A importância do monitoramento de parâmetros físico-químicos e biológicos no meio ambiente torna-se cada vez mais evidenciada quando se busca o entendimento dos processos que ocorrem na natureza, sejam eles decorrentes de ações antrópicas ou naturais, ou ainda, como efetivo auxilio na gestão de ecossistemas aquáticos. Entre os parâmetros de interesse no monitoramento do meio aquático, o oxigênio dissolvido (OD) é, indubitavelmente, uma das variáveis fundamentais na caracterização de ecossistemas, pois este elemento está intimamente ligado à capacidade de respiração de peixes, plantas e de micro-organismos. Assim como o OD, o Potencial de Oxido- Redução (POR) assume papel importante no monitoramento de ambientes aquáticos, pois se relaciona com reações químicas óxido-redutoras e bioquímicas. Ainda, nesse contexto, a temperatura interfere significativamente nas taxas em que ocorrem as reações químicas e bioquímicas. Devido à importância desses parâmetros para o monitoramento ambiental, o presente trabalho teve como objetivo o desenvolvimento de microssensores eletroquímicos amperométricos para medição de oxigênio dissolvido (OD) tipo Clark, potenciométricos para medição de POR e de temperatura, bem como, sistemas eletrônicos compactos para leitura e software para visualização e armazenamento de dados de maneira autônoma, por meio de notebook ou PC. O sistema de aquisição conta com um módulo GPS para registro das coordenadas dos pontos de aquisição e módulo GPRS para transmissão de dados via celular. Foram desenvolvidos eletrodos com base na tecnologia de microssensores utilizados em estudos de biofilmes; recentemente introduzidos no Brasil e desenvolvidos no Departamento de Hidráulica e Saneamento da Escola de Engenharia de São Carlos da Universidade de São Paulo desde 2007, mediante apoio da Universidade de Montana EUA e FAPESP. O método proposto para sua fabricação visa produção com custos minimizados, podendo atingir 50% dos custos de sistemas convencionais para o mesmo propósito; isso decorre da miniaturização de componentes internos, pois assim como nos macro eletrodos, são empregados metais nobres como ouro, platina e prata. Os microssensores, sistemas eletrônicos e software foram validados através de testes de desempenho em laboratório. Em campo, foram avaliados por meio de medições realizadas no reservatório do Lobo (Itirapina - SP), para obtenção de dados limnológicos do reservatório, onde foram aquisicionados perfis de OD, POR e temperatura por meio de um traçado longitudinal com embarcação de pequeno porte e os pontos de medição foram vinculados às coordenadas GPS ao longo do trajeto do levantamento. Na foz dos principais afluentes do reservatório, foram coletadas amostras para análises complementares, buscando identificar alterações antrópicas e os níveis de trofia do reservatório para Fósforo Total e Profundidade (Secchi ZDS). Foi também observada a distribuição espaciais da comunidade fitoplanctônica. / The importance of the physicochemical and biological monitoring parameters in the environment becomes more and more evidenced when the understanding of the processes is looked at what happens in nature, whether they are from anthropic or natural actions. Among the parameters of interest in the aquatic mean monitoring, dissolved oxygen (DO) is undoubtedly, one of the fundamental items in the characterization of aquatic ecosystems, because this element is intimately linked to the breathing capacity of fish, plants and microorganisms of oxidizing substances present on that media. As well as DO, the ORP assumes an important role in aquatic monitoring, acting in the levels of oxide reduction and biochemical reactions that happen. Still, in that context, the temperature represents effective interference in the rates where chemical and biochemical reactions take place in the environment, even in the ones that concern DO and ORP. Due to the importance of these parameters for the environmental monitoring to better know the appropriate conditions and to plan solutions the present work seeks the development of amperometric electrochemistry micro electrodes for dissolved oxygen (DO) measurement Clark type, potentiometric for ORP measurement and temperature with the LM35component, as well as, compact electronic systems for reading and software for visualization and storage of data in an autonomous way, through notebook or PC. Yet, the data acquisition system foresees the application of a GPS module for data acquisition recordings of the coordinates points and a GPRS module for data transmission from cellular. The electrodes were developed based on the microsensors technology used in biofilms studies; recently introduced in Brazil and developed at the Hydraulics and Sanitation Department at School of Engineering of São Carlos at the São Paulo State University since 2007, through the support of the Montana State University USA and FAPESP. The proposed method for construction seeks production with minimized costs, it could reach 50% of the conventional systems costs for the same purpose, due to the internal components miniaturization, because as well as for macro electrodes, noble metals are used as gold, platinum and silver. The microsensors, electronic systems and software were validated through the tests carried out at the laboratory and through comparison with commercially found electrodes. In the field, they will be evaluated through acting tests in measurements carried out at the Lobo Reservoir (Itirapina SP Brazil), throughout the whole reservoir by using a small boat and the data acquisitions points were indexed to the GPS coordinate along the trajectory. Samples were collected at the main affuents of the reservoir for additional analysis, seeking identification of anthropic changes as well as the trophic level of the reservoir for Phosphorus and depth of the Secchi disk (ZDS). It was also observed the spatial distribution of phytoplankton community.

