Vacuum dewatering of paper is a heavily energy expensive process, even more so for greaseproof paper, which is one of the main products at Nordic Paper Seffle AB. Due to this being such an energy demanding process, improvements in the vacuum dewatering could save massive amounts of energy. The focus of this thesis is to investigate the effect of a triple vacuum suction box on the dewatering rate of greaseproof paper, using a tried and tested method of simulative triple vacuum suction box at a laboratory scale, with the difference of simulating a quadruple vacuum suction box, and how the grammage of the paper sheet affected this, using unbleached sulphate pulp consisting of soft wood with an addition of 20 % eucalyptus fibers. The results were as expected, showing the expected dryness curve behavior of diminishing returns of the dryness to dwell time ratio, and the method showed valid for improving the energy efficiency compared to a single vacuum suction box, in terms of both expended energy, and yielded dryness. The grammage had a significant effect on the dewatering, with the heavier paper at 100 gsm showing the need of higher dwell times and increased levels of vacuum pressure than the lighter paper at 50 gsm. An addition of a triple vacuum suction box could possibly replace multiple high vacuum suction boxes, leading to even greater savings. Further testing would be required for optimization of the vacuum levels and dwell times for the 100 gsm paper sheet, in order to reach the same dryness as the 50 gsm paper sheet. / Vakuumavvattning av papper är en mycket energikrävande process, ännu mer för greaseproofpapper, som är en av huvudprodukterna hos Nordic Paper Seffle AB. Eftersom detta är en så energikrävande process kan förbättringar av vakuumavvattningen spara enorma mängder energi. Fokus för denna avhandling är att undersöka effekten av en trippelvakuumsuglåda på avvattningseffektiviteten av greaseproofpapper, med hjälp av en beprövad metod för simulativ trippelvakuumsuglåda i laboratorieskala, med skillnaden att simulera en fyrdubbelvakuumsuglåda, och hur ytvikten på pappersarket påverkar detta; med oblekt sulfatmassa bestående av långfiber med tillsats av 20 % eukalyptusfibrer. Resultaten var som förväntat och visade den förväntade torrhaltskurvans beteende av avtagande förbättring av torrhalten, och metoden visade sig vara giltig för att förbättra energieffektiviteten jämfört med en enda vakuumsuglåda, både vad gäller förbrukad energi och torrhalt. Ytvikten hade en stor effekt på avvattningen, där det tyngre papperet på 100 gsm visade behov av längre uppehållstider och ökade nivåer av vakuumtryck än det lättare papperet vid 50 gsm. Ett tillägg av en trippelvakuumsuglåda kan troligen ersätta flera högvakuumsugslådor, vilket leder till ännu större besparingar. Ytterligare tester skulle krävas för optimering av vakuumnivåerna och uppehållstiderna för 100 gsm pappersarket, för att nå samma torrhet som 50 gsm pappersarket.

Cellulose nanofibrils (CNF) is a renewable material with unique strength properties. A difficulty in CNF production is that CNF suspensions contain large amounts of water. If CNF suspension volume can be decreased by dewatering facilitated by centrifugation, then transportation costs and storage costs can be reduced. The aim of this thesis is to investigate the impact various parameters have on CNF centrifugation dewatering and identify optimal conditions for maximal water removal. A laboratory study was conducted using four materials; 2.0 w% enzymatically treated CNF (CNF1), 1.9 w% carboxymethylated CNF (CNF2) and two commercial samples (1.9 w% CNFA and 1.8 w% CNFB). The main method was analytical centrifugation up to 2330 g. Parameters tested were initial concentration before centrifugation, temperature, NaCl addition, pH, and applied solid compressive pressure (g-force and surface weight). In addition to centrifugation experiments the four materials were characterized with laser diffraction, UV-vis absorption, Dynamic light scattering, and dry weight measurements. Analysis of the experimental data collected show that increase in initial concentration give a higher final concentration, but less water is removed. Furthermore, temperature changes have no