CAPES / Este trabalho apresenta os resultados da pesquisa sobre medidas da atividade de 226Ra em águas minerais engarrafadas compradas em estabelecimentos comerciais do Brasil. As medidas foram realizadas no Laboratório de Física Nuclear Aplicada da Universidade Tecnológica Federal do Paraná em cooperação com o Centro de Desenvolvimento e Tecnologia Nuclear (CDTN) da Comissão Nacional de Energia Nuclear (CNEN). O trabalho avalia a possibilidade do uso do equipamento RAD7 (Durridge Company) para medir a atividade de 226Ra em equilíbrio com 222Rn presente nas amostras de águas em nível compatível com 0,1Bq/L, o que significa uma precisão superior à prática usual do equipamento. Além disso, a pesquisa fornece o erro mínimo de medida da concentração de atividade do rádio possível de ser atingida com o uso do equipamento RAD7. A principal dificuldade encontrada na técnica desenvolvida foi diminuir os erros associados às medidas. Para desenvolver a metodologia otimizada foram realizados diversos testes que propiciaram a diminuição dos erros e asseguraram uma técnica inovadora para medidas de baixas concentrações de 226Ra em água, com o uso do detector eletrônico de radônio RAD7. O arranjo experimental foi baseado no detector eletrônico de radônio RAD7 e as medidas foram realizadas utilizando o kit RAD H2O que permite identificar a atividade de concentração do 222Rn em pequenas amostras de 40mL e 250mL. Os resultados mostraram que o erro mínimo ficou entre 0,02 a 0,07 Bq/L o que configura uma diminuição considerável e importante nos erros associados às amostras de baixas concentrações. Quando aplicada a metodologia otimizada e proposta, foi possível concluir que todas as amostras analisadas apresentaram valores abaixo que os estabelecidos pelas normas e recomendações e que os valores encontrados para as amostras possuem ordem de grandeza semelhante às encontradas na literatura. Desta forma, foi possível concluir que o detector eletrônico de radônio RAD7 pode ser utilizado nas medidas de 226Ra em águas para concentrações menores que 0,1 Bq/L, mas que para isto deve ser utilizada uma técnica como esta desenvolvida para otimizar o procedimento. / This thesis presents the survey results of measuring the activity of 226Ra in bottled mineral waters purchased in Brazilian market. The measurements were performed at the Laboratory of Applied Nuclear Physics at Federal Technological University of Paraná in cooperation with the Centre for Development and Nuclear Technology (CDTN) of the National Nuclear Energy Commission (CNEN). The study evaluates the possibility of using RAD7 equipament (Durridge Company) in order to measure 226Ra activity in equilibrium with 222Rn present in water samples at a level compatible with 0.1 Bq/L, which means greater accuracy than the usual practice of the equipment. Furthermore, the search provides the minimum error of radio activity concentration that can be achieved using the RAD7 equipament. The main difficulty of this work was to reduce the associated errors to the measure. To develop the optimized methodology were performed several tests that enabled the reduction of errors and ensure an innovative technique for measuring low concentrations of 226Ra in water, using the RAD7 radon electronic¬ detector. The experimental setup was based on the RAD7 and measurements were performed using the RAD H2O kit that identifies the activity concentration of 222Rn in small samples of 250mL. The results showed that the minimum error ranged from 0.02 to 0.07 Bq/L which constitutes a considerable and significant reduction in errors associated with low concentrations samples. When applied the optimized methodology proposed, it was concluded that all the samples had values below the established standards and recommendations and that the values found for the samples have similar order of magnitude to those found in the literature. Thus, the RAD7 radon detector electronics can be used in measurements of 226Ra in water at concentrations below 0,1 Bq/L, but for that, the technique developed in order optimize the procedure should be used.

