This thesis is an investigation on water reuse in the fresh-cut fruits and vegetable industry. Fresh water is used intensively in washing, cutting/peeling processes and disinfecting fruits and vegetables, as a result washwater with heavy solids is generated. Effective removal of solids is needed to allow for water reuse. Thus dissolved air flotation (DAF) and centrifuge with coagulation and flocculation process were explored for solid removal capabilities; some settling analysis was also conducted. Bench scale studies show DAF and centrifuge produce waters of similar quality (Turbidity). DAF is able to produce waters with higher UV transmittance and can work better with membrane filtration and UV disinfection. While centrifuge showed higher reduction in pathogen levels, it can be cost effective and compact in design. Membrane filtration feasibility showed that high quality waters (low turbidity) can be produced, but were unable to remove pathogens. Collimated beam results show UV disinfection can further be used to completely eliminate pathogens and allow for water reuse. This allows the processors to reduce their water foot-print, increase sustainability of their operations, and meet the increasing demand for fresh-cut fruits and vegetables.

The validation of UV reactors is currently accomplished by biodosimetry, in which the reactor is treated as a "black-box" and hence cannot account for the dependence of the dose delivery on the complex hydrodynamics and the spatial variation in UV intensity. Alternative methods, such as fluorescent microspheres as non-biological surrogates and computational fluid dynamics (CFD) simulations, have been developed; however, each method has its shortcomings. In this study, a novel technique for the spatial and temporal assessment of the hydrodynamics and the UV dose delivered and the link between these two factors in a lab-scale UV reactor using three dimensional laser induced fluorescence (3DLIF) is developed. This tool can also be utilized for the optimization of UV reactors and to provide data for validation of CFD-based simulation techniques. Regions of optimization include areas around the UV lamp where short-circuiting occurred, a longer inlet approach section that enhances the performance of the reactor by reducing short circuiting paths and a longer outlet region to provide greater mixing. 3DLIF allows real time characterization of mixing and dose delivery in a single lamp UV reactor placed perpendicular to flow by capturing fluorescence images emitted from a laser dye, Rhodamine 6G, using a high speed CCD camera. In addition to three-dimensional mixing, the technique successfully visualized the two-dimensional, transient mixing behaviors such as the recirculation zone and the von Karman vortices and the fluence delivery within the reactor, which has not been possible with traditional tracer test techniques. Finally, a decomposition technique was applied to the flow and fluence delivery based concentration data to reveal similar structures that affect these phenomena. Based on this analysis, changing the flow in the reactor, i.e. the Reynolds number, will directly affect the fluence delivery.

Bacteriophages are viruses that specifically infect bacteria. The bactericidal nature of lytic bacteriophages has been exploited by scientists for decades with the hope to utilise them in the fight against bacterial infections and antibiotic resistant bacteria in medical settings. More recently, the potential applications of bacteriophages for biocontrol in the agrifood and environmental sectors have been investigated in an attempt to develop ‘natural’ antimicrobial products. Bacteriophages have a couple of decisive advantages over conventional methods of controlling pathogenic bacteria, such as high host specificity, the ability to self-replicate, and the ability to evolve with their hosts. However, more research is needed to optimise the parameters for phage applications, including the impact of environmental conditions on lysis efficiency, multiplicity of infection, and to significantly minimise the emergence of bacterial resistance to phages. Temperature plays a key role in every biological activity in nature. It is also assumed that temperature has an effect on phage lysis efficiency. A comprehensive study of it and how it affects both the host cells and their corresponding phages is crucial to ensure the efficient removal of bacterial pathogens. In this thesis, temperature (as selected parameter) was investigated to determine its influence on the lysis effectiveness of the three different phages belonging to the family of the Myoviridea that were isolated and purified from a single water sample taken from a brook receiving treated wastewater. We used the multiplicity of infection of 1 in all of our study in this project. Temperature was found to have a significant impact on phage-mediated lysis efficiency. Both the temperature of incubation of the phage-bacteria mixture (incubation temperature) and the temperature history of bacterial hosts were found to have profound effects on plaque sizes as well as plaque numbers. Plaque size and number decreased with increasing temperature. For the phages examined, bacterial lysis was more efficient at 20°C compared to 30 or 37°C. Phages were suggested to be well adapted to the environment where they were isolated from with general implications for use in biological disinfection. Furthermore, the temperature history of the bacteria (prior to phage encounter) was found to have a modulating effect on their susceptibility to lysis. A second part of this study compared the performance of the three phages in regard to bacterial resistance. The emergence of bacterial resistance is a major obstacle to the success of bacteriophages applications. The use of multiple phages is typically recommended and has proven better than the use of a single phage. However, the bestway to perform phage treatment is still very unclear. This study therefore compared simultaneous addition of multiple phages (in form of a cocktail) with the sequential addition of the individual phages at different time points in trying to delay the emergence of bacterial resistance. The data obtained from this work suggest that lysis effectiveness can be adjusted to optimize any treatment goal. For fast initial bacterial clearance the use of a single phage with short time maximal lysis efficiency proved most efficient, while the simultaneous addition of phages in the form of a cocktail was most successful strategy in our study. Addition of selected phages sequentially can be normalized in such a way that is just as effective as a cocktail. A third part of this thesis looked into the susceptibility of bacteria that had undergone sublethal disinfection. We addressed the question whether bacteria subjected to sublethal doses of chlorine and UV are still susceptible to phage-mediated lysis. The chlorine treatments indicated the development of a phage-insensitive phenotype for a critical chlorine dose in the transition zone between live and dead. The remaining live (and culturable) bacteria were shown insensitive to the selected phage. The lowest UV exposure at 2.8 mJ/cm2 eliminated bacteria susceptibility to the phages. This phage- resistant phenotype may have serious consequences for the application of phages on foods or water that have previously undergone a weak disinfection regime.

