In 2015, the United nations presented the 17 Global Goals that would put an end to extreme poverty, inequality and climate change by 2030. One of these goals was clean water and sanitation. In 2015 1.8 billion people did not have access to clean water. Because of the contaminated water, one million people die every year worldwide. Africa, and especially Ghana, has had a high development in the recent years. The population has grown and more resources are needed. Clean water in Ghana is not a given matter, three million people live without access to clean water. To work towards the Global Goal water can be clean locally. A simple and cheap way is to build slow sand filters, which also are the purpose of this project. These filters purify the water mechanically, chemically and biologically. The biologically purification takes place in the biolayer that grows on the sand inside the filter and it consumes contaminants in the water. It takes about a month for the biolayer to be fully developed and clean the water to its full potential. The positive aspects with sand filters are that people get healthier and can save money that can be invested in education or business. It can also reduce the need for water in plastic bags or bottles and would reduce littering. The companies that produce this water could end their business and air pollutions would be reduced as well.   During this project, slow sand filters have been tested and evaluated in Sweden and Ghana with the purpose to develop a theoretical filter that benefits the biolayer under local conditions in Ghana, this was of the one aims. Experiments in Sweden showed that the flow decreased with increased sand height and decreased hydraulic head. In Ghana three filters were built with the sand heights 30, 50 and 80 cm to clean 7 litres of drinking water for a family of four. None of these produced drinkable water by WHO’s and EU’s standards.   The next aim was to understand which chemical and physical factors that effected the development of the biolayer. The detected relations were absolute conductivity, total alkalinity, coliform bacteria and oxidantial reduction potential which were between the biolayer in the 30 and 50 filters.   The flow rate in Ghana was too high and to lower it, a new diffuser with smaller holes would be built to get the recommended flow of 0,4 m3/m2/h. A too high flow broke the bound between the biolayer and made an uncomfortable environment. A sedimentation should be installed before the sand filter to reduce the variations of the incoming water such as turbidity, suspended solids etc., so the biolayer would flourish. It was not enough dissolved oxygen in the water so the pause period would be decreased to 12 hours to get more oxygen in the filter each day. For a sand filter to work as planned a lot of attention should be given to the filter. It is a system that should be used all the time for the best purification. To build a filter takes a lot of time and it also takes time for the biolayer to develop. If it is not going to be used much, another treatment method should be used.   The last aim was to evaluate the cost of the materials that could be bought locally to the filter. One filter cost about 130 GHS. / 2015 tog Förenta nationerna fram de 17 globala målen för att få ett slut på extrem fattigdom, ojämlikhet och klimatförändringen till år 2030. Ett av dessa mål handlar om rent vatten och sanitet. 2015 var det 1,8 miljarder människor som inte hade tillgång till rent vatten. På grund av det förorenade vattnet dör en miljon människor i hela världen varje år. Afrika, och speciellt Ghana, har haft en snabb utveckling de senaste åren. Folkmängden har ökat och mer naturresurser behövs. Rent vatten i Ghana är inte en självklarhet, tre miljoner människor lever idag utan tillgång till rent vatten i Ghana. Ett sätt för att jobba mot det globala målet är rening av vatten lokalt. Ett enkelt och billigt sätt är att bygga långsamsandfilter, vilket även var syftet med denna studien. Dessa filter renar vattnet mekaniskt, kemiskt och biologiskt. Den biologiska reningen sker av en biofilm som växer på sanden inuti filtret som konsumerar föroreningar i vattnet. Det tar ungefär en månad för biofilmen att bli färdigutvecklad och rena vattnet till sin fulla potential. Det positiva med sandfilter är att människorna skulle bli friskare och spara pengar som kan investeras på utbildning eller företag. Ur miljöpunkt skulle reduktionen av köpt vatten i plastpåsar och flaskor minska nedskräpningen och företagen som producerar dessa kan avsluta produktionen och därmed minska luftföroreningar.    