Aquarium biofilters are designed to promote the growth and activity of nitrifying microorganisms, which are primarily responsible for the removal of toxic nitrogen-cycle intermediates. Ammonia is a natural waste product excreted by fish that is lethal to aquatic life at relatively low concentrations. Ammonia-oxidizing archaea (AOA) outnumber ammonia-oxidizing bacteria (AOB) in biofilters of mature freshwater aquaria with low-ammonia conditions. However, no study has investigated the early establishment of AOA and AOB within biofilter communities, especially when aquarium ammonia concentrations are elevated. My thesis research investigated the relative abundance of AOA and AOB in freshwater aquarium biofilters through early aquarium establishment. AOA and AOB genes were detected in DNA extracts from the biofilters of 14 start-up freshwater aquaria with increasing fish biomass loads (Experiment 1), as well as from 12 biofilters of start-up aquaria treated with AOA and AOB supplements (Experiment 2). In start-up aquaria, early ammonia concentrations increased with fish biomass, and AOB amoA genes were strongly detected over AOA marker genes in all filters without initial AOA inoculation. Inoculation of AOA-dominated supplements into newly established biofilters improved early ammonia oxidation rates in comparison to filters supplemented with AOB or those lacking supplements. Inoculated AOA thrived in filter biofilm during and beyond stabilization of low-ammonia conditions in aquaria. Microbial activity experiments demonstrated that AOA were present and active in the biofilters eight months after inoculation, when aquaria were fully established. In addition, AOB and AOA populations were monitored in new aquaria in three unregulated home environments. Thaumarchaeal 16S rRNA genes were detected in all aquarium filters within one month of aquarium development. In one filter, AOA were the only ammonia-oxidizers detected in the biofilm during aquarium development, suggesting that AOA were the sole contributors to nitrification in this aquarium. The results from these experiments suggest that AOA may be key players in early aquarium nitrification once introduced into the aquarium environment. Further, this research provides insight into the ecology of AOB and AOA in engineered freshwater environments

Soluble manganese (Mn) presents a significant treatment challenge to many water utilities, causing aesthetic and operational concerns. Surface water treatment plants using ozonation followed by biofiltration are unable to apply free chlorine across the filter, a method used by many utilities for soluble Mn control. These facilities are vulnerable to periodic problems of elevated Mn in the finished water. Manganese-oxidizing bacteria (MOB) readily oxidize Mn in groundwater treatment applications, which normally involve pH values above 7.0.  However, the ability of MOB to facilitate Mn oxidation under lower pH conditions (6.2--6.3) often employed to optimize organics removal has not been demonstrated. Laboratory-scale biofilters were operated to evaluate the ability of MOB to accomplish soluble Mn control at a range of pH (6.3--7.3).  The biofilters were able to oxidize Mn at a pH as low as 6.3 at greater than 98% removal.  Ozonation by-product removal was also greater than 90% in all filter columns. Stress studies indicated that well-acclimated MOB can withstand variations in Mn concentration, hydraulic loading rate, and temperature typically found at surface water treatment plants, at least for relatively short (1-2 days) periods of time. Pilot studies demonstrated that there are unknown factors that affect MOB acclimation, and MOB may be present in full-scale biofilters already. MOB are difficult to identify with current biological analysis techniques and comprise small percentages of the total microbial population. MOB have demonstrated potential for use in surface water treatment plants, but further research is needed before this application is fully feasible. / Master of Science

No description available.

Nine recirculating systems at the Virginia Tech Aquaculture Center were placed on line and stocked with yellow perch, <I>Perca flavescens</I>, fingerlings. Fish were stocked at a density of approximately 455 fish m³. Biofilter types were the only factor differing among system designs and were an upflow pulsed bed bead filter, packed tower trickling filter and a rotating biological contactor (RBC). After stocking, systems were allowed to acclimate using ammonia excreted by the yellow perch. Following acclimation, a comparative analysis on biofilter performance began. To evaluate filter performance, water quality parameters tested were temperature (°C), pH, dissolved oxygen (DO), total ammonia-nitrogen (TAN), nitrite-nitrogen (NO₂⁻-N), nitrate-nitrogen (NO₃⁻-N), alkalinity (as CaCO₃), water hardness (as CaCO₃), carbonaceous biochemical oxygen demand (cBOD₃), dissolved organic carbon (DOC), and total suspended solids (TSS). Basic water quality analysis encompassed samples drawn at 8 AM. TAN mass removal analysis encompassed water quality samples drawn at 8 AM and over 24 hours. Higher TAN mass removal rates were achieved in trickling and RBC filters than in bead filters for 8 AM (0.037, 0.14, and 0.004 g/m²/d, respectively) and diurnal sample periods. Analysis of areas under mass removal curves depicted RBC filters as surface area limited. Trickling filters proved most effective at carbon dioxide stripping and pH maintenance and also effectively removed TSS from the culture water. The study did not show filter type as having a significant effect on median organic water quality parameter values. / Master of Science