La réutilisation des eaux usées traitées (REUT) constitue une ressource alternative pérenne et à fort potentiel notamment pour les régions soumises à un stress hydrique. L’objectif général de cette thèse est de définir les conditions nécessaires pour garantir la fiabilité d’une filière de traitement tertiaire pour la réutilisation. La première partie s’intéresse aux limites des méthodes de dénombrement des microorganismes indicateurs couramment employées, notamment en lien avec la contamination particulaire des effluents. Les résultats indiquent qu’il existe un risque de sous-estimation par ces méthodes pour de fortes charges en matières en suspension.La désinfection par rayonnement ultraviolet (UV) est souvent employée pour garantir la qualité sanitaire de l’eau distribuée. La deuxième partie de cette thèse vise à comprendre les mécanismes pouvant affecter l’efficacité des UV. Une corrélation linéaire a pu être mise en évidence entre la contamination particulaire des effluents à traiter et la baisse d’efficacité de la désinfection UV, caractérisée d’une part par la diminution de la constante d’inactivation des microorganismes exposés aux UV et d’autre part par le risque d’apparition d’un effet de traîne (fraction de microorganismes insensibles aux UV).La mise en place d’un prétraitement par filtration s’avère donc nécessaire en amont de la désinfection UV. La troisième partie de cette thèse a permis de définir les paramètres opératoires les plus adaptés à l’effluent. Enfin, le contrôle de la qualité sur l’ensemble de la filière est envisagé, avec notamment la démonstration de faisabilité d’un système de surveillance en continu basé sur la spectrométrie UV/Visible. / Wastewater reclamation is an ongoing and promising alternative resource in a context of water stress. In particular, this is a major issue in the Mediterranean region, and its effects tend to be intensified by global warming. The main objective of this PhD thesis is to define the conditions for ensuring the reliability of a tertiary treatment chain for wastewater reclamation. The first part deals with the limits of the methods used in routine for the enumeration of indicator microorganisms, in relation with particulate contamination. The results indicate that there is a risk of underestimation by these methods for high loads of suspended matter.Ultraviolet (UV) disinfection has been used for years to ensure the biological safety of reclaimed water. The second part of this work aims to understand the mechanisms which may affect the efficiency of UV disinfection. A linear relationship has been observed between the particulate contamination of the effluents to be treated and the disinfection efficiency loss, featured on one hand by the decrease of the inactivation constant of the microorganisms and on the other hand by the risk of tailing (UV-resistant fraction among the microorganisms).The implementation of a pre-filtration is thus necessary before UV disinfection. The third part of this work enabled to identify the filtration parameters suited for the effluents to be treated. Finally, quality control on the whole chain is considered, in particular with the demonstration of feasibility of a continuous control system based on UV/Visible spectrometry.