Under detta projekt har långsamsandfilter utvärderats både i Sverige och Ghana för att utveckla ett nytt teoretiskt filter som gynnar tillväxten av biofilm under lokala förhållanden i Ghana, vilket var ett mål. Experimenten i Sverige visade att flödet sjönk med ökad sandhöjd, men även med minskat hydrauliskt tryck. I Ghana byggdes tre filter med sand höjderna 30, 50 och 80 cm för att rena 7 liter dricksvatten till en familj på fyra. Ingen av dessa lyckades producera drickbart vatten enligt WHO:s och EU:s standarder.   Nästa mål var att förstå vilka av de kemiska och fysiska faktorer som påverkade biofilmstillväxten. Det förhållanden som upptäcktes var absolut konduktivitet, total alkalinitet, coliform bacteria och oxidential reduction potential vilket fanns i 30 och 50 filtret.   Flödet i Ghana var för högt, så för att minska det skulle en diffusör med mindre hål byggas för att få det rekommenderade flödet 0,4 m3/m2/h. Ett för högt flöde gjorde sönder bindingen mellan biofilmen och skapade en otrivsam miljö. En sedimentation skulle installeras innan sandfiltret för att minska variationer på ingående vatten i filtret för att få biofilmen att trivas bättre. Det fanns för lite löst syre i vattnet och om pausperioden minskas till 12 timmar skulle mer syre i filtret varje dag. För att ett sandfilter ska fungera som planerat måste mycket tid läggas på filtret. Sandfilter är ett system som bör används ofta för bästa rening. Att bygga ett filter kräver mycket tid, samt att det tar tid innan biofilmen har utvecklats. Om sandfiltret inte kommer används mycket föreslås att en annan metod används istället.   Det sista målet var att utvärdera kostnaden av materialen som kunde köpas lokalt till filtret. Ett filter kostade runt 130 GHS.

Magister Scientiae Dentium - MSc(Dent) / Aim: To determine whether there was any significant difference in the antimicrobial activity of 4 herbal toothpastes against cultures of 3 primary plaque colonizers (Streptococcus mutans, Streptococcus sanguinis and a non-specific alpha;-heamolytic streptococcus). / South Africa

Les travaux présentés traitent des cinétiques de décrochement des biofilms bactériens formés au sein des équipements communément utilisé dans les agro-industries. Deux espèces bactériennes Pseudomonas et Bacillus ayant une forte capacité à former des biofilms dont la présence quasi permanente est reportés dans les industries alimentaires (viande, lait, légumes frais…) ont servi de modèles pertinent pour ces travaux. Par ailleurs Bacillus, bactéries potentiellement pathogènes capable de former des spores dont les capacités à adhérer et résister aux environnements chimiques et thermiques défavorables (détergents, traitement de pasteurisation, stérilisation) sont reconnues pour présenter un risque sanitaire majeur pour l’agro-industrie du fait de la contamination des produits alimentaires par l’outil de fabrication lui-même. Deux type d’études ont été effectués sur le nettoyage d’équipements utilisés en industrie agroalimentaire.Une première approche cinétique a été mise en œuvre pour étudier l’élimination de ces biofilms des surfaces au cours du nettoyage. Nous avons cherchés à identifier les rôles respectifs de l’action mécanique via la contrainte pariétale générée par l’écoulement ou chimique via différentes concentrations en NaOH puis la combinaison des deux actions chimiques et mécaniques. Un modèle biphasique a été proposé pour décrire ces cinétiques de nettoyage en pertinence avec deux phases très distinctes que nous interprétons comme l’élimination de deux fractions différentes du biofilm. Un détachement plus ou moins rapide (1 à 5 min) correspondrait à l’élimination de structure tridimensionnelles composées ou non d’exopolymères suivi par un détachement lent des cellules directement en contact avec les surfaces.Dans le cas des biofilms à Bacillus, il existe une fraction du biofilm composée par des spores pouvant représenter près de 90% du biofilm. Cette fraction particulière semble s’éliminer plus rapidement dans la première phase et pas du dans la seconde phase. Les données préliminaires sur biofilms mixtes montrent une résistance accrue de l’ensemble qui se traduit par une plus grande résistance de la partie de biofilm constituée par des cellules à Pseudomonas.La seconde thématique développée traite de la possible récontamination par les sopres de Bacillus décrochées lors du processus de nettoyage.La réadhésion des bactéries à pu être prouvée par le positionnement des tubes dans le circuit de nettoyage, ainsi que par l’utilisation d’un