Questões de aeração forçada ou natural estão intimamente ligadas à capacidade de autodepuração dos corpos hídricos, ou seja, oxidar substâncias agressivas para resultar em baixo teor de toxicidade. Uma das etapas do processamento de efluentes consiste na dissolução de oxigênio em água e, para realizar essa dissolução, utilizam-se aeradores que são unidades (tanques) onde o ar é borbulhado no meio líquido, o qual se desloca em um regime contínuo de escoamento. Esta pesquisa refere-se à obtenção experimental de valores de viscosidade turbulenta para inserção em modelagem fenomenológica da transferência de oxigênio das bolhas de ar para o meio líquido. Tais modelos, se bem realísticos, podem contribuir aos estudos de gestão de recursos hídricos ou em operações nos tratamentos de efluentes líquidos. O método experimental empregado foi a velocimetria por imagem de partículas, no qual foi possível obter velocidades instantâneas do fluido (água). Estas consideram o movimento turbulento, que é o principal responsável pelo transporte de oxigênio da superfície para o seio do corpo hídrico, sendo que essa superfície pode ser livre para o ambiente, ou a superfície de uma bolha. Praticamente, o método consiste em correlacionar posições de partículas traçadoras em suspensão no fluido, as quais são assumidas ter a mesma velocidade do fluido. As posições consecutivas para fornecer a trajetória e a velocidade foram obtidas por imagens capturadas em uma freqüência definida através de uma câmera digital, onde a luz do laser contrastou as partículas em uma área desejada com uma precisão elevada. Então, nessa área (um plano), foi possível correlacionar um perfil de velocidades. Assim, os valores de viscosidade turbulenta foram obtidos para serem usados em modelagem da transferência de oxigênio, os quais poderão contribuir nos estudos de aeração em corpos hídricos. / Problems involving natural or forced aeration are intimately bind to the reaeration of water bodies. Pollutants are oxidized to yield low toxicity conditions. One of the steps of wastewater treatment consists in dissolving oxygen in water. To perform this, aeration tanks are used where bubbling air crosses the continuous liquid flow. This research focuses on the experimental determination of turbulent viscosity values to be used in modeling of oxygen transfer from air bubbles to the bulk liquid. Such models, if realistic enough, may contribute to water resources management studies or in wastewater treatment operations. Particle image velocimetry method was used, by means of which it became possible to obtain instantaneous velocities of the fluid (water). These velocities embody the turbulent flow, which is the main responsible for oxygen transport from the surface to the bulk liquid. This surface may be either facing the atmosphere or the interior of a bubble. In practice, the method consists in correlating tracking particles suspended in the liquid, which are supposed to have the same velocity of the fluid. The successive positions that give path and speed were obtained by images took in predefined intervals by a digital camera. The laser light illuminated the particles in a predefined area with high precision, making possible to determine velocity profiles. Turbulent viscosity values were so determined and may be used in the modeling of oxygen transfer, which may contribute to water body aeration studies.

The runoff of suspended solids and nutrients from land into the nation's lakes and rivers can have severe impacts on the health of these systems and their uses. High-frequency environmental data from sensors can provide insight into fundamental biogeochemical processes that dictate water quality and provide regulators with valuable knowledge on how to manage critical resources. The goal of this research was to utilize sensor technology, telemetry hardware, cyberinfrastructure, and water quality models to create a sensing system that will allow the investigation of the fate and transport of dissolved oxygen, suspended solids, nutrients, and other water quality parameters throughout a watershed dominated by agricultural activity. Deploying these sensors at multiple locations along the stream enabled the investigation of these processes from the fine scale to the larger watershed scale. Results from this research addressed both fundamental science and resource management issues regarding water quality. Using high-frequency data, a dramatic diel cycle in dissolved oxygen was observed with nonlinear dynamics which was successfully modeled mathematically, and excursions in water quality criteria were observed. In addition, a diel pattern in turbidity was discovered with higher levels at night likely caused by bioturbation (i.e. nocturnal activity of bottom feeding fishes) which resulted in higher suspended solids loadings during nighttime. Furthermore, the QUAL2K model was successfully calibrated for water quality using sensor measurements and grab samples from volunteer, IOWATER data. Nutrient loading rates (nitrate-N, orthophosphate, and total dissolved solids) were estimated along the entire creek and were similar to other Iowa streams. Volunteer environmental data were found to be helpful in model calibration for some parameters (e.g. TSS and nitrate). The construction and operation of a sensing system in Clear Creek contributed to water quality science and engineering. Findings from the configuration and field testing of sensing station components such as water quality sensors, power systems and communication hardware will aid the design of future sensing systems and environmental observatories. Integrating the methodology of this research with future observing systems will further our understanding of water quality processes and help maintain the health and value of our nation's water environment.

