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Contaminated stormwater discharge is a major concern in the United States due to a steady increase of harmful pollutants entering fresh water sources. The many congressional mandates that require local governments to reduce the impact of storm water discharge on the natural ecology have greatly increased the need for economically and environmentally viable solutions to pollution reduction. One such solution is that of constructed wetlands. Previous research conducted at the Sustainable Bio-products Department at Mississippi State University demonstrated the feasibility of kenaf fiber and wood shavings to remove toxins and crude oil from the bio-oil process water. This study proposes to amend contaminated storm water runoff from a biomass to bio-oil conversion facility through a simulated constructed wetland. The constructed wetlands were contaminated with varying dilution levels of bio-oil process water in a series of six phases. It was hypothesized that the contaminated rainwater can be remediated by constructed wetlands and safely released back into the native waterways. This study concluded that there was a significant decrease in biological oxygen demand (BOD) and micro-toxicity over a ten day cycle within the constructed wetlands for the lower levels of contaminated stormwater. A comparative screen of the bacterial community within the wetlands during the contamination process showed a similar trend in species richness and composition for the first three Phases of contamination. There was a shift in richness and diversity for the final three Phases of contamination after ten days within the constructed wetlands. The constructed wetlands were successful at lowering BOD and toxicity levels and achieving permissible pH levels when the concentration of contaminated stormwater was less than or equal to 400x dilution. Much of the BOD reduction was due to volatilization of the contaminated wastewater. When the concentration of contaminated water exceeded 300x dilution, the constructed wetland were only successful at achieving permissible pH discharge levels. Better results may be achievable with longer residence time in the wetlands.

<p> Laboratory and field measurements were combined with theory in developing models for the various wastewater treatment processes. Some assumptions were made, both in an attempt to simplify the complex mechanisms encountered and to explain known experiences and observations. </p> <p> Models for a primary settling tank, a secondary settling tank, a generalized aerobic biological sludge treatment scheme, an anaerobic digestion system and several other unit processes have been developed. The generalized aerobic biological sludge treatment scheme is an attempt to describe in one physical package, all the various activated sludge process modifications. </p> <p> The executive system used is GEMCS · together with its library of subroutines, such as CONTLl, SEPAOl, JUNCOl and SETSPI, some of which have been modified slightly. </p> <p> The models have been tested on the Drury Lane and the Skyway, Burlington, Sewage Treatment Plants, and have been found to agree very well with plant data. The former has a conventional activated sludge process, whilst the latter employs the extended aeration modification. </p> <p> An inter-active version has been developed, which requires the minimum knowledge of GEMCS for its use. This can be applied as a training and teaching tool for plant operators and students in the field. </p> / Thesis / Master of Engineering (MEngr)

<p> This work examines the feasibility of continuous biological nitrification and denitrification for nitrogen removal from municipal wastewater. Pilot plant'studies were conducted using a rotating biological contactor (RBC) for nitrification and upflow packed columns for denitrification. Of primary interest were the effects of temperature on the systems. </p> <P> It was found that an Arrhenius model adequately described nitrification rates measured over a range of temperatures from 7 degrees C to 250 degrees C. Direct comparison of the Arrhenius Activation Energies determined for the RBC and a two stage activated sludge system with intermediate clarification showed that nitrification in the RBC was less temperature sensitive than in the activated sludge process. At 10 degrees C, roughly 20 mg/hr·m^2 (0.10 lb/day•1000 ft^2 ) of ammonia as nitrogen was removed from the system. </p> <p> The rate of denitrification in the packed column reactors displayed great variability. The temperature dependency of the data could not be characterized by an Arrhenius model or any other simple relationship. Although significant nitrate removal was observed at all temperatures between 5°C and 25°C, severe short circuiting due to solids accumulation tended to limit minimum nitrate effluent concentrations to 1 or 2 mg N03^-N/~. </p> / Thesis / Master of Engineering (MEngr)

Yes / To date, mixing design practice in anaerobic digestion has focussed on biogas production, but no adequate consideration has been given to energy efficiency. A coherent, comprehensive and generalized strategy based on computational fluid dynamics (CFD) modelling is proposed to improve mixing efficiency of a full-scale, unconfined gas-mixed digester for wastewater treatment. The model consists of an Euler-Lagrange (EL) model where biogas bubbles are modelled as the Eulerian dispersed phase, and non-Newtonian sludge as the Lagrangian continuous phase. Robustness tests show that mixing predictions are independent of bubble size. The CFD strategy comprises the assessment of different mixing geometries and a range of input gas flow rates. Quantitative results show that simple retrofitting measures are able to achieve a significant improvement in the degree of mixing with reduced mixing times, and consequently recommendations for best mixing geometry and gas flow rate are given. A generalization to a generic digester is discussed in a form that is readily usable by professionals and consultants.