matériel complexe (vanne bidirectionnelle) communément utilisé dans les agro-industries. Ces travaux ont permis d’identifier les conditions présidant à cette récontamination. La conception hygiénique des outils de transformation prend tout son sens ici. / This work deals with removal kinetics of bacterial biofilms potentially formed in commonly used equipment in agro-industries. Two bacterial species Pseudomonas and Bacillus with a strong ability to form biofilms in which the almost permanent presence is reported in the food industry (meat, milk, vegetables…) were chosen as relevant models for the study. Moreover Bacillus, potentially pathogenic bacteria can form spores which are known to strongly adhere to solid surfaces and for their ability to withstand adverse environments as thermal and chemical detrimental conditions (detergents, pasteurization or sterilization temperatures). Bacillus species are known to pose a major health risk for agro-industry is contamination of food by the technical equipment itself.Two main areas were considered in the field of food processing equipment cleaning.At first a kinetic approach was implemented to study the removal of biofilms from surfaces during cleaning operations. Thus respective roles of the mechanical action (wall shear stress under turbulent flow regime), the chemical action (different NaOH concentrations) and the combination of both chemical and mechanical actions were studied. A biphasique model was proposed to describe cleaning kinetics according to the observation of two very different phases which we interpreted as the elimination of two different fractions of the biofilm. A more or less fast detachment in 1 to 5 min would correspond to the three-dimensional elimination of structure with more or less exopolymeric materials followed by a slow detachment of bacteria cells directly in contact with solid surfaces. In the case of Bacillus, can represent about 90% of the total biofilm. Spores removal appeared to be a two phases phenomenon as the whole biofilm. However, the removal was essentially observed during the short first phase of the kinetics. Preliminary data on mixed biofilms with both species Bacillus and Pseudomonas had shown an increase in their resistance to cleaning comparing to the corresponded monospecies biofilm counterpart. This is really significant for Pseudomonas. The second developed theme considered as a consequence of the above one deals with possible equipment re-contamination by Bacillus spores removed during cleaning operations. Post contamination of food processing equipment during cleaning was thus observed In pipes located at different places in the cleaning loop, as well as in more complex materials as a mixproof valve commonly encountered in Dairies. This work allowed us to identify all the conditions explaining such phenomenon. Equipment hygienic design issues appeared to be here.

Clostridium difficile infection (CDI) is a major healthcare-associated disease with high recurrence rates. Host colonization is critical for the infectious process, both in first episodes and in recurrent disease, with biofilm formation playing a key role. The ability of C. difficile to form a biofilm on abiotic surfaces is established, but has not yet been confirmed in the intestinal tract. Here, four different isolates of C. difficile, which are in vitro biofilm producers, were studied for their ability to colonize germ-free mice. The level of colonization achieved was similar for all isolates in the different parts of the murine gastrointestinal tract, but pathogen burden was higher in the cecum and colon. Confocal laser scanning microscopy revealed that C. difficile bacteria were distributed heterogeneously over the intestinal tissue, without contact with epithelial cells. The R20291 strain, which belongs to the Ribotype 027 lineage, displayed a unique behavior compared to the other strains by forming numerous aggregates. By immunochemistry analyses, we showed that bacteria were localized inside and outside the mucus layer, irrespective of the strains tested. Most bacteria were entrapped in 3-D structures overlaying the mucus layer. For the R20291 strain, the cell-wall associated polysaccharide PS-II was detected in large amounts in the 3-D structure. As this component has been detected in the extrapolymeric matrix of in vitro C. difficile biofilms, our data suggest strongly that at least the R20291 strain is organized in the mono-associated mouse model in glycan-rich biofilm architecture, which sustainably maintains bacteria outside the mucus layer.