This pilot study was conducted to determine if an Electron Magnetics Oxygen and Hydrogen (EMOH) device can increase the dissolved oxygen (DO) concentration of a residential surface water. By using EMOH, DO concentration will increase and allow bacteria to remove the substrate that creates blue-green algae for which the City of Boynton Beach (City) receives complaints. Those complaints center on odors and the visual appearance of the ponds. The study was conducted in-situ at the INCA Pond system in the City of Boynton Beach, Florida with data collection taking place bi-weekly, using surface aeration techniques. Water sampling was conducted in the INCA Pond system via a handheld water sensor. Primary variable monitored included: water temperature, barometric pressure, DO concentration, and DO saturation (DOSAT). Biomass of dead algae at the bottom of the pond was also monitored to determine if increased DO concentration aided the biological digestion of the organic matter. Data analysis shows that exposure to EMOH treatment allowed the relationship between DO and temperature to change from a negative correlation (the expected relationship) to a positive trend. Furthermore, pressure and DOSAT became less correlated after exposure to EMOH effluent. In all, EMOH was shown to be an effective means of treating hypoxic pond water. The optimal EMOH effluent discharge is determined to be deep in the subject pond. Backed by research on the surface-air water and bubble-water oxygen transfer coefficients, DO concentration in the subject pond was 110% higher when effluent was directed down toward the floor of the pond. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Since its creation in the late 19th century, mass spectrometry has evolved into one of the most versatile analytical methods in science. To chart this evolution this thesis includes a historical overview of mass spectrometry and a description of the role of mass spectrometry in oceanography. The development and deployment of underwater mass spectrometers (UMS) at the University of South Florida's Center for Ocean Technology has made possible the collection of real-time data with greatly increased spatial and temporal density. The UMS was deployed via both remotely guided surface vehicles (GSV) and ship's cables to monitor a suite of dissolved gases and volatile organic compounds in saltwater and freshwater environments. Spectrometer data in Lake Maggiore, Florida were acquired at a rate of 0.7-3.6 seconds/sample for 2-3 hours. The resulting multi-analyte spectrometer data were recorded in real time with the Global Positioning System (GPS) observations of an associated surface vehicle and transmitted to a remote laptop computer via a wireless Ethernet link. These data were merged to create high-resolution maps of chemical distributions. Of particular interest were the co-varying oxygen and carbon dioxide mass spectrometer signals, diagnostic of photosynthesis-respiration processes, that were collected over a 10,800 square-meter area of the lake. The UMS was also deployed on a shipborne hydrowire in Saanich Inlet, a 200-meter deep fjord in the western Canadian province of British Columbia. The concentrations of a broad suite of dissolved gases were monitored on both downcast and upcast over a total depth range of 200 meters. Spectrometer data were acquired at a rate of 4.2 seconds/sample for the duration of the deployment. Mass spectrometer signals diagnostic of reduced species (CH4, H2S,) in the anoxic waters of the inlet below a depth of 100 meters were consistent with previous descriptions of the fjord's chemistry. The UMS was deployed on a remotely guided surface vehicle on the Hillsborough River in central Hillsborough County. Spectrometer data were acquired at a rate of 0.7 seconds/sample, and geographic location was recorded by an onboard GPS during a 2,640 meter transect of the river. Prior to the deployment, the mass spectrometer was calibrated using certified gas standards. The calibration experiments correlated mass spectrometer ion intensity data with dissolved gas concentrations, whereupon the mass spectrometer data collected during the deployment were reported in units of micromole/kilogram (µmol/kg). The mass spectrometer recorded changes in gas concentrations associated with changing physical conditions and biological activity along the 2,640 meters of the river that was transited by the GSV.