Esta pesquisa propôs o desenvolvimento de um sistema de biofiltros submersos, modificados com base na configuração de filtros de pedra, visando o pós-tratamento do efluente de lagoas de estabilização, inicialmente para a remoção de algas. A modificação consiste na variação das alturas da camada filtrante e na colocação de tampa na superfície do BS, evitando o acesso da luz. O esgoto tratado captado na lagoa de maturação foi feito em duas profundidades &#8211; a 60 cm de profundidade da superfície da lagoa (denominada zona superficial) e a 180 cm de profundidade da superfície da lagoa (denominada zona intermediárias). O experimento foi composto por 8 BS sendo 4 BS alimentados pelo esgoto captado na zona superficial (60 cm) e outros 4 BS alimentados pela esgoto captado na zona intermediária (180 cm). Foi utilizado, como recheio dos biofiltros submersos, pedra brita nº 3, nas seguintes alturas de camada filtrante: 50 cm, 100 cm, 150 cm e 200 cm, tendo por objetivo avaliar a influência deste fator sobre a eficiência de remoção de algas mediante análise de Clorofila a, e outras 16 variáveis de qualidade associadas neste estudo. Concluiu-se que a extração a partir da zona superficial da lagoa de maturação, e uma profundidade de leito entre 150 cm e 200 cm, foram os parâmetros operacionais que levaram a um melhor desempenho global dos biofiltros submersos modificados, e mais especificamente quanto às seguintes variáveis: Clorofila a, DQO (Demanda Química de Oxigênio), DBO (Demanda Bioquímica de Oxigênio) e sólidos totais. / This research proposed the development of a submerged bio filters system, modified based in rock filters configuration, aiming the post treatment of the effluent of stabilization lagoons, for algae removal first. The modification consists invariance of the heights of the filter layer and the cover placed on the surface of the BS, preventing access of light. The treated sewage captured in the maturation lagoon was made at two depths &#8211; at 60cm depth of the lagoon surface (called superficial zone) and at 180cm depth of the lagoon surface (called intermediary zone). The experiment consisted of 8 BS, with 4 BS being fed by sewage captured in the superficial zone (60 cm) and other 4 BS fed by sewage captured in the intermediary zone (180 cm). It was used, as a stuff of submerged biofilters, rock number three, at the following heights of filtering layers: 50 cm, 100 cm, 150 cm e 200 cm, aiming to evaluate the influence of this factor over algae removal efficiency towards chlorophyll a, and other 16 quality variables associated in this study. It was concluded that the collecting from superficial zone of the maturation lagoon, and a layer depth between 150 cm e 200 cm, were the operational parameters that lead to a better overall performance of modified submerged biofilters, and more particularly to the following variables: Chlorophyll a, COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand) and total solids.

