A presente pesquisa avaliou duas alternativas para a remoção de fósforo em esgoto sanitário: uso de filtros percoladores com adição de material com potencial de ligação de fósforo e uso de banhados construídos com macrófitas com potencial assimilação de fósforo. Estas tecnologias são apropriadas para pequenas comunidades ou residências unifamiliares e também podem ser utilizadas como etapa no tratamento dos esgotos. Estes sistemas apresentam remoção satisfatória de matéria orgânica e nitrogênio amoniacal, contudo apresentam diminuta eficiência de remoção de fósforo e nitrato. Na presente pesquisa foram estudadas duas técnicas para aumentar a remoção de fósforo: utilização de materiais com potencial de remoção de fósforo nos filtros percoladores, e plantas com alta capacidade de assimilação de fósforo nos banhados construídos. Os materiais adicionados aos leitos percoladores com potencial de remoção de fósforo foram: Cavaco de Usinagem e Escória de Aciaria Elétrica. As frações de materiais adicionados foram: 10%, 20% e 40% em peso em relação ao material suporte. As plantas utilizadas foram a Luziola peruviana, a qual apresenta em sua constituição alta concentração de fósforo e a Typha latifolia, já amplamente utilizada em banhados construídos. Os materiais utilizados como meios suportes foram brita e areia. A adição de materiais com potencial remoção de fósforo auxiliou na remoção do nutriente, a qual foi mais significativa nos leitos contendo Cavaco de Usinagem. Não foi observada diferença de remoção de fósforo para as diferentes frações dos materiais testados para o período de estudo. A utilização da planta Luziola peruviana contribuiu no máximo com 2,11% da remoção de fósforo total, contudo foi observada importante função do sistema radicular no tempo de percolação, contribuindo para maior tempo de contato do efluente com material suporte, especialmente para o caso da brita. O uso de areia de granulometria grossa possibilitou eficiência de remoção de fósforo superior a 85%, entretanto, a massa de fósforo retida por unidade de área no sistema utilizando brita 0 apresentou valores duas vezes superiores aos obtidos para os leitos preenchidos com areia. / This research evaluated two alternatives to phosphorus removal from domestic wastewater: use of intermittent sand filters with materials addition with potential phosphorus binding and use of constructed wetlands with macrophytes potential phosphorus assimilation. These present themselves as technologies suitable for small communities or single family houses and can be used as a intermediate or final stage of wastewater treatment. The systems based on intermittent feed get satisfactory removal of organic matter and ammonia-N, but they have reduced efficiency of phosphorus and nitrate removal. The aim of present study was to evaluate two techniques for phosphorus removal: use of materials with potential removal of phosphorus, in the intermittent sand filters, and plants with capacity for assimilation of phosphorus metabolism, in the vertical flow constructed wetlands. The materials added to the sand filters with the potential removal of phosphorus were the Machine Bit and Electric Arc Furnace Slag. The fractions of materials added were: 10%, 20% and 40% related to material support weight. The plants tested were Luziola peruviana, which has in its constitution a high concentration of phosphorus and Typha latifolia, widely used in constructed wetlands. The support materials tested were gravel and sand. The use of materials with potential removal of phosphorus aid in the removal of phosphorus, which is more significant in the beds with Machine Bit. Difference of phosphorus removal was not observed for the different fractions of the materials tested for the study period. The use of the plant Luziola peruviana contributed at the most with 2,11% of removal of total phosphorus, however important role of the root system was observed in the percolation time, contributing to larger time of contact of wastewater with support materials, especially for use of coarse material, as it the coarse gravel. The use of coarse sand allowed removal efficiency of phosphorus higher than 85%, however, the mass of phosphorus retained per unit area in the system using gravel present values twice higher than obtained to the beds filled with sand.