Water resource is one of the most important natural resources on earth. In recent years, due to the discharges of large industrial and domestic waste-water into the nature, water pollution problem is getting more and more serious and how to monitor the quality of water in real time has become a very important research issue. The dissolved oxygen is one of the critical indexes for evaluating the quality of water. Although the conventional dissolved oxygen detectors presented a high sensitivity and high accuracy, the high cost, large dimension, low capability of batch fabrication and real-time monitoring will limit their applications. In this thesis, an extended-gate field-effect transistor (EGFET) based dissolved oxygen microsensor is developed utilizing micro-electromechanical system (MEMS) technology. The gate voltages of EGFET under different concentrations of dissolved oxygen can be detected by the Cr/Au sensing electrode. To further enhance the sensitivity of the proposed microsensor, a polystyrene layer with very high permeation rate of the dissolved oxygen gas is adopted and coated on the surface of Cr/Au layer. The main processing steps of the presented microsensor involve four photolithographic and four thin-film deposition processes. The influence of the channel¡¦s width/length ratio, source/drain geometry and polystyrene additional layer on the sensitivity of the EGFET based dissolved oxygen microsensor are investigated in this study. The chip size of the implemented dissolved oxygen microsensor is 11 mm¡Ñ13 mm¡Ñ 0.5 mm and the sensing area is 1 mm¡Ñ1 mm. As the dissolved oxygen concentration varies from 2 ppm to 6 ppm, a very high sensitivity (35.36 mV/ppm) and sensing linearity (98.83%) of the proposed EGFET microsensor can be demonstrated. In addition, the response time of the presented dissolved oxygen microsensor is only about III 180~200 seconds, hence it is very suitable for developing a real-time monitoring microsystem.

Protection of potable water supplies demands a better understanding of the factors controlling migration of disease causing bacteria in subsurface environments. In this study, the migration behaviour of the waterborne pathogenic microorganisms Escherichia coli O157:H7 and Yersinia enterocolitica was investigated in water saturated granular systems. Both facultative bacteria were grown under aerobic and anaerobic conditions and further acclimatized to a microaerophilic or fully aerated environment for 21 h. Experiments were conducted using laboratory-scale packed columns over controlled extreme dissolved oxygen (DO) concentrations. The observed differences in the transport potential of these pathogens were found to depend strongly on the antecedent growth conditions under the tested environmental settings as well with the environmental DO in certain conditions. Further microbial characterization using cell titrations and FTIR spectroscopy gave a greater insight on the source of the surface charge that was found to dominate the attachment phenomena in sand packed columns. Techniques also revealed a probable role of other cell surface macromolecules (LPS) that could account for non-DLVO behaviour. The results illustrate the importance of considering physicochemical conditions relevant to the natural subsurface environment when designing laboratory transport experiments as evidenced by variations in microbe migration as a function of the DO under growth and acclimation. / Keywords: bacterial adhesion, bacterial transport, DLVO, physicochemical characterization, dissolved oxygen, porous media.

A fuzzy logic controller (FLC) for the dissolved oxygen (DO) concentration of a wastewater bioreactor is presented. The FLC is developed and tested based on simulations using first order plus dead time models obtained from experiments with an actual wastewater bioreactor. The FLC uses feedback of the error in DO concentration and rate of change of the DO concentration and manipulates the stem position of the flow control valves (FCVs) supplying air to the bioreactor. The proposed FLC is tested for robustness across several process models, two of which include proposed worst-case process conditions. The performance of the proposed hand tuned FLC is compared to that of a similarly tuned proportional-integral-derivative controller. The FLC is implemented as a lookup table for speed and ease of deployment. The disturbances present in the experimental step testing data are characterized and used as the basis for disturbing the control loop during controller performance testing. A low-pass filter is then included to subsequently smooth the feedback signal. The nonlinear relationship between the FCV stem position and output flow is modelled and included in the controller performance testing. A genetic algorithm (GA) is developed that manipulates the membership functions of the FLC to yield an optimal controller for the ensemble of process models. The ability of the GA to converge on an optimal FLC is verified through repeated trials. The performance of the GA optimized FLC is observed under realistic process conditions and is benchmarked against a manually optimized PID controller.

Intensity and types of land use have changed rapidly in the last century and in north-western Alberta this has coincided with the decline of Wapiti River watershed Arctic Grayling (<italic>Thymallus arcticus</italic>) populations. Data on diurnal dissolved oxygen (DO), chemical and physical stream habitat data were collected in nine sub-watersheds of the Wapiti River with historically abundant Arctic Grayling populations. Levels and fluctuations of DO and temperature were related to the status of populations; five of the nine streams had higher temperatures and lower DO during summer, anoxic conditions during winter and extirpated populations. Amount of disturbed land and road density within sub-watersheds were inversely related to DO levels and population status. Cumulative effects modelling suggests a possible mechanism for these relationships is increased phosphorous runoff, leading to impaired habitat. These relationships and thresholds may be used as a management tool to maintain or restore Arctic Grayling and other stream fishes.

No description available.