A l’instar des villes des pays en voie de développement, la croissance de la ville de Bangui fut rapide. Le croît démographique en est la principale cause. La croissance urbaine s’est faite de manière irrégulière et illégale. La ville s’est développée dans une dualité entre les quartiers urbanisés, bien équipés et les quartiers non urbanisés, dépourvus des infrastructures urbaines de base. La politique urbaine de l’Etat, focalisée sur le schéma directeur d’aménagement et d’urbanisme (SDAU), n’est plus à la hauteur de répondre de façon optimale aux besoins de la ville. L’occupation anarchique de l’espace par des quartiers précaires, est la conséquence directe de la politique de l’Etat en matière de gouvernance urbaine. L’inapplicabilité des textes ou des lois qui caractérisent le régime foncier, ont conduit à la création des bidonvilles. Les services de l’eau et de l’assainissement sont en difficulté face à l’explosion urbaine de la ville. L’accès à l’eau potable et à l’assainissement de base de la population n’est pas totalement assuré par ces services. Il se pose alors, un sérieux problème de gouvernance de ces services face à la croissance urbaine de la ville. Le réseau de la société de distribution d’eau ne couvre pas l’ensemble de la ville, et le système d’assainissement est très détérioré. La société de distribution d’eau en Centrafrique (SODECA), n’assure que 32% de l’approvisionnement en eau de la population. Les quartiers défavorisés sont alimentés par des réseaux informels (bornes fontaines, les forages et les puits). Malgré une légère amélioration, l’approvisionnement en eau potable dans ces quartiers, reste un parcours du combattant. Les femmes et les enfants sont les plus touchés. L’espoir de partenariat public-privé (PPP) suscité en 1990, autour de l’eau par SAUR a donné un bilan mitigé en Centrafrique. / Following the example of the cities of the countries in the process of development, the growth of the town of Bangui was fast. Grows is the leading cause. The urban growth was done in an irregular and illegal was. The city developed in a duality between the districts urbanized equipped well and the not urbanized districts, deprived of the basic urban infrastructures. The urban policy of the State, focused on the town planning and master development plan (SDAU), is not any more worthy meeting in an optimal way the needs for the city. The anarchistic occupation of space by dangerous district is the direct consequence of the policy of the State as regards urban governance. The inapplicability of the texts or the laws which characterize the land mode, led to the creation of the slums. The services of water and the cleansing are in difficulty face the urban explosion of the city. The access to drinking water and basic cleansing of the population is not completely ensured by these services. It is posed then, a serious problem of governance of these services face the urban growth of the city. The network of the company of water supply in Central Africa (SODECA), ensured of only 32% of the water provision of the population. The disadvantaged districts are fed by abstract networks (terminals fountains, drilling and wells). In spite of a light improvement, the drinking water supply in these districts stays an assault course. The women and the children are touched. The hope of public-private partnership (PPP) caused 1990, around water by SAUR gave by assessment mitigated in Central Africa.

This research used the tracer study method to determine more accurate disinfectant contact times in the City of Carbondale Water Treatment Plant. In this investigation, three clarifiers were selected to be the experimental segments. Water samples coming from each clarifier and the confluence of the three clarifiers were analyzed to obtain the disinfectant contact times. Based on a continuous source of infinite duration model and the tool "Solver" in Microsoft Excel, this study optimized the experimental data. The experimental data and the optimized data were then analyzed to determine the disinfectant contact times using the graphical method and the numerical method. The disinfectant contact times obtained between using the experimental data and the optimized data, and between using the graphical method and the numerical method were then compared. The results from the numerical method on the optimized data were most accurate and reliable according to these comparisons. The results suggested that the disinfectant contact times were 192.7 min for the first clarifier when its flow rate was 5.72 ML/d; 161.46 min for the second clarifier when its flow rate was 5.99 ML/d; 156.06 min for the third clarifier when its flow rate was 6.26 ML/d; and 168.48 min for the confluence of all clarifiers when its flow rate was 17.5 ML/d, respectively. The feed flows increase down the distribution manifold changing the disinfectant contact times for the clarifiers.

