic removal of third molars, and those studies were not done recently. For EBD to be successful in dentistry, it must function in the clinical environment, but initial training in the concepts of EBD must start during pre-doctoral education. The dental practitioner still must rely on his or her own experience, but the patient must also trust his or her dentist. EBD is based on trust because it is based on the trust you have demonstrated through your skills and your usage of all available resources. If the dentist can compile pertinent scientific data and information to share with the patient and make the best decision together, then the use of EBD will be beneficial to the field of dentistry.

This study involved the use of soil and suspended growth microcosms to study the variation in groundwater denitrification rates using different substrates. Two gaseous substrates, carbon monoxide and methane, were studied and compared to a common liquid substrate, methanol. Denitrification with carbon monoxide as a substrate was achieved using an acclimated seed of mixed activated sludge and anaerobic digester sludge. Kinetic studies of denitrification using carbon monoxide suggested a strong substrate inhibition effect. The observed maximum denitrification velocity of 0.026 mg N/d-mg VSS occurred at a carbon monoxide partial pressure of 0.10 atmospheres (2.8 mg/ℓ). At higher carbon monoxide partial pressures, denitrification velocities decreased. The denitrification velocities at various carbon monoxide concentrations were described by a modified form of the Haldane substrate inhibition model. The biomass yield using carbon monoxide was 1.1 mg VSS/mg VSS, the maximum specific growth rate was 0.03 mg VSS/d-mg VSS, and the half velocity constant was 26 mg-N/ℓ. Denitrification rates using carbon monoxide as a substrate were much slower than those obtained using methanol, and the cost of carbon monoxide was much higher. Denitrification occurred readily, when methanol was provided as a substrate, in microcosms containing either a clay soil, a sandy soil, or activated sludge. Under the conditions of this study, denitrification was not achieved in clay soil or sandy soil microcosms using methane or carbon monoxide as substrates. Denitrification was not achieved using methane as a substrate with an activated sludge seed. / Ph. D.

In recent years, the United States has seen a high demand for dam rehabilitation projects as most dam infrastructure has started to reach or exceed the expected life span of 50-70 years. Rehabilitation projects can be very expensive, however, and the funding options for dam owners are limited. To raise awareness, organizations such as ASDSO and the Virginia DCR release cost estimates every few years to encourage more investment in dam infrastructure. Unfortunately, many cost estimates have been made with limited data and outdated methodologies. This research collects a new sample of cost data for Virginia dam rehabilitation projects and uses it to assess key factors for cost estimating. Factors such as height, drainage area, hazard classification, and ownership type were used to make regression models that predict the cost of addressing Virginia's non-compliant dams. This study estimates that approximately $300 million is needed to address Virginia's 98 deficient high hazard, local government owned dams and that $122 million of that estimate is need for SWCD dams alone. / Master of Science / Dam rehabilitation refers to the repair, removal, or upgrade of an existing dam structure. Rehabilitation projects are done when dams start to exceed their intended life span (approximately 50-60 years) or when policy makers change the required safety standards. The demand for dam rehabilitation has been increasing for the past several years as more and more dams are being identified as unsafe, but the available funding for rehabilitation projects is limited and competitive to obtain for dam owners. To raise awareness, dam safety agencies release cost estimates every few years to encourage government leaders and the general public to take action. However, these estimates need to be taken with caution as they are often made with limited data availability and outdated methodologies. This research collects a new sample of cost data for Virginia dam rehabilitation projects that have occurred in the last 15 years. Dam characteristics such as height, watershed size, downstream risk potential, and ownership type were used to form equations that predict the cost of addressing Virginia's non-compliant dams. This study estimates that approximately $300 million is needed to address Virginia's 98 deficient high hazard, local government owned dams and that $122 million of that estimate is need for Virginia's Soil and Water Conservation District dams alone.

The main goals of this research are to investigate the anaerobic digestibility of algae and to investigate the effects of growth media on the growth rates, nutrient removal kinetics, and extracellular polymeric substances (EPS) characteristics of wild type green algae. Anaerobic co-digestion of algae with sewage sludge is proposed to improve the digestibility of algae. It is hypothesized that the addition of sewage sludge improves the hydrolysis rate of algae, which is often the rate-limiting step for anaerobic digestion. It is also hypothesized that the composition and concentration of nutrients in growth media will affect the kinetics of nutrient removal and the content of EPS, which will influence algae flocculation and subsequent anaerobic digestion. In this research, algae collected from a local wastewater treatment plant were cultivated in synthetic medium, primary wastewater effluent and pure or diluted anaerobic sludge centrate. Light cycles and the level of CO2 addition were varied at different stages of cultivation for nutrient removal and physiochemical properties of algae. Harvested algae were then anaerobically co-digested with varying proportions of sewage sludge under mesophilic condition. Results showed that when algae were digested alone (i.e. no sludge addition) with a small amount of seed sludge, algae were poorly digested. When algae were co-digested with sewage sludge, the gas yield was improved and the gas phase (CH4 generation) was reached faster. The biogas yield of algae increased to a comparable level to that of digestion of waste sludge when 44% (by VS) of seed sludge was inoculated for digestion. The addition of sewage sludge improved the hydrolysis rate and the overall digestibility of algae. Algae grown in primary effluent, which had a balanced N/P ratio showed a higher nutrient removal efficiency. The P-limitation in sludge centrate led to lower nutrient removal efficiency and higher EPS production compared to algae grown in primary effluent, indicating that sludge centrate was a harsher medium for algae growth. In conclusion, microalgae can grow in primary effluent and anaerobic sludge centrate for nutrient removal. Anaerobic co-digestion of algae withwaste sludge was strongly recommended to enhance the biogas generation.

