Le traitement des effluents et eaux usées par bioréacteurs à membranes immergées (BAMI) permet d'obtenir une haute qualité de perméat par une dégradation biologique et une séparation physique. Néanmoins, le procédé de filtration est limité par l'influence de facteurs très complexes, en particulier le colmatage de la membrane. Le but du travail est de développer des modèles dynamiques et de simuler le procédé de filtration dans les BAMI. Le développement et la simulation des modèles ont été ciblés sur la description des rapports existants entre les variables les plus importantes du système, comme la pression transmembranaire (PTM), les matières en suspension (MES), les substances polymériques extracellulaires (SPE) et l'influence sur l'évolution du colmatage d'une aération syncopée, injectée à la surface de membrane, et sa synchronisation avec une filtration intermittente. Le modèle et les études d'optimisation du système ont été validé par voie expérimentale. / This thesis studies a submerged membrane bioreactor (MBR) technology that is used to treat effluents. We present in detail the modeling of this process, the validation of developed models, and the results of simulation and optimization carried out with the above mentioned models. The new contributions to scientific knowledge of this work are the following: - A new dynamic model that integrates for such systems, many of the variables and the main phenomena occurring during the process of filtration in MBR wastewater treatment. That constitutes an original contribution to the analysis and development of this technology. – The simulation allows to achieve the quantification of the influence and effect of aeration on the process (membranes fouling) and the influence of the sequencing of the filtration and coarse bubbles aeration cycles. All that takes into account the behavior of biomass, the generation of exopolymeric substances and inlet characteristics. The results provided by the model are validated by comparison with experimental results. – An optimization of MBR operating conditions using the experimental design for simulation, is reported based on the results obtained using the developed models / En la presente tesis se reflejan los estudios realizados en un biorreactor con membrana sumergida, tecnología que se utiliza para el tratamiento de efluentes residuales. Se presentan de forma detallada la modelación de este proceso, la validación de los modelos desarrollados, así como los resultados de la simulación y optimización realizados con los modelos. Entre los nuevos aportes al conocimiento científico del trabajo se encuentran los siguientes: - Un nuevo modelo dinámico que integra por primera vez, para estos sistemas, muchas de las variables y los principales fenómenos que ocurren durante el proceso de filtración y tratamiento de las aguas residuales utilizando los BMS. Lo cual constituye un aporte novedoso para el análisis y desarrollo de esta tecnología. - Se logró por primera vez cuantificar mediante simulación la influencia y el efecto de la aireación sobre el proceso de colmatación de las membranas, así como la influencia de la sincronización de los ciclos de filtración y aireación de burbujas gruesas. Todo esto tomando en cuenta el comportamiento de la biomasa, la generación de sustancias colmatantes y las características de la alimentación. Se validaron los resultados que ofrece el modelo mediante la comparación con resultados experimentales. - Se reporta por primera vez la optimización de las condiciones operacionales de un sistema BMS utilizando el diseño de experimento para la simulación, partiendo de los resultados obtenidos utilizando los modelos desarrollados

Microplastic (MP) pollution is ubiquitous in the aquatic environment. Though their properties are known to vary considerably, these particles are typically 1–5,000 μm in size and irregular in shape. Research suggests that MPs pose a significant hazard to aquatic ecosystems, lead to negative economic consequences, and may cause adverse human health effects. The effluents of municipal wastewater treatment plants (WWTPs) comprise a significant source of MPs, containing < 1 MP/L to > 440 MPs/L. Pursuant to the large volumes of wastewater processed, estimated daily effluxes can exceed one billion MPs/day in some WWTPs. Membrane technologies, like those used in some tertiary wastewater treatment applications, appear well-positioned to mitigate releases of MPs. However, research directly characterizing the performance of membranes in these applications is lacking. The studies in this work address this knowledge gap. To this end, irregularly-shaped MPs were produced in a novel milling/sieving process. Ultrafiltration and microfiltration membranes were challenged to these MPs suspended in secondary effluent wastewater to elucidate their fouling behaviour under realistic solution conditions. Subsequently, MPs milled/sieved from a fluorescently-labelled plastic feedstock were utilized in microfiltration experiments. Bulk MP concentrations in samples were easily measured using a plate reader to quantify MP rejection. Improving upon this technique, a new protocol involving a flow cytometer was developed, enabling the identification of individual fluorescent MPs in filtration samples, even when complex solutions chemistries were used. A culminating investigation was performed to bridge a gap in the literature between studies considering small-scale laboratory filtration phenomena and observations of large-scale WWTPs. Thus, the performance of a hollow fiber crossflow microfiltration module was evaluated in the filtration of wastewater containing MPs. Overall findings suggest that incidences of fouling by MPs can be managed via periodic cleaning processes, and the well-informed selection/operation of membrane technologies can contribute to high MP removal efficiencies (> 99%) in tertiary wastewater applications. / Thesis / Doctor of Philosophy (PhD) / The term "microplastics" (MPs) is used to describe microscopic plastic particles. Recent investigations have reported these MPs in lakes, rivers, and oceans across the globe. These reports are concerning as other studies demonstrate that MP pollution can be hazardous to aquatic life, yet the potential effects of MPs on human health remain largely unknown. Many MPs originate from municipal wastewater treatment plants (WWTPs) which discharge large numbers of these particles into the aquatic environment. Researchers often recommend the use of membranes as a barrier to prevent MPs from leaving in the final treated wastewater. This work seeks to assess that recommendation. Assessments of the effectiveness of membranes at withholding MP particles in wastewater are performed over various conditions. The propensity of MPs to interfere with the desired output of treated wastewater is also measured. Overall, findings indicate that carefully designed and operated membranes processes can be well-suited to this application.