La maladie de Crohn (MC) est une affection inflammatoire chronique du tube digestif dont l'étiologie est multifactorielle. Les lésions iléales des patients atteints de MC sont anormalement colonisées par des souches pathogènes de Escherichia coli appartenant au pathovar AIEC («Adherent-Invasive E. coli»). Ces souches sont capables d'adhérer et d'envahir les cellules épithéliales intestinales, et ont la capacité de survivre et de se multiplier fortement en macrophages en induisant une synthèse intense de TNF-α. L'objectif de ce travail s'inscrit dans la compréhension des mécanismes permettant aux bactéries AIEC de coloniser la muqueuse intestinale et d'induire les stades précoces de la pathologie. Une précédente étude menée au laboratoire avait permis de mettre en évidence l'importance de l'activation de la voie de régulation dépendante du facteur bactérien sigma alternatif RpoE (ou σE) dans le processus d'adhésion et d'invasion des cellules épithéliales intestinales par la souche AIEC de référence LF82 via l'expression des pili de type 1 et des flagelles. En continuité de ces travaux, nous montrons que l'activation de la voie de signalisation dépendante du facteur σE est également primordiale pour la capacité des souches AIEC à former des biofilms, et une analyse bioinformatique ayant pour but d'identifier les gènes régulés par σE a montré que l’opéron waaWVL, impliqué dans la biosynthèse du lipopolysaccharide, est primordial pour la formation de biofilm par les souches AIEC. De plus, nous avons mis en évidence que les long polar fimbriae (LPF) sont impliqués dans le ciblage de l'épithélium associé aux plaques de Peyer par les bactéries AIEC, et ceci en leur permettant de cibler spécifiquement les cellules M. L'inactivation du gène Nod2, gène de susceptibilité à la MC, conduit à une augmentation du nombre de plaques de Peyer ainsi que des cellules M à leur surface, indiquant que les bactéries AIEC pourraient tirer avantage d'une susceptibilité génétique pour cibler les plaques de Peyer. / 2026/5000Crohn's disease (CD) is a chronic inflammatory condition of the gastrointestinal tract with a multifactorial etiology. The ileal lesions of MC patients are abnormally colonized by pathogenic strains of Escherichia coli belonging to the AIEC ("Adherent-invasive E. coli") pathovar. These strains are able to adhere and invade intestinal epithelial cells, and have the ability to survive and multiply strongly in macrophages by inducing intense TNF-α synthesis. The aim of this work is to understand the mechanisms by which AIEC bacteria colonize the intestinal mucosa and induce early stages of the pathology. A previous study carried out in the laboratory had made it possible to highlight the importance of the activation of the regulatory pathway dependent on the bacterial factor sigma alternative RpoE (or σE) in the process of adhesion and invasion of intestinal epithelial cells by the AIEC reference strain LF82 via expression of type 1 pili and flagella. As a continuation of this work, we show that the activation of the σE-dependent signaling pathway is also essential for the ability of AIEC strains to form biofilms, and a bioinformatic analysis aimed at identifying σE-regulated genes. showed that the waaWVL operon, which is involved in the biosynthesis of lipopolysaccharide, is essential for biofilm formation by AIEC strains. In addition, we have shown that long polar fimbriae (LPF) are involved in the targeting of Peyer's plaque-associated epithelium by AIEC bacteria, allowing them to specifically target M cells. Inactivation of the MC susceptibility gene, Nod2, leads to an increase in the number of Peyer's patches as well as M cells on their surface, indicating that AIEC bacteria could benefit from genetic susceptibility to target Peyer's patches.