In Sweden, the access to drinking water is something that often is taken for granted. But several incidents where regions have found themselves without drinking water shows that we should be more concerned about crisis management concerning drinking water. Regulations state that even in a situation with drinking water disturbance the municipality is responsible for providing all citizens with drinking water of acceptable quality. When drinking water is not delivered in regular pipelines it is called emergency water, which is an alternative way to distribute drinking water within the region. During a crisis it is important that the authorities can act quickly in order to minimize the consequences that will occur if a region is without drinking water. The National Food Agency (Livsmedelsverket) have therefore developed a guide for municipalities how to make an emergency water plan. It contains information of how to map and prioritize water users. This is a case study of Nordmaling Municipality that investigates how and why water users should be prioritized during a disturbance in drinking water. The aim has also been to locate emergency water containers for citizens and study the accessibility of these locations and the level of justice within the society connected to citizens (in)accessibility. In order to do this study, the guide from the National Food Agency have been studied along with consultation with the municipal administration. Then a quantitative Multi Criteria Analysis (MCA) in GIS has been performed in order to find “optimal” locations for emergency water resources. Recommendations from the National Food Agency have been followed within the frame, ability and visions of Nordmaling Municipality. The study displays the functions that will obtain emergency water, and recommendations and regulations behind the decisions. Along with 12 different locations which have been decided based on results from the MCA. Water users (with extra consideration to vulnerable water users) living outside of the geographical “catchment-area” of a location with emergency water have been studied. This has shown that the locations are not accessible for everyone within the municipality. Constrained accessibility can be seen especially for elderly and those living in the sparsely parts of Nordmaling, which displays an unjust society.

学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-09-25 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2850号 ; 請求記号: 新制/工/1419 ; 整理番号: 25535 / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13379号 / 工博第2850号 / 新制||工||1419(附属図書館) / 25535 / UT51-2007-Q780 / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 田中 宏明, 教授 藤井 滋穂, 教授 伊藤 禎彦 / 学位規則第4条第1項該当

A eutrofização acelerada dos mananciais superficiais, devido aos despejos de águas residuárias não tratadas, vem comprometendo a qualidade das águas utilizadas no abastecimento público. Como conseqüência desse processo, inúmeros registros de florações de cianobactérias são relatados em todo o mundo. Esses microrganismos são potenciais produtores de toxinas, as quais, presentes na água bruta que abastece uma Estação de Tratamento de Água (ETA), precisam ser removidas. As toxinas podem ter efeitos adversos à saúde, podendo causar danos hepatotóxicos, neurotóxicos e dermatotóxicos. A maioria das ETAs brasileiras tratam a água através do processo convencional de tratamento, compreendendo as etapas de coagulação, floculação, sedimentação, filtração e cloração. Esse tratamento é considerado eficiente para remover células de microrganismos, incluindo as cianobactérias. No entanto, suas toxinas não são afetadas, permanecendo na água tratada. Em função disso, alternativas de tratamento devem ser incorporadas ao tratamento convencional, visando remover a hepatotoxina microcistina a concentrações menores ou iguais a 1 μg.L-1, pois esse é o valor máximo permitido (VMP) pela Portaria nº 518/2004, do Ministério da Saúde, a qual define as diretrizes relativas ao controle e vigilância da qualidade da água para consumo humano. Nesse contexto, o objetivo do trabalho foi avaliar a eficiência do carvão ativado pulverizado (CAP), na remoção da cianotoxina microcistina presente na água utilizada para abastecimento público. Cinco amostras de CAP, produzidas a partir de madeira, osso, antracito e coco, foram caracterizadas e, para cada uma, determinadas as Isotermas de Freundlich. As Isotermas mostraram que os CAPs produzidos a partir da madeira apresentaram maior capacidade de remover microcistina. Os residuais de microcistina obtidos nestes ensaios foram ajustados ao modelo de decaimento logarítmico. Assim, para cada CAP, foi estabelecida uma equação geral do processo adsortivo, com a qual foi possível estabelecer dosagens de CAP, variando a concentração