A presente pesquisa avaliou duas alternativas para a remoção de fósforo em esgoto sanitário: uso de filtros percoladores com adição de material com potencial de ligação de fósforo e uso de banhados construídos com macrófitas com potencial assimilação de fósforo. Estas tecnologias são apropriadas para pequenas comunidades ou residências unifamiliares e também podem ser utilizadas como etapa no tratamento dos esgotos. Estes sistemas apresentam remoção satisfatória de matéria orgânica e nitrogênio amoniacal, contudo apresentam diminuta eficiência de remoção de fósforo e nitrato. Na presente pesquisa foram estudadas duas técnicas para aumentar a remoção de fósforo: utilização de materiais com potencial de remoção de fósforo nos filtros percoladores, e plantas com alta capacidade de assimilação de fósforo nos banhados construídos. Os materiais adicionados aos leitos percoladores com potencial de remoção de fósforo foram: Cavaco de Usinagem e Escória de Aciaria Elétrica. As frações de materiais adicionados foram: 10%, 20% e 40% em peso em relação ao material suporte. As plantas utilizadas foram a Luziola peruviana, a qual apresenta em sua constituição alta concentração de fósforo e a Typha latifolia, já amplamente utilizada em banhados construídos. Os materiais utilizados como meios suportes foram brita e areia. A adição de materiais com potencial remoção de fósforo auxiliou na remoção do nutriente, a qual foi mais significativa nos leitos contendo Cavaco de Usinagem. Não foi observada diferença de remoção de fósforo para as diferentes frações dos materiais testados para o período de estudo. A utilização da planta Luziola peruviana contribuiu no máximo com 2,11% da remoção de fósforo total, contudo foi observada importante função do sistema radicular no tempo de percolação, contribuindo para maior tempo de contato do efluente com material suporte, especialmente para o caso da brita. O uso de areia de granulometria grossa possibilitou eficiência de remoção de fósforo superior a 85%, entretanto, a massa de fósforo retida por unidade de área no sistema utilizando brita 0 apresentou valores duas vezes superiores aos obtidos para os leitos preenchidos com areia. / This research evaluated two alternatives to phosphorus removal from domestic wastewater: use of intermittent sand filters with materials addition with potential phosphorus binding and use of constructed wetlands with macrophytes potential phosphorus assimilation. These present themselves as technologies suitable for small communities or single family houses and can be used as a intermediate or final stage of wastewater treatment. The systems based on intermittent feed get satisfactory removal of organic matter and ammonia-N, but they have reduced efficiency of phosphorus and nitrate removal. The aim of present study was to evaluate two techniques for phosphorus removal: use of materials with potential removal of phosphorus, in the intermittent sand filters, and plants with capacity for assimilation of phosphorus metabolism, in the vertical flow constructed wetlands. The materials added to the sand filters with the potential removal of phosphorus were the Machine Bit and Electric Arc Furnace Slag. The fractions of materials added were: 10%, 20% and 40% related to material support weight. The plants tested were Luziola peruviana, which has in its constitution a high concentration of phosphorus and Typha latifolia, widely used in constructed wetlands. The support materials tested were gravel and sand. The use of materials with potential removal of phosphorus aid in the removal of phosphorus, which is more significant in the beds with Machine Bit. Difference of phosphorus removal was not observed for the different fractions of the materials tested for the study period. The use of the plant Luziola peruviana contributed at the most with 2,11% of removal of total phosphorus, however important role of the root system was observed in the percolation time, contributing to larger time of contact of wastewater with support materials, especially for use of coarse material, as it the coarse gravel. The use of coarse sand allowed removal efficiency of phosphorus higher than 85%, however, the mass of phosphorus retained per unit area in the system using gravel present values twice higher than obtained to the beds filled with sand.