Yes / Reverse Osmosis (RO) is widely used for separating organic and inorganic pollutants in wastewater. In this research, the one-dimensional steady state model of a spiral wound RO for the removal of phenol from wastewater, was simulated using gPROMS software to identify optimal design and operating parameters. The design parameters included the membrane length, width and feed spacer channel and operating conditions included temperature and pressure of the RO process. The optimal design parameters were able to maximise the removal of phenol from wastewater. The simulation results showed that the removal of phenol from wastewater was significantly influenced by the combination of membrane width, operating pressure, and feed temperature. The four main parameters (permeate concentration, solute flow, solute rejection, and water flux) that govern the performance of a reverse osmosis membrane were found to be influenced by the design and operating conditions.

A Thesis Submitted to the School of Graduate Studies in Partial Fulfilment of the Requirements for the Degree of Master of Science. / Onsite wastewater treatment systems may be improved by altering the design and environmental variables that affect microbial community composition. However, the two most common methods of examining microbial composition through metagenomic sequencing (16S and shotgun sequencing) produce different taxonomic identification results according to microbial community composition and the analytical methods in use. To identify discrepancies between these two sequencing methods, we analyzed the effect of environmental and tank design variables on onsite-wastewater treatment system microbial communities sequenced using both 16S and shotgun sequencing. Shotgun and 16S sequencing produced different results when examining genera-level taxonomic richness, quantifying the effect of system design and environmental variables on community similarity, and identifying differentially abundant taxa between system types. Results were consistent when subjectively examining patterns of community similarity and when examining genera-level taxonomic diversity above 0.1% relative abundance. Identifying methods that produce similar results between 16S and shotgun sequencing supports the reliable analysis of and optimization of OWTS processes. / Thesis / Master of Science (MSc) / Onsite-wastewater treatments systems such as household septic tanks are vital tools for managing wastewater. However, the microbial ecosystem which digests waste within septic tanks contains unknown interactions that can alter the rate of waste digestion. We used two DNA sequencing methods to assess how microbial communities within septic tanks responded to the tank design and surrounding environment. We then compared results produced by the two sequencing methods. The response of microbial communities to tank design and the environment differed between the two methods. However, the two methods both indicated that one system design produced a more variable microbial community.

This thesis explores the development of direct electrochemical reduction as a means of providing primary treatment of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a manufacturing process waste stream. An industrial process wastewater laden with RDX was successfully treated in small batch reactors. Reaction kinetics were used to design a proof of concept bench scale flow reactor that utilized parallel packed electrode plates. Following successful testing of this reactor, a pilot scale packed electrode flow reactor was built. The reactor performance as a function of residence time was fit by a first order decay equation. Greater than 97% reduction of RDX in a process wastewater was observed at a reactor residence time of 27 minutes. The work presented herein was successful in creating an electrochemical treatment system capable of removing RDX from an industrial process waste stream with no chemical addition, and without creating an additional hazardous waste stream.

No description available.

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.