Landfilling is the most widely used method for the disposal of municipal solid wastes (MSW) in the United States due to its simplicity and low cost. According to the 2014 report on Advancing Sustainable Materials Management by the USEPA, only 34% of the total MSW generated in the US was recycled, while 13% was combusted for energy recovery. In 2014, 53% of the MSW generated, (i.e. 136 million tons) in the US was landfilled. The treatment of landfill leachates, generated by percolation of water through the landfill, primarily due to precipitation, has been found to be one of the major challenges associated with landfill operation and management. Currently, leachates from most landfills are discharged into wastewater treatment plants, where they get treated along with domestic sewage. Issues associated with treatment of landfill leachates due to their high nitrogen and heavy metal content have been widely studied. Recently, it has been observed that the organic carbon in landfill leachates, specifically humic and fulvic acids (together referred to as "humic substances") contain aromatic groups that can absorb large amounts of ultraviolet (UV) light, greatly reducing the UV transmissivity in wastewater plants using UV disinfection as the final treatment step. This interference with UV disinfection is observed even when landfill leachates constitute a very small fraction (of the order of 1%) of the total volumetric flow into wastewater treatment plants. Humic substances are present as dissolved organic matter (DOM) and typically show very low biodegradability. Removing these substances using chemical treatment or membrane processes is an expensive proposition. However, the concentrations of humic substances are found to be reduced in leachates from landfill cells that have aged for several years, suggesting that these substances may be degraded under the conditions of long-term landfilling. The primary objective of this research was to use a two-stage process employing thermophilic pretreatment followed by a mesophilic anaerobic membrane bioreactor (AnMBR) to mimic the conditions of long-term landfilling. The AnMBR was designed to keep biomass inside the reactor and accelerate degradation of biologically recalcitrant organic carbon such as humic substances. The treatment goal was to reduce UV absorbance in raw landfill leachates, potentially providing landfills with an innovative on-site biological treatment option prior to discharging leachates into wastewater treatment plants. The system was operated over 14 months, during which time over 50% of UV-quenching organic carbon and 45% of UV absorbance was consistently removed. To the best of our knowledge, these removal values are higher than any reported using biological treatment in the literature. Comparative studies were also performed to evaluate the performance of this system in treating young leachates versus aged leachates. Next-generation DNA sequencing and quantitative PCR (qPCR) were used to characterize the microbial community in raw landfill leachates and the bioreactors treating landfill leachate. Analysis of microbial community structure and function revealed the presence of known degraders of humic substances in raw as well as treated landfill leachates. The total number of organisms in the bioreactors were found to be higher than in raw leachate. Gene markers corresponding to pathogenic bacteria and a variety of antibiotic resistance genes (ARGs) were detected in raw landfill leachates and the also in the reactors treating leachate, which makes it necessary to compare these ARG levels with wastewater treatment in order to determine if leachates can act as sources of ARG addition into wastewater treatment plants. In addition, the high UV absorbance of leachates could hinder the removal of ARBs and ARGs by UV disinfection, allowing their release into surface water bodies and aiding their proliferation in natural and engineered systems. / Ph. D. / Municipal solid waste is most often disposed by dumping it in landfills. Percolation of water through these landfills due to precipitation or the intrusion of surface or groundwater, results in the formation of landfill leachate, a mixture of organic and inorganic contaminants, at the bottom of the landfill. Landfills are therefore lined with special materials to prevent leachate from seeping into soil or groundwater and have sophisticated collection systems to periodically extract and dispose leachate. Perhaps the most commonly used method for the disposal of landfill leachates is discharge into wastewater treatment plants, where leachates can cause toxicity to biological processes due to their high organic load as well as their substantial heavy metal content. In the last decade or so, it has been established that leachates can absorb UV light considerably by virtue of aromatic organic compounds present in them, causing inhibition of UV disinfection in wastewater treatment. Thus, leachates must be appropriately treated to reduce their capacity to absorb UV light prior to discharge into wastewater treatment plants. This study employed a novel two – stage reactor system to treat landfill leachates in order to reduce their UV-quenching ability. The system was successfully operated over 14 months and was able to remove more than half of the UV light absorbing organic carbon from landfill leachate. Additionally, samples of biomass isolated from untreated landfill leachates and the reactors treating them revealed the potential presence of pathogenic bacteria and antibiotic resistance genes. Preliminary data suggests that landfill leachates might have large antibiotic resistance content, higher than that observed in wastewater and other engineered systems.

Outbreaks of food-born illness associated with the consumption of unpasteurized juice and apple cider have resulted in a rule published by the U.S. Food and Drug Administration (FDA) in order to improve the safety of juice products. The rule (21 CFR120) requires manufacturers of juice products to develop a Hazard Analysis and Critical Control Point (HACCP) plan and to achieve a 5-log reduction in the number of the most resistant pathogens. Ultraviolet (UV) disinfection is one of the promising methods to reach this 5-log reduction of pathogens. The absorption coefficients of juices typically vary from 10 to 40 1/cm and can be even higher depending on brand and processing conditions. Thin film reactors consisting of two concentric cylinders are suitable for inactivating pathogens in juices. When the two concentric cylinders are fixed, the flow pattern in the gap can be laminar Poiseuille flow or turbulent flow depending on flow rates. If the inner cylinder is rotating, and the rotating speed of the inner cylinder exceeds a certain value, the flow pattern can be either laminar or turbulent Taylor-Couette flow. UV disinfection between concentric cylinders in laminar Poiseuille flow, turbulent flow and both laminar and turbulent Taylor-Couette flow was investigated experimentally and numerically. This is the first systematic study done on UV disinfection between concentric cylinders in all three flow patterns. The present work provides new experimental data for pathogen inactivation in each of the three flow patterns. In addition, the present study constitutes the first systematic numerical CFD predictions of expected inactivation levels. Proper operating parameters and optimum gap widths for different flow patterns are suggested. It is concluded that laminar Poiseuille flow provides inferior (small) inactivation levels while laminar Taylor-Couette flow provides superior (large) inactivation levels. The relative inactivation levels are: laminar Poiseuille flow < turbulent flow < laminar Taylor-Couette flow.