A presente pesquisa avaliou duas alternativas para a remoção de fósforo em esgoto sanitário: uso de filtros percoladores com adição de material com potencial de ligação de fósforo e uso de banhados construídos com macrófitas com potencial assimilação de fósforo. Estas tecnologias são apropriadas para pequenas comunidades ou residências unifamiliares e também podem ser utilizadas como etapa no tratamento dos esgotos. Estes sistemas apresentam remoção satisfatória de matéria orgânica e nitrogênio amoniacal, contudo apresentam diminuta eficiência de remoção de fósforo e nitrato. Na presente pesquisa foram estudadas duas técnicas para aumentar a remoção de fósforo: utilização de materiais com potencial de remoção de fósforo nos filtros percoladores, e plantas com alta capacidade de assimilação de fósforo nos banhados construídos. Os materiais adicionados aos leitos percoladores com potencial de remoção de fósforo foram: Cavaco de Usinagem e Escória de Aciaria Elétrica. As frações de materiais adicionados foram: 10%, 20% e 40% em peso em relação ao material suporte. As plantas utilizadas foram a Luziola peruviana, a qual apresenta em sua constituição alta concentração de fósforo e a Typha latifolia, já amplamente utilizada em banhados construídos. Os materiais utilizados como meios suportes foram brita e areia. A adição de materiais com potencial remoção de fósforo auxiliou na remoção do nutriente, a qual foi mais significativa nos leitos contendo Cavaco de Usinagem. Não foi observada diferença de remoção de fósforo para as diferentes frações dos materiais testados para o período de estudo. A utilização da planta Luziola peruviana contribuiu no máximo com 2,11% da remoção de fósforo total, contudo foi observada importante função do sistema radicular no tempo de percolação, contribuindo para maior tempo de contato do efluente com material suporte, especialmente para o caso da brita. O uso de areia de granulometria grossa possibilitou eficiência de remoção de fósforo superior a 85%, entretanto, a massa de fósforo retida por unidade de área no sistema utilizando brita 0 apresentou valores duas vezes superiores aos obtidos para os leitos preenchidos com areia. / This research evaluated two alternatives to phosphorus removal from domestic wastewater: use of intermittent sand filters with materials addition with potential phosphorus binding and use of constructed wetlands with macrophytes potential phosphorus assimilation. These present themselves as technologies suitable for small communities or single family houses and can be used as a intermediate or final stage of wastewater treatment. The systems based on intermittent feed get satisfactory removal of organic matter and ammonia-N, but they have reduced efficiency of phosphorus and nitrate removal. The aim of present study was to evaluate two techniques for phosphorus removal: use of materials with potential removal of phosphorus, in the intermittent sand filters, and plants with capacity for assimilation of phosphorus metabolism, in the vertical flow constructed wetlands. The materials added to the sand filters with the potential removal of phosphorus were the Machine Bit and Electric Arc Furnace Slag. The fractions of materials added were: 10%, 20% and 40% related to material support weight. The plants tested were Luziola peruviana, which has in its constitution a high concentration of phosphorus and Typha latifolia, widely used in constructed wetlands. The support materials tested were gravel and sand. The use of materials with potential removal of phosphorus aid in the removal of phosphorus, which is more significant in the beds with Machine Bit. Difference of phosphorus removal was not observed for the different fractions of the materials tested for the study period. The use of the plant Luziola peruviana contributed at the most with 2,11% of removal of total phosphorus, however important role of the root system was observed in the percolation time, contributing to larger time of contact of wastewater with support materials, especially for use of coarse material, as it the coarse gravel. The use of coarse sand allowed removal efficiency of phosphorus higher than 85%, however, the mass of phosphorus retained per unit area in the system using gravel present values twice higher than obtained to the beds filled with sand.