Esta pesquisa propôs o desenvolvimento de um sistema de biofiltros submersos, modificados com base na configuração de filtros de pedra, visando o pós-tratamento do efluente de lagoas de estabilização, inicialmente para a remoção de algas. A modificação consiste na variação das alturas da camada filtrante e na colocação de tampa na superfície do BS, evitando o acesso da luz. O esgoto tratado captado na lagoa de maturação foi feito em duas profundidades &#8211; a 60 cm de profundidade da superfície da lagoa (denominada zona superficial) e a 180 cm de profundidade da superfície da lagoa (denominada zona intermediárias). O experimento foi composto por 8 BS sendo 4 BS alimentados pelo esgoto captado na zona superficial (60 cm) e outros 4 BS alimentados pela esgoto captado na zona intermediária (180 cm). Foi utilizado, como recheio dos biofiltros submersos, pedra brita nº 3, nas seguintes alturas de camada filtrante: 50 cm, 100 cm, 150 cm e 200 cm, tendo por objetivo avaliar a influência deste fator sobre a eficiência de remoção de algas mediante análise de Clorofila a, e outras 16 variáveis de qualidade associadas neste estudo. Concluiu-se que a extração a partir da zona superficial da lagoa de maturação, e uma profundidade de leito entre 150 cm e 200 cm, foram os parâmetros operacionais que levaram a um melhor desempenho global dos biofiltros submersos modificados, e mais especificamente quanto às seguintes variáveis: Clorofila a, DQO (Demanda Química de Oxigênio), DBO (Demanda Bioquímica de Oxigênio) e sólidos totais. / This research proposed the development of a submerged bio filters system, modified based in rock filters configuration, aiming the post treatment of the effluent of stabilization lagoons, for algae removal first. The modification consists invariance of the heights of the filter layer and the cover placed on the surface of the BS, preventing access of light. The treated sewage captured in the maturation lagoon was made at two depths &#8211; at 60cm depth of the lagoon surface (called superficial zone) and at 180cm depth of the lagoon surface (called intermediary zone). The experiment consisted of 8 BS, with 4 BS being fed by sewage captured in the superficial zone (60 cm) and other 4 BS fed by sewage captured in the intermediary zone (180 cm). It was used, as a stuff of submerged biofilters, rock number three, at the following heights of filtering layers: 50 cm, 100 cm, 150 cm e 200 cm, aiming to evaluate the influence of this factor over algae removal efficiency towards chlorophyll a, and other 16 quality variables associated in this study. It was concluded that the collecting from superficial zone of the maturation lagoon, and a layer depth between 150 cm e 200 cm, were the operational parameters that lead to a better overall performance of modified submerged biofilters, and more particularly to the following variables: Chlorophyll a, COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand) and total solids.

Gas phase biofilters are used for controlling odors from animal facilities. Some characteristics can affect their performance and moisture content is one very important. A methodology for controlling and measuring moisture content is required to optimize these systems. An experiment was conducted to determine the appropriate placement of a set of soaker hoses 1.2 m in length for water application. It was found that the soaker hose installed in the lower region of the biofilter coupled with appropriate and timely application of water was able to minimize drying of the compost. Thermal conductance proved to be a reliable indicator for measuring the moisture content. Biofilters using the soaker hoses together with the thermal conductance as a media moisture sensor were able to maintain moisture content above 30% w.b. which provided sufficient water for microbial activity and ammonia abatement. A characterization of the ammonia and nitrous oxide concentrations was performed in order to compare the behavior of the gases when water was applied versus no water addition. These analyses revealed that the overall performance was not significantly different between treatments. But a more detailed assessment inside the biofilter media is performed; it is possible to identify different processes taking place.