de microcistina inicial, para atingir uma concentração residual de 1 μg.L-1. A aplicabilidade da equação foi testada para uma amostra de CAP, em água natural, utilizando o coagulante policloreto de alumínio e concentrações iniciais de microcistina de 1, 10 e 100 μg.L-1. Os resultados mostraram que as dosagens de CAP calculadas foram suficientes para atingir o residual desejado. Além disso, através de ensaios de adsorção, em equipamento de jarros, foram simuladas as etapas de coagulação (utilizando coagulantes sulfato de alumínio e cloreto férrico), floculação, sedimentação e filtração do tratamento convencional para água natural acrescida de 100 μg.L-1 de microcistina. A aplicação do CAP foi realizada em dois pontos do tratamento (1) entrada da água bruta e (2) antes da aplicação do coagulante. A aplicação na entrada da água bruta possibilitou remoção da toxina abaixo do VMP, correspondendo à redução de, aproximadamente, 99% da concentração inicial de toxina. Já no ponto de aplicação antes do coagulante, não foi atingido o VMP. A partir dos estudos aqui realizados, concluiu-se que a melhor maneira de escolher o CAP para remoção de microcistina é a realização de ensaios específicos, como a Isoterma de Freundlich. Para uma remoção eficiente da toxina, o tratamento convencional mostra-se eficaz, desde que a etapa de adsorção seja incorporada ao tratamento. / The accelerated surface waters eutrophication, due to non treated residual waters discharges, has been harming the water quality utilized in the public supply. As a consequence of this process, countless records of cyanobacterias’ bloom are reported all over the world. These microorganisms potentially producers of toxins, which, when presented in the raw water that supplies the Water Treatment Plant (WTP), needs to be removed. The toxins can have harmfull effects to the health causing hepatotoxic, neurotoxic and dermatotoxic damage. Most of the Brazilian WTPs treat the water through the conventional water treatment process, covering the stages of coagulation, flocculation, sedimentation, filtering and chlorination. This treatment is considered efficient to remove microorganisms’ cells, including cyanobacterias. However its toxins are not affected, remaining in the treated water. Due to this fact, alternative treatment must be incorporated to the conventional one, trying to remove the microcystin hepatotoxin to concentrations lower or equal to 1 μg.L-1, the maximum allowed value (MAV) according to the Brazilian Ministry of Health Administrative Ruling 518/2004, which defines the rules related to the control and vigilance of the water quality for human consumption. In this context, the objective of the present work was to evaluate the efficiency of the powdered activated carbon’s (PAC), in the removal of the microcystin cyanotoxin present in the water for public supply. Five samples of PAC, made of wood, bone, antracite and coconut, were characterized and, for each one, were determined Freundlich adsorption isotherm . The isotherm showed that the PACs produced from wood presented the highest capacity of microcystin removal. The residuals of microcystin obtained in these tests were adjusted to the logarithmic decay model. Thus, for each PAC, it was established a general equation of the adsorptive process, in order to establish PAC dosages, varying the initial microcystin concentration, to achieve the residual concentration of 1 μg.L-1. The usage of this equation was tested for one sample of PAC, in natural water, using poly-aluminum chloride as a coagulant and the initial concentrations of microcystins of 1, 10 and 100 μg.L-1. The results showed that the dosage of PAC calculated was enough to achieve the desired residual. Besides this, through adsorptive tests, using jar’s equipments, were simulated the stages of coagulation (using alum sulphate and ferric chloride as coagulants), flocculation, sedimentation and filtering of the conventional treatment for natural water and with 100 μg.L-1 of microcystin added. The application of the PAC was performed in two points of the treatment: (1) entrance of the raw water and; (2) before the application of the coagulant. The application in the entrance of the raw water made possible the removal of the toxin under MAV, corresponding to a reduction of, approximately, 99% of the initial concentration of the toxin. Nevertheless, in the point of application before the coagulant, the MAV was not achieved. According to these studies, it was concluded that the best manner of choosing the PAC for microcystin removal is the realization of specific tests like a Freundlich isotherm. For an efficient removal of the toxin, the conventional treatment is efficient, once the adsorption stage is incorporated to the treatment.