Orientador: Sergio Nascimento Bordalo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-13T17:08:45Z (GMT). No. of bitstreams: 1 Silva_ElinaldoSantos_M.pdf: 5134236 bytes, checksum: 2676ce4cb7784fed1bc7b1d622f6cc62 (MD5) Previous issue date: 2006 / Resumo: O escoamento vertical bifásico é de suma importância na produção de petróleo, uma vez que os reservatórios petrolíferos produzem óleo e gás simultaneamente, e estes devem fluir até a superfície submarina através de poços, e destes até a plataforma de produção através de dutos verticais (risers) no mar. Ao longo de seu escoamento, a mistura pode desenvolver vários padrões de fluxo. Os padrões identificados no escoamento vertical são bolhas, golfadas, transição e anular, e essas configurações físicas apresentam características próprias que exigem modelagens distintas, apresentando relações particulares de perda de carga em função da vazão. A caracterização correta do padrão, sob dadas condições operacionais, é fundamental para modelar a dinâmica do escoamento e determinar a relação entre perda de carga e vazão. Na literatura, estudos sobre o estabelecimento dos padrões de fluxo foram realizados com água e ar, e estão restritos ao caso de dutos estáticos, enquanto que os risers de produção estão em constante movimento devido à ação das ondas, das correntezas e da plataforma de produção. Sendo assim, a aplicação destes mapas nas condições de produção em águas profundas são questionáveis. O presente trabalho é importante para a produção de óleo e gás em águas profundas, porque aborda as condições de movimento de dutos verticais longos e esbeltos sob oscilações. Nestes dutos, as forças decorrentes do movimento do mar e da plataforma de produção geram sobre o duto um movimento transversal alternado. Para se estudar esse efeito, um aparato experimental foi construído em escala de laboratório, com um duto flexível de 8,0 m de comprimento e 25,4 mm de diâmetro, provido de um sistema de oscilação e de injeção de água e ar para se estudar os padrões de fluxo vertical ascendente bifásico em dutos em movimento. / Abstract: The two-phase vertical flow is of utmost importance for petroleum production, since petroleum reservoirs produce oil and gas simultaneously, which must flow up to the undersea surface through wells, and from these to the production platform through vertical pipes (risers) in the sea. Throughout the flow, the mixture of oil and gas may develop several flow patterns. The flow patterns identified in the vertical flow are bubbles, slugs, churn and annular, and these physical configurations present specific characteristics that demand distinct modeling and, presenting particular relations of head loss as function of the flow rate. The correct characterization of the flow patterns, under given operational conditions, is fundamental to the modeling of the dynamics of the flow and to determine the relation between head loss and flow rate. In the literature, studies on the establishment of the flow patterns had been carried with water and air, and were restricted to the case of static pipes, while production risers are in constant movement due to the action of waves, sea currents and the displacement of the production platform. Therefore, the application of these static maps for the conditions of production in deep waters is questionable. The present work is important for the production of oil and gas in deep waters, because it takes into account the oscillatory movement of long and slender vertical pipelines. In these pipes, the forces resulting from of the movements of the sea and the production platform generate an alternated transversal movement on the pipeline. An experimental apparatus built in the laboratory scale to study this effect, with a flexible duct of 8,0 m of length and 25,4 mm of diameter, attached to a system of oscillation and connected to an injection nozzle of water and air to study the patterns of two-phase vertical upward flow in moving pipes. / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

The ways of purifying waste water produced by human society are nowadays a great deal. With the increasing pressure on sustainable construction, technology using principles close to natural processes are at the forefront. Treatment wetlands have been in use for almost 30 years and thanks mainly to developments abroad, they prove they are a suitable option for smaller producers of pollution. When designing a treatment wetland for municipalities with a larger amount of inhabitants, it is necessary to modify the proposal in order to eliminate all types of pollution. This thesis therefore compares three sewage treatment plants with a multistage filtration system. Comparing the achieved parameters will be beneficial for defining the rules for optimal design of these types of wastewater treatment plant.

Subject of this thesis is ecologic wastewater treatment with little organic load. Treated wastewater for infiltration must contain low values of nitrogen. This thesis is about to design two-stage subsurface vertical flow constructed wetland.