.Le transport de soluté en présence de biofilms en milieux poreux est un problème rencontré dans de nombreuses applications industrielles (biofiltration des eaux usées et traitement de polluants atmosphériques notamment). En termes de modélisation, l'interaction entre biologie, hydrodynamique et chimie reste difficile à comprendre aux échelles les plus fines: cela a conduit à une large utilisation de modèles macroscopiques, plus simple à manipuler. Cependant, la question consiste à écrire des modèles macroscopiques suffisamment complexes pour prendre en compte les processus pertinents représentant le couplage entre développement de la biomasse et fonctionnement du système, mais suffisamment simple pour une utilisation opérationnelle. Cette thèse s’est focalisée sur certains processus qui régissent le comportement macroscopique de tels systèmes. Nous avons étudié la modélisation de la réduction de la perméabilité induite par le développement du biofilm. Un modèle incorporant deux processus caractéristiques du colmatage (réduction de la taille pores et formation de « plugs ») a été développé. Ce modèle a été évalué pour une large gamme de données expérimentales. Une autre partie porte sur les processus d’adhésion initiale de la biomasse, processus important pour caractériser l’état initial du système. Sous l’hypothèse que les cellules bactériennes peuvent être traitées comme des colloïdes non rigides, une nouvelle corrélation a été développée pour estimer l’efficacité d’attachement des bactéries. Cette corrélation est basée sur l'analyse d'un large éventail de données expérimentales pour des conditions variées en termes d'électrolyte, débit et géométrie des milieux poreux, et introduit de nouveaux paramètres adimensionnels pour représenter les effets couplés des forces de Derjaguin-Landau-Verwey-Overbeek (DLVO), des forces hydrodynamiques et prendre en compte la géométrie des milieux poreux. Ces processus ont été introduits dans un modèle 1D développé pour la simulation numérique du transport de soluté en présence de biofilm dans un milieu poreux. Une autre question importante dans ce modèle était de représenter correctement le processus détachement de biofilm. Un autre trait distinctif de notre modèle est une tentative de rendre compte du processus de «sloughing» dans la modélisation du détachement de biofilm. Le « sloughing » est un processus différent de l'érosion, phénomène continu, et qui correspond à une élimination discrète d'une grande fraction de biofilm.Dans cette étude, le phénomène de « sloughing » a été incorporé séparément etodélisé comme un processus stochastique. Des simulations numériques ont été effectuées en utilisant OpenFoam pour implémenter le modèle. Des simulations avec et sans le terme de « sloughing » ont été effectuées et discutées dans le cadre des données de la littérature disponibles. / Solute transport coupled with biofilm growth in porous media is encountered in many engineered applications, for instance biofiltration of wastewater and air pollutant treatment. In terms of modelling, the interaction between biology, hydrodynamic and chemistry are still difficult to understand at the fine scale: that led to a wide dissemination of macroscopic model, simpler to handle. However, one issue consists in providing a macroscopic model complex enough to take into account the relevant processes accounting for the coupling between the biomass development and system functioning, but simple enough for operational use. This thesis focused on few selected processes that influence the macroscopic behavior of such system. First, we investigated the permeability reduction modeling accounting for biofilm development. A model including two features that result in permeability reduction (pore radius reduction and pore plugging) was developed. This model was assessed in a wide range of experimental data. Another part of the thesis focused on the initial biomass attachment that is an important feature to characterize the system initial state. Following the concept that bacterial cell can be treated as soft colloids, a new correlation equation was developed to estimate the bacteria attachment efficiency. This correlation is based on the regression analysis of a wide range of experimental data of colloid deposition in various electrolyte conditions, flowrates and geometries of porous media. New dimensionless parameters have been introduced to represent the coupled effects of Derjaguin-Landau-Verwey-Overbeek (DLVO) forces, hydrodynamic forces and to account for geometry of porous media. These features were introduced in a 1D dimensional model that have been developed for the numerical simulation of solute transport coupled with biofilm growth. An important issue in this model was to properly represent biofilm detachment. Another distinctive feature of our model is an attempt to account for the “sloughing” process in modeling biofilm detachment. Sloughing is a different process than erosion which corresponds to a discrete removal of large fraction of biofilm. In this study, biofilm sloughing has been separately accounted in the numerical modeling porous media bioclogging. Biofilm sloughing was considered as a stochastic process and quantified by random generator. So this discrete events could be incorporated into other continuous processes to determine the biomass transfer from biofilm to the liquid phase. Numerical simulations have been performed using OpenFoam to implement the model. Simulation with and without the sloughing term were performed and discussed in the frame of available literature data

Methicillin-resistant Staphylococcus aureus (MRSA) was originally recognized as a hospital acquired infection. However, it is now recognized that MRSA infections are frequently acquired in the community setting as well. As epidemiological studies and surveillance of MRSA continued over the past decade, agricultural sources of MRSA have also been recognized. Although direct person-to-person transmission of MRSA has been recognized as a major known route of transmission, a preliminary study has shown that aerosol exposures may also be an important mechanism of transmission, both occupationally to workers inside animal feeding operations and environmentally via exhaust ventilation to the outside e. In this study I aimed to 1) determine the concentration of viable MRSA inside and outside swine buildings known to be positive for MRSA, 2) determine the efficiency of the N95 respirator at protecting workers inside swine buildings, and 3) determine the efficiency of a biofilter unit at mitigating emissions of MRSA from a swine building. I hypothesize that remediation and control of airborne MRSA in animal feeding operations can be achieved by the appropriate use of N-95 respirators to protect workers and the addition of biofilters to the exhaust ventilation system to mitigate transmission of this emerging environmental contaminant to the outdoor environment. The results of the study indicate that MRSA in the respirable size range can be detected inside a swine building and 215 m downwind of the swine building. Aim 2 results indicated that the N95 respirator was efficient at protecting workers exposed to MRSA particles greater than 5 μm but not as effective with MRSA particles less than 5 μm. The results of aim 3 indicated that hardwood chips and western red cedar chips are efficient biofilter media for mitigating the emission of MRSA from a swine building. These studies showed that workers inside swine buildings and the outdoor environment can be protected against the transmission of MRSA with a respiratory program which includes the use of N95 respirators and biofilters as mitigation control measures.

No description available.