Airborne microorganisms, such as bacteria, viruses and fungi, are abundant in the natural and built environments. This research encompasses two studies on virus aerosolization and transport in the built environment and the subsequent implications for human health. In the first study, we quantified the impact of a barrier on the spatial distribution of different-sized particles released by speaking in a poorly ventilated room. The room was outfitted with 108 passive sampling sites. The barrier resulted in an increase in 0.5 µm particles deposited on the source-side of the barrier and an increase in 0.5 µm particles at other locations 4-6 m from the source. The barrier had minor impacts on the distribution of 1, 6, 10 and 20 µm particles. The results from this study indicated that barriers may not serve as adequate protection to others in the room, depending on their locations relative to the barrier and the timescale of exposure. In the second study, we reviewed the applications of next-generation sequencing for viruses in water environments. We also characterized the occurrence of two viruses (crAssphage and SARS-CoV-2) from a local wastewater treatment plant (WWTP) in both water and air samples at two locations within the WWTP (influent and aeration basin). We found that crAssphage, a fecal indicator, was quantifiable in most air and water samples, but was not detected in control samples. SARS-CoV-2 N2 RNA was detected in a fraction of the water and air samples but was present in the control water samples, so results for this virus are confounded by laboratory contamination. We also found that there was no correlation between airborne and waterborne SARS-CoV-2 concentrations at the WWTP. A quantitative microbial risk assessment model was constructed to determine inhalation risks associated with airborne SARS-CoV-2 for WWTP operators. The probability of infection ranged from about 2.4 x 10-4 to 5.6 x 10-8 and was heavily dependent on exposure time, airborne concentration and other parameters. / Doctor of Philosophy / Airborne microorganisms, such as bacteria, viruses and fungi, are abundant in the natural and built environments. This research encompassed two studies that evaluated the impact of viruses in the built environment on public health. The first study investigated whether a barrier, like Plexiglas, could protect people from another person's exhaled particles in a poorly ventilated room. The barrier resulted in an increase in the smallest particles (0.5 µm) on the same side of the barrier as the source and an increase in these particles at other locations 4-6 m from the source, indicating that individual exposure depends on their location relative to the barrier. The barrier had minor impacts on larger particles (1, 6, 10, and 20 µm). The second study focused on viruses at wastewater treatment plants (WWTPs). As part of this study, we reviewed how one can use knowledge about the DNA and RNA of viruses in water and wastewater. We also measured the amount of two viruses (crAssphage and SARS-CoV-2) in wastewater and in air surrounding the WWTP. We detected crAssphage, a virus that infects bacteria and a marker for human activity, in most wastewater and air samples. We also detected SARS-CoV-2 in some wastewater and air samples, but this virus was also present in some control samples, so laboratory contamination was an issue. Using the concentrations of airborne SARS-CoV-2, we constructed a computational model to estimate the risk of infection for SARS-CoV-2 inhalation for WWTP employees. Our calculations indicated that the risk of infection ranged from 2.4 x 10-4 to 5.6 x 10-8 and heavily depended on parameters such as exposure time and airborne SARS-CoV-2 concentrations.