<p> A simplistic equilibrium, computer model was devised to simulate the removal of orthophosphates from wastewater. The components of the model were calcium, magnesium, carbonate and orthophosphate present as simple hydrated ions, ligands, acid-base dissociation products, ion pairs, ion pair complexes, ion complexes and precipitates. Data from laboratory experiments were tested in the model to determine the apparent activity products of calcite, hydroxyapatite, tricalcium phosphate and brucite. The results indicated a degree of supersaturation of hydroxyapatite between 15 to 20 orders of magnitude dependent on the aqueous species included in the calculations. The apparent pKsp values for different sets of data showed the mean ranging from 95 to 102.5 with standard deviations 2 to 5. The inclusion of the aqueous ion complexes Ca2·HPO4·CO^o 3 and Ca2·PO4·CO- 3 when calculating the apparent activity products results in a pKsp of 102.5 which varies little with pH or the presence of magnesium. The solubility of tricalcium phosphate varies more with pH than hydroxyapatite, a mean pKsp of 26.8 was calculated which compares favourably with the pKsp of 27.0 quoted in the literature. The apparent activity product of brucite was strongly dependent on pH while that of calcite was extremely variable. When hydroxyapatite precipitated, there was a minimum residual phosphate between pH 8.5 - 9.0, followed by an increase of phosphates in solution due to calcium being removed by the precipitation of calcite. Beyond pH 10, the phosphate concentration in solution decreased rapidly as there was an increase in the precipitation of hydroxyapatite coupled with a decrease of calcite. Under identical initial conditions, the precipitation of tricalcium phosphate compared to hydroxyapatite resulted in similar orthophosphate residuals. The use of the apparent activity products compared to literature solubility products results in 2 to 3 orders of magnitude greater phosphate residuals in solution.</p> / Thesis / Master of Science (MSc)

No description available.

Per- and polyfluoroalkyl substances (PFAS) are a rising topic in the field of contaminated sites around the world, with destruction of these being an area in dire need of innovation. Previous experiments of destructive character have been proven efficient using boron doped diamond electrodes (BDD) in small scale electrochemical cells. Further need for experimentation on actual site conditions is needed to further evaluate the use of this method, as well as research on alternative electrode materials to reduce the cost of remediation.  In this study, four cells containing contaminated soil were used: one with BDD electrodes, one with iron electrodes and two control cells. The iron electrodes were used to investigate if a less costly electrode material could achieve any degree of PFAS degradation. For the experiment a soil from a previous firefighting training site where firefighting foam containing high amounts of PFAS (620                     g/kg soil concentration) was used. During the first phase of the experiment a constant flow of deionized water was added to the cells containing the soil, and porewater was sampled at the in- and outflow along with the soil porewater, on a weekly basis, to evaluate the distribution of PFAS to provide information about possible degradation taking place. The extent of degradation was not quantified. However, due to differences in the molecular composition of the analysed PFAS a trend where short-chain PFAS increase throughout the experiment in the BDD cell indicated that short-chain PFAS were generated, which is an expected by-product in electrochemical oxidation of PFAS. No short-chain PFAS generation was seen in the iron electrode cell, nor was there a high amount present in the control cell leachate.  Further, leaching of PFAS was more efficient in the control cells, while PFAS in the BDD and iron electrode cell were retained or leaching was slowed down, most likely due to the electrode interaction with PFAS in porewater.Additionally a second phase where water flow through was halted and the cells were run in a batch mode was conducted to see PFAS degradation in stagnant conditions over time. In the stagnant cell in the second phase, only low PFAS concentrations in porewater were recorded while no degradation was established.  Further, fluoride analysis recorded F- concentrations in the range of    M, where the limit of detection was   M, which limited the confirmation of PFAS mineralisation in soil.  From this study insight of the difficulties with soil treatment of PFAS using electrokinetic method was highlighted, with sampling being a key factor in the accuracy of the result. For a more accurate establishment of the degradation experiments in a closed cell, with more extensive sampling throughout the entire column would be necessary. This is needed to generate a clearer picture of changes in PFAS concentration in the soil from the presumed degradation, coupled with a mass balance to provide the fate of PFAS in this type of setup.

Harmful algal blooms (HABs) can be detrimental to ecosystems, human health, and economies. The low levels of phosphorus remaining in the effluent of municipal wastewater treatment plants can contribute to HAB formation. To achieve more complete phosphorus removal, an effluent treatment method has been proposed that uses phosphorus-deprived, filamentous microalgae to quickly assimilate soluble phosphorus to low concentrations. This study investigated two parameters that influence the feasibility of such a system: (1) the biomass growth productivity of algal cultures during the phosphorus deprivation period and (2) the correlation between the duration of this period and the phosphorus uptake rate by the biomass when contacted with the water to be treated. A single strain of filamentous algae, Tribonema minus, was used. Two experiments lasting 8-9 days compared the biomass productivity of cultures of T. minus grown in phosphorus-replete and -deplete media. While no significant difference in productivity was observed between treatments, further studies should be done to confirm this finding. In addition, 39 uptake contact experiments were conducted. The soluble phosphorus uptake rate was measured for algae deprived of phosphorus for 0 to 12 days of growth. The highest observed uptake rate was 3.83 mg P/g VSS-h, during the first three hours of contact, by biomass that had been phosphorus-deprived for 12 days. The correlation between phosphorus deprivation duration and 3-h uptake rate was 0.34 mg P/g VSS-h per day of deprivation (R2 = 0.81). Additional development efforts seem justified based on these results.

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.