Les filtres plantés de roseaux à écoulement vertical (FPR-V) pour le traitement des eaux usées domestiques sont relativement bien développés en France et permettent de réaliser un traitement poussé de la matière carbonée et la nitrification. La robustesse de cette filière réside également dans sa capacité à accepter des surcharges hydrauliques en temps de pluie. Cependant ces limites d’acceptation hydraulique ne sont pas bien définies et demandent à être optimisées. La conception des FPR-V pour accepter des surcharges hydrauliques est un travail complexe car le contexte local affecte fortement les débits d’eau entrants dans la station lors d’un événement pluvieux. Dans de tels cas, la conception de filtres demande l’utilisation de modèles dynamiques. Ces modèles s’appuient le plus souvent sur une approche mécanistique et sont à l'origine conçus et utilisés pour la recherche. Cependant, si ces modèles sont des outils puissants pour décrire en détail la dynamique du FPR-V, ils sont généralement trop complexes à manipuler pour des utilisateurs non experts. Choisir entre une description détaillée et une manipulation facile dépendra des objectifs de modélisation. Quand des objectifs de dimensionnement global sont visés par les concepteurs, l'utilisation de modèles simplifiés semble une bonne alternative. Les modèles simplifiés sont faciles à utiliser pour la conception de FPR-V mais ils sont peu nombreux. Cependant ils sont adaptés à des configurations spécifiques liées au traitement des surverses de déversoirs d’orage, ce qui n’est pas le cas pour les FPR-V traitant des eaux usées domestiques. En effet, pour ce type de FPR-V les vitesses d’infiltration du système varient considérablement. En conséquence, ce travail de thèse a pour objectif de développer un modèle hydraulique simplifié des FPR-V qui permettra de guider les concepteurs dans le processus d’adaptation des FPR-V pour traiter les eaux usées domestiques des périodes de temps sec et de temps de pluie. Le modèle simplifié permet de relier (i) l’hydraulique du filtre, en simulant le temps de noyage à la surface, et (ii) les performances biologiques, en établissant des «alertes de dysfonctionnement », basées sur l'évaluation des performances épuratoires et sur les variations des formes azotées à la sortie du filtre mesurées en continu. Les «alertes de dysfonctionnement» représentent la charge hydraulique maximale qu'un filtre peut accepter sans compromettre son activité biologique. Le modèle simplifié a été utilisé pour la modélisation hydraulique du FPR-V à long terme (i) pour analyser l’impact du contexte local et la conception du filtre dans l’acceptation de surcharges hydrauliques. Grâce à cet analyse, (ii) on peut proposer les dimensionnements de FPR-V qui arrivent à mieux gérer l’acceptation des surcharges hydrauliques. / French vertical-flow constructed wetlands (VFCW) directly treating raw wastewater are known to perform well on for SS, COD and nitrification. They are also known to robustly cope with hydraulic overloads during rainfall events. Although numerous systems have been installed in areas equipped with a combined sewer, the limits of stormwater acceptance remain ill-defined and need to be improved. Looking at the various VFCW designs and usages reported in the literature, it is difficult to draw any consensus on their hydraulic limits. Consequently, designing VFCW to accept hydraulic overloads is a complex task, as local context strongly impacts inlet flows produced during rainfall events. Dynamic models appear a requisite for filter design in such cases. Numerical CW models have essentially focused on horizontal flow, with few attempting to study VFCW dynamics which are more commonly tackled via mechanistic models. Although mechanistic models are powerful tools for describing processes within the VFCW, they are generally too complicated to be readily used by designers. The choice between detailed description and easy handling will depend on the modelling aims. If the aim is a global design tool, simplified models offer a good alternative. However, the simplified models geared to studying VFCW dynamics are extremely reduced. They are easy-handling for design and well-adapted to specific purposes (combined sewer overflow -CSO- treatment) but not necessarily to VFCW treating combined sewer wastewater, where long-term infiltration rates vary significantly. Consequently, this PhD thesis work focused on developing a simplified hydraulic model of VFCW to guide designers through the process of adapting VFCW systems to treat domestic wastewater in both dry and rain events. The simplified model makes it possible to link (i) hydraulics, by simulation of ponding time variations, (ii) biological performances, by establishing “dysfunction alerts” based on treatment performance assessment and variations in online N forms effluent from the young VFCW. These “dysfunction alerts” plot the maximal hydraulic load that a filter can accept without compromising its biological activity. The simplified model was used to model long-term hydraulics in the VFCW (i) to analyze the impact of local context and filter design on hydraulic overload acceptance (using “dysfunction alerts” and bypass discharges) and (ii) to propose VFCW designs for accepting hydraulic overload in different contexts. The modelling demonstrates that VFCW can limit days with bypass discharges to less than 20 times per year without jeopardizing filter performances. Moreover, the most problematic scenario on stormwater treatment remains a watershed with high imperviousness coefficient and low slope under a Bretagne-type climate, demonstrating that the filter is more sensitive to periodicity and duration than to intensity of rainfall events.