This thesis examined the antimicrobial activity of select neotropical plants from Costa Rica and traditional Q’eqchi Maya medicines from Belize. In particular the potential for interference with bacterial quorum sensing (QS) and biofilm formation as well as fungal growth were assessed. Of one hundred and twenty six extracts collected from Costa Rica, one third showed significant QS inhibition while 13 species displayed more biofilm inhibitory activities than the positive control allicin. The active species belonged to the Lepidobotryaceae, Melastomataceae, Meliaceae, Sapindaceae, and Simaroubaceae. Twelve Marcgraviaceae species were tested for the same biological activities; of these, three showed similar QS inhibition to that of the positive control Delisea pulchra (Greville) Montagne and five with at least 30% biofilm inhibition. Only one species inhibited fungal growth – Marcgravia nervosa Triana & Planch. Bioassay-guided isolation of this plant resulted in the identification of the active principle as a naphthoquinone, with a minimum inhibitory concentration (MIC) ranging from 85 to 100 μM against Saccharomyces cerevisiae. Similarly, sixty one Q’eqchi’ Maya medicinal plant species were evaluated for their antimicrobial activities. Of these, four species showed more QS inhibition than D. pulchra, seven with comparable biofilm inhibitory activities that of allicin, and two with similarly antifungal activity to berberine. Two spirostanol saponins were isolated from Cestrum schlechtendahlii G.Don, an active antifungal plant. The major saponin showed growth inhibition against Saccharomyces cerevisiae and Fusarium graminearum, with MICs of 16.5 μM and 132 μM, respectively. Further analyses of this compound using chemical genomics suggested that its antifungal mechanism of action is pleiotropic, affecting multiple targets. Taken together, these findings showed that neotropical plants and traditional Q’eqchi’ Maya medicines contain phytochemicals that interfere with bacterial biofilm formation and quorum sensing as well as fungal growth.

Les sols qui ne rencontrent pas les normes d’ingénierie civile doivent êtres soumis à des améliorations géotechniques car les vibrations causées par les tremblements de terre ou par la surcharge sur des infrastructures en hauteur peuvent mener à la liquéfaction partielle ou totale des sols saturés en eau. Ceci peut donc entrainer des dommages importants aux structures construites sur ces sols. Certaines méthodes existent pour remédier à ce problème, mais elles demeurent couteuses et parfois toxiques car elles utilisent de l’acrylamide et des lignosulfates. La bio-précipitation in situ de calcite dans les sols représente une méthode alternative. Le tout se fait avec des bactéries qui démontrent une activité uréolytique. La présente étude s’est intéressée à l’activité uréolytique des souches Escherichia coli, Sporosarcina ureae, Bacillus pasteurii, Lysinibacillus sphaericus, Bacillus subtilis et Bacillus megaterium. Les résultats démontrent que l’urée est seulement dégradée par les souches S. ureae et S. pasteurii. L’incubation de S. ureae en présence de Ni2+ (0.1-1 ppm) et Fe2+ (1-10 ppm) a toutefois permis d’augmenter l’activité catalytique de la souche, ce qui démontre l’importance des éléments nutritifs lors de l’hydrolyse de l’urée. Afin de tester l’activité uréolytique des autres souches, nous avons introduit un système d’expression uréase dans la souche E. coli en substituant des amino-acides dans la structure primaire des protéines. Suite à cette modification, l’activité uréolytique de E. coli s’est améliorée et est devenue comparable à celle des souches S. ureae et S. pasteurii. L’injection de S. ureae et du mutant E. coli dans des sables non-consolidés a permis de cimenter de façon significative (p < 0.05) le matériel par rapport à des sables non inoculés, et ce après seulement 48 heures. Le transfert du système recombinant de E coli vers S. ureae est présentement en cours. Ces résultats prometteurs indiquent qu’il est possible de stimuler la précipitation in situ de calcite en utilisant des bactéries et de stabiliser les sols prônes à la liquéfaction. === Soils often do not satisfy functional requirements for civil engineering projects and as a result geotechnical improvements to soils are often made. Dynamic shaking during earthquakes or static overloading by overlying structures may still result in liquefaction in partially or fully water saturated soils. These have little bearing capacity for structures. Severe damages can result. Moreover, preventative soil grouting strategies are expensive, toxic, and permanent due to acrylamides, lignosulfonates, and otherwise harmful compounds present therein. Alternative methods of strength enhancement are advisable. Microbial induced calcite precipitation (MICP) was assessed in this investigation to consolidate loose, sandy soils. Ureolytic activty of Escherichia coli, Sporosarcina ureae, Bacillus pasteurii, Lysinibacillus sphaericus, Bacillus subtilis and Bacillus megaterium were assessed. Urea was readily degraded foremost by S. ureae and next by S. pasteurii with no significant (p <0.05) activity in other strains. Incubation of S. ureae with 0.1 - 1ppm Ni2+ and 1-10ppm Fe2+ was shown to improve catalytic activity, suggesting their importance as a dietary source for urea hydrolysis. A urease expression system was established in E. coli and particular amino acid substitutions in protein primary structure made. Enhanced ureolytic activity was observed in these E. coli mutants, comparable to native S. ureae activity. Application of wild type S. ureae and recombinant E. coli for MICP in a model sand showed significant (p < 0.05) improvements compared to controls after 48 hours. Transfer of the recombinant system in E. coli to S. ureae is currently underway. These results provide valuable insight affirming that a practical system for the application of MICP may be feasible in the field for the strength enhancement of native and construction-laid loose, sandy soils.