A crescente contaminação dos sistemas de água doce com milhares de compostos químicos naturais e industriais é um dos principais problemas ambientais enfrentados pela humanidade. Embora a maioria destes compostos esteja presente em baixas concentrações, muitos deles podem causar efeitos danosos à saúde. Adicionalmente ao aumento da poluição, com a descarga de fertilizantes, pesticidas, fármacos, detergentes, derivados de petróleo, entre outros, grande parte das instalações para tratamento de água no Brasil opera com sistema convencional, não atuando de forma eficiente na remoção desses microcontaminates. Carvão ativado em pó (CAP) e granular (CAG) tem sido utilizados em muitos países para remoção de microcontaminantes e substâncias que causam gosto e odor na água. No Brasil já foram desenvolvidas diversas pesquisas com o emprego de CAP para remoção de gosto e odor e alguns contaminantes específicos de águas de abastecimento. Neste trabalho foi testado um CAG produzido a partir de cascas de coco para remoção por adsorção de microcontaminates orgânicos de águas de abastecimento. A água utilizada nos experimentos foi coletada no ponto de captação da Estação de Tratamento de Água (ETA) Lomba do Sabão. Para a caracterização da capacidade adsortiva do carvão foram realizados seis ensaios de isotermas de adsorção e quatro ensaios em colunas de leito fixo, projetada com base na norma ASTM D 3922. Os microcontaminantes orgânicos foram quantificados pela concentração de carbono orgânico dissolvido (COD), medido em analisador de carbono orgânico e por absorbância em espectofotômetro em comprimento de onda de 254nm. Os resultados indicam que o carvão utilizado tem baixa capacidade de adsorver a mistura de microcontaminantes presentes na água de abastecimento, quantificados como COD. Isto se deve, provavelmente, a falta de afinidade entre muitos destes compostos e o carvão. / Pollution growth in water bodies brought by daily discharge of thousands of chemicals from anthropogenic sources is one of the main environmental issues confronting humankind. Although most of these chemicals are present in very low concentrations, they can still be hazardous.to health. Additionally to the increasing levels of pollution brought by discharges of fertilizers, pesticides, prescription drugs and pharmaceuticals, detergents, and petroleum derivatives, among others, the standard processes that are used in drinking water treatment plants in Brazil are not effective to remove these micropollutants. Powdered (PAC) and granular (GAC) activated carbon have been used in many countries to remove micropollutants and taste and odor-causing substances from water. In Brazil, research has been made using PAC to remove taste and odor substances and specific micropollutants from water. In this research, GAC produced from coconut shells was used to test the removal of organic micropollutants present in source water by adsorption. Water used in this research was collected at the intake of Lomba do Sabão drinking water treatment plant in Porto Alegre. In order to assess the GAC adsorption capacity, six isotherm (batch) and four column (continuous flow) assays were performed according to ASTM D 3922 standard. Organic micropollutants were quantified by the concentration of dissolved organic carbon (DOC) and by ultraviolet absorption at 254 nm wavelength. The results suggest that the tested GAC have limited capability in adsorb the complex mixture of micropollutants that are present in source water, as measured by DOC. This is probably caused by lack of affinity between many micropollutants present in the mixture and the carbon.

It is common knowledge that water is one of the basic needs for human beings. However, the consumption of contaminated water can lead to waterborne diseases and fatalities. It is, therefore imperative to constantly monitor the quality of potable water. There are numerous technologies used for water quality monitoring. These technologies are relatively effective however these tests are expensive and complex to use, which then require experienced technicians to operate them. Other tests are not rapid, making consumers of water susceptible to waterborne diseases. In this study, dye-doped, surface functionalized silica nanoparticles (SiNPs) and surface-functionalized magnetic nanocomposites (MNCs) were proposed as materials that can be applied in order to reduce the time taken to get results as well as to make the processes less complex and portable. The aim of this study was to synthesize and characterize surface functionalized dye-doped SiNPs and surface functionalized MNCs for detection and preconcentration of in water. Additionally, proof of concept had to be shown using the synthesized materials. SiNPs were the materials of choice due to their easily functionalized surfaces and their strong optical properties. SiNPs are photostable and they do not leach in solution due to the inert nature of the silica matrix in aqueous media. MNCs were chosen as materials of choice for preconcentration of E. coli in water because they are easy to synthesize and they can be applied in various biological applications due to their functional groups. SiNPs were synthesized using the water-in-oil microemulsion. The SiNPs were further functionalized with amine and carboxyl