The constantly tightening wastewater treatment legislation require high-quality runoff from small-scale producers of pollution who are typically represented by small municipalities up to 500 inhabitants or decentralized parts of larger municipalities. Small municipalities are faced with high investment-intensity associated with the acquisition of new wastewater treatment plant. After several years of development, today natural technologies of wastewater treatment are in competition with mechanical-biological treatment plants. Natural technologies can even achieve better results than popular biological treatment plants. However, natural technology does not eliminate the main investment limit connected with the acquisition of wastewater treatment plant. If there was cheaper solution connected with using alternative filter materials (in our case recycled construction and demolition waste), small municipalities could take constructed wetland without large subsides. At the same time, the use of recycled construction and demolition wastes will lead to benefits in the field of sustainable urban development and replacement of non-renewable materials. Despite these benefits, recycled aggregates have never been considered as alternative filter materials for natural wastewater treatment plants. For that reason, the aim of diploma thesis is to assess the possibility of applying recycled aggregates for wastewater treatment which will include evaluation of real trial operation.

An experimental study was carried out to evaluate the performance of pilot scale constructed wetlands for the treatment of domestic wastewater in Addis Ababa, Ethiopia. Three parallel sets of constructed wetlands; consisting of one Horizontal Flow (HF), one Vertical Flow (VF) and one hybrid of HF and VFconstructed in series were built in Addis Ababa. The wetland systems had identical wetland fill media and macrophytes but with different wastewater flow types. The total surface area of the wetland systems was 72 m2 /24 m2 for each/ and designed to treat 3.15 m3 of domestic wastewater per day. Triplicate grab samples were taken from the influent and effluents every 15 days for one year and analyzed within 24 hours. Temperature, pH, DO and EC were measured onsite and the nutrient content of macrophytes was determined twice during the monitoring period. During the first 12 months monitoring period, the average removal efficiencies of the HFCW, VFCW and hybrid CW were: BOD (89.1%, 92.2% and 93.4%), COD (80.6%, 82.1% and 84.0%), TSS (89.1, 83.8% and 84.7%), NH4 + (58.6%, 66.2% and 65.4%), NO3 - (64.0%, 71.5% and 73.5%), TN (49.1%, 54.9% and 58.7%), PO4 3- (45.4%, 50.3% and 48.4%), TP (58.0%, 51.7% and 54.4%) and FC (98.6%, 96.6% and 96.5%), respectively. The hybrid system showed relatively higher removal efficiencies for most pollutants. Again, the wetland systems showed relatively higher percent reduction during the dry seasons /from Dec - May/. The areal removal rate constants of BOD5, TN, PO4 3- and TP were higher than the literature values while the values of COD and TSS were lower compared to the literature values. Concerning the nutrient content of the wetland plant, the average TN contents of the below-ground and above-ground plant part were 1.56% and 2.27% for the HFCW, 1.75% and 2.74% for the VFCW and 1.80% and 2.63% for the hybrid system, respectively. Meanwhile, the average TP contents of the belowground and above-ground plant part were 0.139% and 0.064% for the HFCW, 0.167% and 0.067% for the VFCW and 0.115% and 0.065% for the hybrid systems, respectively. In general, the results showed that properly designed constructed wetland systems could be used as effective wastewater treatment method in Ethiopia. / Environmental Sciences / Ph. D. (Environmental Sciences)