Please read the abstract in the section front of this document. / Dissertation (MEng)--University of Pretoria, 2012. / Chemical Engineering / unrestricted

Legionella pneumophila est une bactérie intracellulaire facultative retrouvée aussi bien dans les environnements aqueux naturels qu'artificiels. Cette bactérie est l'agent de la légionellose, une pneumopathie sévère. Les milieux aqueux sont colonisés par des biofilms, une association de micro-organismes enveloppés d'une matrice exopolymérique. Les légionelles sont capables de coloniser et de survivre au sein de ces biofilms. Dans les réseaux d'eaux, les biofilms sont la cible de la prédation des amibes qui se retrouvent ensuite parasités par les légionelles et favorisent ainsi leur multiplication. Nous avons étudié l'impact de l'origine de la multiplication des légionelles sur la colonisation et la formation de biofilms. Notre étude a démontré que dans tous les cas les légionelles sont présentes à la surface de biofilms préformés. Notre étude a mis en évidence que les légionelles issues de la multiplication au sein d'amibes sont capables de former des agrégats compacts empaquetés dans une matrice exopolysaccharidique. Ce phénotype « biofilm » se manifeste après induction par une molécule amibienne en cours de caractérisation. De plus, notre étude a mis en évidence l'existence d'un nouveau système de communication de type Quorum Sensing permettant une communication inter et intra-espèce qui permet l'induction de ce phénotype chez les légionelles. / Legionella pneumophila is a facultative intracellular Gram-negative bacterium colonizing freshwater as well as artificial environments. This bacterium is the agent of Legionnaires' disease, a severe pneumonia. Water network are colonized by biofilms, an association of microorganisms embedded in exopolymeric matrix. Legionella are able to colonize and survive within biofilms which are the major source of human infection. In water systems, biofilms are the target of amoeba predation that can be parasitized by Legionella. Amoebae are the major multiplication site of Legionella in the environment.We studied the impact of multiplication origin on colonization and biofilm formation by Legionella. Our study demonstrated that Legionella whatever their origins are present at the surface of pre-formed biofilms. Our study showed that Legionella issued from multiplication within amoebae are able to form compact aggregates packed in an exopolysaccharidic matrix. This "biofilm" phenotype occurs after induction by an amoebic molecule that has to be characterized. In addition, our study revealed the existence of a new QS system for inter and intra-species communication that allows the induction of this biofilm phenotype to other Legionella.