groups and avidin. Thereafter, they were bioconjugated with biotinylated anti-E. coli antibodies. The pure and surface functionalized SiNPs were characterized using ATR-FTIR spectroscopy, FE-SEM, HR-TEM, Zeta Sizer, UV-vis spectroscopy and spectrofluorometry. The application of the dye—doped surface functionalized SiNPs in E. coli detection was characterized using the fluorescence plate reader. The SiNPs were spherical and uniform in size. They increased in size as they were being functionalized, ranging from 21.20 nm to 75.06 nm. The SiNPs were successfully functionalized with amine and carboxyl groups as well as with avidin and antibodies. Two methods were investigated for carboxyl group attachment (direct and indirect attachment) and the direct attachment method yielded the best results with a surface charge of -31.9 mV compared to -23.3 mV of the indirect method. The dye loading was found to be 1% after particle synthesis. The optical properties of the Ru(Bpy) dye were enhanced 3 fold when they were encapsulated in the Si matrix. The SiNPs were binding to the E. coli cells and enabled detection. MNCs were synthesized through in-situ polymerization. The MNCs were characterized using ATR-FTIR spectroscopy, SEM, TEM and XRD. The MNCs were successfully functionalized with carboxyl groups. The increase in size of the nanocomposites as seen in SEM images proved that the Fe3O4 was successfully encapsulated in the polymer matrix. The MNCs were proven to be magnetic by a simple magnetism test whereby they were separated in an aqueous solution using an external magnetic field. The antibody-labelled MNCs were binding to the E. coli cells as shown in TEM images. E. coli cells were removed from water at varying concentrations of 1x106 CFU/mL to 1x109 CFU/mL at 10 mL volumes. This study has demonstrated that dye-doped SiNPs amplify the signal of E. coli cells using fluorescence. The study has also demonstrated that the MNCs can be applied in sample preconcentration and enrichment for E. coli detection. However, further studies should investigate and optimize the combination of the two techniques in a point of use device for water quality testing of 100 mL-samples as per the requirement of the SANS 241 standard. / Civil and Chemical Engineering / M. Tech. (Chemical Engineering)

Novas tecnologias para o tratamento de água potável vêm sendo empregadas na medida em que a utilização de sais de alumínio tem apresentado correlação com doenças de envelhecimento mental nos seres humanos. Os coagulantes orgânicos de origem vegetal podem substituir de forma satisfatória estes sais no tratamento convencional de água potável. A utilização de processos combinados utilizando membranas de ultrafiltração com coagulação é uma alternativa aos métodos convencionais de potabilização. Com este cenário, o presente trabalho tem como objetivo comparar o desempenho operacional de uma planta piloto de ultrafiltração com membranas submersas para produção de água potável a partir do Lago Guaíba, utilizando o coagulante convencional poli (cloreto de alumínio) (PAC) e um coagulante orgânico oriundo da casca da Acácia Negra (Acacia maernsii) Tanfloc SG, com a análise da morfologia, massa molar de corte e permeabilidade hidráulica da membrana e com análises da água bruta e filtrada. As membranas de fibra oca de Poliéter Sulfona (PES) com massa molar de corte de 50 kDa, permearam sob pressão fixa de -500 mbar, com ação de borbulhamento em testes de 140 horas para avaliação da performance e testes de 10 horas para avaliação da qualidade de permeado. Os resultados indicaram semelhança no desempenho operacional dos dois coagulantes quanto à redução da permeância hidráulica relativa, e a qualidade do permeado indicou que mesmo com a ausência de flocos no tanque de alimentação, não houve passagem significativa de coagulante para o permeado. Os parâmetros de potabilidade indicaram o enquadramento da água produzida nos padrões organolépticos na atual Portaria 2914/2011 do Ministério da Saúde. / New technologies to water treatment have been applied as the aluminum salts commonly used have shown correlations with mental diseases in human beings. The organic coagulants from natural sources can satisfactorily replace those inorganic salts in drinking water treatment. The hybrid processes join ultrafiltration membranes with coagulation are alternatives to the standard potabilization. The present study compares the operational behavior of a submersed ultrafiltration (UF) pilot plant producing drinking water from Guaíba Lake, using poli (aluminum chloride) (PAC) and an organic coagulant extracted from Acacia maernsii Tanfloc SG. The membrane and the permeate were investigated. The polyether sulfone hollow fiber membranes filtered with a -500 mbar constant vacuum and air bubbles through 140 hours for performance test and for 10 hour for permeate quality verification. The results showed similarity of the relative hydraulic permeability of the two coagulants, and even with the absence of visible flocs in the membrane tank, there were no significant coagulant carryover through the membrane. The analytical data pointed that the water produced with both coagulants had concentration bellow the Brazilian organoleptic standards, according to the Portaria 2914/2011 of the Health Ministry.