Dans les filtres plantés de roseaux à écoulement vertical, la percolation des eaux usées à travers le milieu filtrant entraine la rétention physique des matières en suspension à la surface des filtres, et leur accumulation conduit à la formation d’une couche de boue principalement sur le premier étage des filtres. Longtemps considérée comme un facteur de risque de colmatage, cette couche de surface est aussi un compartiment majeur de la performance du système. Dans l’objectif de mieux connaitre la nature et l’évolution des dépôts qui la constituent, des échantillons issus de 14 stations en fonctionnement ont été prélevés pour analyser notamment la nature de leur matière organique particulaire et son évolution. Les résultats ont montré que les dépôts de stations de plus de trois ans de fonctionnement tendent vers un état similaire, caractérisé par la présence de composés organiques stables et complexes et par une plus faible réactivité de la matière organique particulaire. Les dépôts provenant de stations de moins d’un an de fonctionnement présentent une signature particulière, caractérisée par une matière organique réactive et peu mature. En complément de cette évolution en surface du filtre, la matière organique particulaire des eaux usées entrantes peut également subir des modifications au sein du process d’un filtre planté de roseaux. La présence d’un lit bactérien comme traitement additionnel participe à l’hydrolyse et à la transformation de la matière organique particulaire par des processus de minéralisation et d’humification. L’ajout de chlorure ferrique favorise l’agrégation de la matière. Enfin, des polluants organiques et métalliques d’intérêt ont fait l’objet d’une première quantification dans ces dépôts afin d’estimer leur rétention pour mieux appréhender les risques potentiels en cas de dysfonctionnement ou d’épandage. L’étude du comportement à la lixiviation en fonction du pH a permis de mettre en évidence que la libération de certains éléments traces est liée à celle de la matière organique. / The percolation of unsettled wastewater in French Vertical Flow Constructed Wetlands (VFCWs) causes the formation of a sludge layer at the surface of the first stage filter due to the retention of sludge deposits. Although the growth of this layer over the years of operation is a potential source of clogging risks, it also largely contributes in the performance of the system, depending on its properties. In order to better understand these phenomena, surface sludge deposits samples taken from 14 VFCW sewage treatment plants were collected and analyzed. Results showed that the structure and composition of the sludge deposits from treatment plants with more than three years of operation time were remarkably similar, characterized by the presence of stable and complex organic compounds and a low reactivity and biodegradability of the particulate organic matter. Deposits from treatment plants with less than one year of operation time were composed of more reactive and less mature organic matter. The particulate organic matter of the inflow wastewater was also shown to undergo modifications within the treatment chain of the vertical flow constructed wetland. The implementation of a biological trickling filter as an additional treatment prior to the filter stages was found to induce the transformation of soluble and particulate organic matter through mineralization and hydrolysis, and to contribute to humification probably by the detachment of biofilm fragments. The injection of ferric chloride used to precipitate phosphates was found to promote aggregation within the sludge deposits. Finally, the role of the sludge layer in the retention of a selection of organic and metallic pollutants in VFCW systems has been evaluated by analyzing sludge deposits samples. Detergents were found at higher concentrations than PCPP. The potential release of the sorbed contaminants was studied using leaching tests as a function of pH. Results showed that the release of some trace metals (mostly copper) was governed by the leaching behavior of organic matter.