Sixteen small scale Subsurface vegetated beds (SVB) were installed down slope of the residence at the Whitethorne Planation (WP) site. Treatments included three detention times (2.6, 3.9, and 5.9 days), two recirculation ratios (0 and 0.5), and two plant species [woolgrass (<i>Scirpus cyperinus</i>) and cattail (<i>Typha latifolia</i>)]. Twelve larger scale SVBs were constructed at the Powell River Project (PRP) site, Wise County, VA. Treatment consisted of three detention times (4, 8, 12 days) with the same plant species (cattail and woolgrass). At the WP site, pollutant removal incresed with detention time for 5-day biochemical oxygen demand (BOD₅), total Kjeldahl nitrogen (TKN), ammonium (NH₄-N), phosphates (PO₄³⁻-P), redox potential (Eh), and total dissolved solids (IDS). The pollutant removal rates, based on 23 data sets, were: BOD₅ (54-70%); NH₄⁺-N (30-61%); TKN (33-52%); PO₄³⁻-P (7-28%); fecal coliforms (FC) (>99%) and coliphages (>95%). Recirculation appeared to have no apparent benefit. There were no differences in P, S and secondary and trace metals concentrations in the SVBs planted to cattail and woolgrass. Plants could remove 2 -10% of the total N applied and 13-57% of the total P applied to the SVBs if harvested once a year during the growing season. At the PRP site, differences were observed among the detention times for BOD₅, TKN, NH₄-N, PO₄-P, TDS, pH, EC and Eh. The pollutant removal percentages were: FC (>99%); BOD₅ (30-75%); NH₄-N (27-88%); TKN (27-81%); PO₄³⁻-P (24-46%); and TDS (12-73%). Samples collected from shallow wastewater column exhibited a higher level of treatment. There were no differences in FC, BOD₅, TKN and NH₄⁺-N concentrations between s VB s planted to cattail and woolgrass, and there were no differences in tissue N content between cattail and woolgrass at both sites. The average NH₃ volatilization rate was 236 mg N/m²/day, and accounted for 7-37% of total N applied to the SVBs. Average measured denitrification rates ranged from 3.87 to 6.69 mg N₂O /m²/ h, and accounted for 2-17% of total N applied. / Ph. D.

The performance of Captor media integration into the aerobic zone of an activated sludge wastewater treatment system operated at low MCRTs was evaluated using a pilot scale Virginia Initiative Project (VIP) process. Two separate trains were operated, one with Captor media incorporated into the aerobic zone of the system, referred to as an Integrated Fixed Film Activated Sludge (IF AS) system, and the other as a control system, i.e., with no media in the aerobic reactors. The wastewater used for this research was pumped from a main municipal sewer of the Blacksburg-VPI Sanitation Authority Collection System. The TKN of the wastewater was supplemented by the addition of urea to maintain the influent ammonia concentration around 55 mg/L as nitrogen. Sodium acetate was added to maintain the influent COD around 450 mg/L and Sodium bicarbonate was added to maintain the pH in the aerobic zone around 7. The system was operated at MCRTs of 1.7, 1.0 and 0.3 days with the operating temperature around 12 C. / Master of Science

Many utility asset management programs have been developed following the U.S. Environmental Protection Agency (EPA) core definition of maintaining a level of service at the lowest life cycle cost. Most utilities, however, only incorporate performance measures into their asset management plans. A holistic approach to asset management is more beneficial because it takes into account the short and long term goals of the utility and can provide better service socially, economically, and environmentally. An analysis of the Town of Blacksburg wastewater utility's practices and data collection was performed using a holistic asset management framework developed at Virginia Tech. This theoretical framework supports the three key aspects of asset management: performance, sustainability, and resilience. Where gaps were identified, recommendations were made as to what practices, goals, and data the Town can add to their current plan so that their program is more holistic. Research has shown that many utilities have trouble adapting to asset management plans because job roles and responsibilities change and are often not well defined. To help the Town of Blacksburg adapt to their new asset management plan with performance, sustainability and resiliency goals, a work process flow was designed. A work process flow allows for visible changes in job responsibility to be more easily recognized as well as allow for future changes to be made. / Master of Science

As one of the largest and most productive estuaries in the United States, the Chesapeake Bay is a great economic, ecological, and cultural asset to the Mid-Atlantic region. Excess nitrogen and phosphorus discharge, however, has contributed to reduced levels of dissolved oxygen in various locations throughout the Bay. In 2010, the EPA developed a Total Maximum Daily Load (TMDL) for the entire watershed that established nutrient reduction targets to achieve Bay water quality objectives. The TMDL required states in the Chesapeake Bay watershed to create implementation plans to meet nutrient reductions. Maryland and Virginia specifically established stringent point source regulatory policies designed to meet point source reduction targets. Point source control programs created financial incentives for reducing nutrient discharge beyond regulatory requirements. This thesis will examine the extent to which Maryland and Virginia wastewater treatment plants undertake operational improvements to increase nutrient removal in response to state program incentives. Through quantitative and qualitative analysis, this thesis found evidence of lowered nitrogen discharges in response to financial incentives presented by each states point source control programs at municipal wastewater treatment plants. Maryland achieves modest improvements at a subset of advanced treatment WWTPs as a result of financial incentives presented by the state's public subsidy program. Although Virginia advanced treatment plants operating within a nutrient trading program have little incentive to over-comply, there is some evidence of operational improvements at less advanced nitrogen removal plants / Master of Science