O objetivo deste estudo foi comparar a concentração de flúor do biofilme dental de indivíduos residenteste em áreas com água fluoretada (AF) ou sal fluoretado (SF) e determinar o efeito do dentifrício fluoretado na concentração de flúor [F] do biofilme dental destes indivíduos. Dezesseis indivíduos resendentes em Montevidéu (SF) e dezesseis indivíduos residentes em Porto Alegre (AF) participaram deste estudo randomizado, cruzado e duplo-cego. Profilaxia dental e raspagem supragengivel foram realizaras antes de cada fase experimental. Durante as fases experimentais (14 dias/cada), os indivíduos escovaram os dentes, 2x/dia, com dentifrício fluoretado (DF) ou dentifrício não-fluoretado (DNF). As amostras de biofilme dental foram coletadas 8 horas após a última escovação. As análises de [F] no biofilme dental foram realizadas com um íon epecífico e as leituras foram convertidas em μgF¯/g de biofilme. Equações de estimativas generalizadas foram aplicadas para analisar a variância de medidas repetidas e as diferenças em cada desfecho. Uma maior [F] no biofilme foi observada na área com SF(2.69±0.10 IC 2.48–2.89) em comparação a área com AF (2.44±0.06 IC 2.32-2.57) quando do uso regular de DNF (p = 0.047). Entretanto, não houve diferença significativa na [F] no biofilme entre as áreas com SF (2.60±0.12 IC 2.37-2.83) e AF (2.81±0.10 CI 2.62-3.01) quando do uso de FD (p = 0.153). Adicionalmente, não foi observada diferença siginifcativa na [F] do biofilme quando DF e DNF foram usados nas áreas com SF (p = 0.294) e AF (p = 0.320). A maior [F] no biofilme observada na área com SF, sob uso regular DNF, pode não ter significância clínica, uma vez que ela desapareceu quando o DF foi usado. / The aim of this study was to compare the fluoride concentration in dental biofilm of subjects living in fluoridated- salt (FS) or water (FW) areas and to determine the effect of fluoride dentifrice on the fluoride concentration [F] in dental biofilm of these subjects. Sixteen individuals residing in Montevideo (FS) and sixteen individuals living in Porto Alegre (FW) participated in this randomized, double-blind, crossover study. Dental prophylaxis and scaling were performed prior to each experimental phase. During the experimental phases (14d/each) subjects brushed their teeth, 2x/day, with fluoridated dentifrice (FD) or non-fluoridated fluoride (NFD). Dental biofilm samples were collected 8 hours after the last toothbrushing. Analyses were performed with a fluoride ion-specific electrode and the reading was transformed into μgF¯/g biofilm. Generalized estimating equations were used to analyze the variance for repeated measures and the differences in each outcome. Higher biofilm [F] was found in FS (2.69±0.10 CI 2.48–2.89) compared to FW (2.44±0.06 CI 2.32-2.57) areas under regular use of NFD (p = 0.047). However, no significant differences were found on dental biofilm [F] between FW (2.60±0.12 CI 2.37-2.83) and FS (2.81±0.10 CI 2.62-3.01) areas under FD use (p = 0.153). Furthermore, no significant difference was observed in the biofilm [F] when FD or NFD were used in the FS (p = 0.294) and FW (p = 0.320) areas. The higher dental biofilm [F] was found in FS areas under NFD use may not have clinical significance once it disappeared when FD was used.