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

Wastewater treatment plants (WWTPs) receive a confluence of sewage containing antibiotics, antibiotic resistant bacteria, antibiotic resistance genes (ARGs), and pathogens, thus serving as key point of interest for the surveillance of antibiotic resistance (AR) dissemination. This thesis advances knowledge about the fate of AR indicators throughout treatment and reuse. The field study informs approaches for monitoring AR at a WWTP by characterizing the resistome (i.e., full profile of ARGs) and microbiome across eight sampling events via metagenomic sequencing, complemented by antibiotic data. The WWTP significantly reduced the total load of ARGs and antibiotics, although correlations between ARGs and antibiotics were generally weak. Quantitative polymerase chain reaction was applied to validate the quantitative capacity of metagenomics, whereby we found strong correlations. The influent and effluent to the WWTP were remarkably stable with time, providing further insight into the sampling frequency necessary for adequate surveillance. The laboratory study examined the effects of commonly applied disinfection processes (chlorination, chloramination, and ultraviolet irradiation [UV]) on the inactivation of antibiotic resistant pathogens and corresponding susceptible pathogens in recycled and potable water. Further, we evaluated their regrowth following disinfection by simulating distribution. Acinetobacter baumannii, an environmental opportunistic pathogen, regrew especially well following UV disinfection, although not when a disinfectant residual was present. Enterococcus faecium, a fecal pathogen, did not regrow following any disinfection process. There were no significant differences between water types. The findings of this study emphasize a need to move beyond the framework of assessing treatment efficacy based on the attenuation of fecal pathogens. / Master of Science / Wastewater treatment plants (WWTPs) have traditionally been designed and further enhanced to minimize environmental contamination caused by solid waste, fecal pathogens, nutrients (e.g., nitrogen), and organic matter. However, treatment has not been optimized to remove the contaminants of emerging concern (CECs) investigated in this thesis: antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs), and antibiotics. WWTPs are key point of interest for local and global surveillance of antibiotic resistance as they can receive the aforementioned CECs (via human excretion or improper disposal) from various sources (e.g., residences, hospitals). Antibiotic resistant bacteria have caused 2.8 million infections and subsequently 35,000 deaths in the United States each year. Considering treated wastewater can serve as a route of exposure for humans, potential spread of antibiotic resistance by WWTPs is of high priority to mitigate from a public health perspective. In the first study utilizing a technology to assess the full complement of ARGs in a given sample, we observed that the total load of ARGs was removed by approximately 50% across wastewater treatment, on average; total antibiotic load exhibited a similar reduction. The second study demonstrated that antibiotic resistant environmental opportunistic pathogen (i.e., pathogens which take advantage of the "opportunity" to infect an immunocompromised host, especially thriving in low nutrient engineered systems), Acinetobacter baumannii, possesses the ability to regrow following disinfection in the absence of a disinfectant residual. In contrast, antibiotic resistant Enterococcus faecium, an opportunistic pathogen of fecal origin, was successfully inactivated and unable to regrow. The findings of this study emphasize a need to move beyond the framework of assessing treatment efficacy based on the attenuation of fecal pathogens.

In natural waters, high concentrations of ammonia are toxic to fish, and the oxidation of ammonia to nitrate (NO₃-) consumes large quantities of dissolved oxygen. The influent to municipal wastewater treatment plants in the United States typically contains approximately 40 mg/L of ammonia nitrogen (NH₃₋ N). Almost all of this ammonia must be removed in a wastewater treatment process before the effluent is discharged to the natural environment. This dramatic decrease is accomplished by the aerobic biological process of nitrification, in which ammonia is oxidized to nitrate Biological denitrification is an anoxic biological process in which nitrate (NO₃-) is reduced to nitrogen gas (N₂). Denitrification can increase the alkalinity in activated sludge aeration basins and decrease the concentration of filamentous organisms. The staff at the City of Austin Water Utility decided to implement a denitrification system at Walnut Creek Wastewater Treatment Plant to control filamentous organisms and increase the alkalinity within the aeration basins. The denitrification configuration that the staff implemented was unconventional because no structural changes were made to the aeration basins to encourage denitrification. However, the system functioned well and allowed operators to turn off one of the two air blowers, which saves the plant a significant amount of energy. The current operation has occasional problems, where the alkalinity in the aeration basin decreases or the effluent ammonia increases. When the alkalinity decreases to the point where the pH drops to near 6.0, operators are forced to add chemicals to increase the alkalinity. When the effluent ammonia increases to near the permitted concentration (2.0 mg NH₃-N/L),operators are forced to turn back on the second blower which eliminates the anoxic zone. These problems occur most often during the winter, when the wastewater is the coldest. The wastewater temperature at Walnut Creek varies from a high of 30°C during the summer to a low of 18°C during the winter. The goal of this research was the identification of ways to make the operation more robust which would prevent the need for chemical addition and minimize the use of the second blower. Laboratory-scale reactors were operated to assess possible improvements that could be made to the operation and configuration of the denitrification system at Walnut Creek. The data observed in the laboratory scale experiments showed that the population of denitrifying bacteria limits denitrification and is especially important during the winter. Increasing the solids retention time to 20 days appeared to be the best way to increase the population of denitrifying bacteria and improve denitrification. Improvements can also be made by increasing the volume of the anoxic zone. Increasing the volume of wastewater and biomass recycled will most likely not benefit denitrification until other improvements have been made. Recommendations to the City of Austin Water Utility include the following: 1) increase the solids retention time at Walnut Creek, 2) Increase the volume of the anoxic zone, 3) Separate the anoxic zone from the aerobic section of each aeration basin, 4) During the winter, operate the flow equalization basins to reduce the dissolved oxygen entering the anoxic zone, 5) Continually mix some of the effluent from the aeration basins with the primary effluent in the flow equalization basins. / text