Orientadores: José Euclides Stipp Paterniani, Túlio Assunção Pires Ribeiro / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-29T00:00:03Z (GMT). No. of bitstreams: 1 Santos_FlaviaFerreiradeSouzados_D.pdf: 6754875 bytes, checksum: 9a804a4e184846e60d2063d6b1aa1326 (MD5) Previous issue date: 2015 / Resumo: O nãotecido sintético é um material de fácil obtenção e baixo custo, cujo uso na filtração lenta juntamente com areia acarretou em resultados satisfatórios, em termos de qualidade de água produzida e facilidade de operação. Esta pesquisa teve como objetivo avaliar o desempenho de um filtro lento com meio filtrante constituído exclusivamente por nãotecido sintético em diferentes espessuras e compará-lo ao desempenho de um filtro lento de areia tradicional. Construiu-se um sistema piloto de filtração em que os dois filtros lentos operavam em paralelo sob influência de três taxas de filtração (3, 6 e 9 m3.m-2.dia-1). No decorrer das carreiras de filtração foram monitorados a evolução da perda de carga de cada filtro, os parâmetros físico-químicos e bacteriológicos da água bruta e água tratada pelo filtro de areia e por cada uma das 12 espessuras (entre 1 e 40 cm) do filtro de nãotecido. O filtro lento de nãotecido proporcionou carreiras de longa duração, quando comparado ao filtro de areia, além de reduzir a frequência e a complexidade do processo de limpeza do filtro. A formação da schmutzdecke foi observada na camada superficial do filtro de nãotecido, o qual teve período de amadurecimento semelhante ao filtro de areia, aproximadamente 15 dias. O desempenho satisfatório do filtro lento de nãotecido abrangeu as três taxas de filtração avaliadas. Em termos de remoção de cor aparente e turbidez da água bruta, atendeu os padrões de potabilidade de água designados pela legislação vigente. E, em termos de remoção de bactérias heterotróficas, coliformes totais e E. coli, o filtro de nãotecido alcançou eficiência superior a 99,5%, estatisticamente similar ao filtro lento de areia. Os resultados obtidos indicam que a espessura ótima de nãotecido sintético para remoção de cor aparente e turbidez da água seria de 25 cm, e sugerem que a espessura de 15 cm de nãotecido seria suficiente para remoção de bactérias, com possibilidade de emprego de taxa de filtração considerada elevada para o tratamento por filtração lenta (9 m3.m-2.dia-1). Desta forma, concluiu-se que o meio filtrante constituído exclusivamente por nãotecido sintético de 25 cm de espessura tem potencial para substituir a areia no tratamento de água por filtração lenta, uma vez que obteve desempenho similar ao filtro lento de areia, além de simplificar os procedimentos operacionais e de manutenção do filtro / Abstract: Non-woven synthetic fabric is an easily available and low-cost material which has brought satisfactory results in terms of both the quality of produced water and its operational value. The aim of this research is to assess the performance of a slow filter made up exclusively of non-woven synthetic fabrics of a number of different thicknesses and to compare it to that of a traditional sand filter. A pilot filtering system was built where the two slow filters operate in a parallel way under the influence of three filtering rates (3, 6 and 9 m3.m-2.d-1). Along the filtering runs the evolution of the headloss and the physical-chemical and bacteriological parameters of both raw water and water treated through the 12 thicknesses (ranging from 1 to 40 cm) of non-woven were monitored as well as that filtered through sand. The slow non-woven filter yielded long-term runs when compared to the sand filter, as well as reducing the frequency and complexity of the filter¿s cleaning process. The formation of schmutzdecke was observed on the superficial layer of non-woven filter, a process which had a similar maturing period to that of the sand filter, approximately 15 days. The satisfactory performance of the slow non-woven synthetic fabric filter covered all three filtering rates. In terms of the removal of apparent color and turbidity of raw water it met the drinkability standards set by the existing legislation. In terms of the removal of heterotrophic bacteria, total coliform and E. coli the non-woven filter obtained an efficiency level above 99,5%, statistically similar to the slow sand filter. The results indicate the optimal thickness of non-woven synthetic fabric for apparent colour and turbidity removal to be 25 cm, and suggest that a 15cm thickness would be enough to remove, with the possibility of using filtering rates considered elevated by slow filtering treatment standards (9 m3.m-2.d-1). Therefore, it concludes that the filter medium constituted exclusively of 25-cm-thick non-woven synthetic fabric has the potential to substitute sand in slow-filtering water treatment once it has obtained similar performance to the slow sand filter / Doutorado / Agua e Solo / Doutora em Engenharia Agrícola