effect on separation of CNF and water. At an applied solid compressive pressure of 3 kPa and initial concentration at 1.5 w% the concentrations 5.5 w%, 1.5 w%, 4.0 w%, and 4.3 w% can be reach for CNF1, CNF2, CNFA, and CNFB respectively. After extrapolation of polynomial functions fitted to experimental data an applied solid compressive pressure of 22 kPa and initial concentration at 1:5 w%, the concentrations 9.1 w%, 1.5 w%, 6.9 w%, and 7.9 w% are predicted for CNF1, CNF2, CNFA, and CNFB respectively. The thickening of CNF suspensions achieved and predicted in this thesis implies possibilities for large amounts of water removal, e.g. the water content in a CNF1 suspension is reduced from 65.7 litres/kg CNF to 10.0 litres/kg CNF at the solid compressive pressure 22 kPa. The concentrations at 22 kPa are determined by extrapolation from experimental data <3 kPa solid compressive pressure. The carboxymethylated CNF2 can not be dewatered unless it is diluted or if salt or pH is adjusted. This is directly correlated to the electrostatic forces in the suspension and the Debye length. Addition of salt or lowered pH also eliminate any concentration gradients in diluted and centrifuged CNF2 suspensions. / Cellulosa nanofibriller (CNF) är ett förnybart material med unika styrkeegenskaper. En svårighet med produktion av CNF är att CNF suspensioner innehåller stora mängder vatten. Om volymerna av CNF suspensioner kan minskas med avvattning genom centrifugering, då kan transport- och lagerkostnader sänkas. Målet med det här examensarbetet är att undersöka vilken inverkan olika parametrar har på CNF-avvattning genom centrifugering och identifiera optimala förhållanden för maximalt avlägsnande av vatten. En laboratoriestudie utfördes på fyra olika material. De fyra materialen är 2 w% enzymatiskt behandlad CNF (CNF1), 1.9 w% karboxymetylerad CNF (CNF2) och två kommersiella prover (1.9 w% CNFA och 1.8 w% CNFB). Den huvudsakliga metoden var analytisk centrifugering upp till maximalt 2330 g. De testade parametrarna var initial koncentration innan centrifugering, temperatur, NaCl tillsats, pH, och applicerat fast kompressionstryck (g-kraft och ytvikt). Förutom centrifugeringsexperimenten så karaktäriserades the fyra mmaterialen med laser diffraktion, UV-vis absorption, dynamisk ljusspridning och vägningar av torrhalt. Analys av den experimentella data som insamlats visar att en ökad initial koncentration ger en högre slutkoncnentration, men mindre vatten kan bortföras. Temperaturförändringar har ingen effekt på separation av CNF och vatten. Vid ett applicerat fast kompressibelt tryck på 3 kPa och en initial koncentration 1.5 w% kan koncentrationerna 5.5 w%, 1.5 w%, 4.0 w%, och 4.3 w% nås för CNF1, CNF2, CNFA, och CNFB. Efter extrapolering av polynoma funktioner passad till experimentell data förutspås att koncentrationerna 9.1 w%, 1.5 w%, 6.9 w%, och 7.9 w% kan nås för CNF1, CNF2, CNFA, and CNFB vid 22 kPa och en initial koncentration på 1.5 w%. Förtjockningen av CNF suspensioner som kan, eller förutspås kunna nås genom centrifugering i det här examensarbetet innebär att det är möjligt att avlägsna stora mängder vatten, till exempel kan vatteninnehållet i CNF1 minskas från 65.7 liter/kg CNF till 10.0 liter/kg CNF vid 22 kPa fast kompressionstryck. Koncentrationerna vid 22 kPa fast kompressionstryck är extrapolerade från exprimentell data <3 kPa fast kompressionstryck. Den karboy- metylerade CNF2 kan inte avvattnas om den inte späds ut eller om salt eller pH justeras. Detta är direkt kopplat till de elektrostatiska krafterna i suspensionen och Debye längden. Tillsats av salt eller sänkt pH eliminerar också de koncentrationsgradienter som kan förekomma i utspädda centrifugerade CNF2 suspensioner.

This thesis focuses on modeling the primary sludge in the thickening process at Henrikdals wastewater treatment plant in Stockholm, Sweden. The thickening process is one of the core processes at the wastewater treatment plant, where the goal is to thicken a residual product called primary sludge. Two thickener belts are used to thicken the sludge gravimetrically. Polymer is also added to increase the dewaterability and to thicken the sludge. The thickness of the sludge is measured by the total solids content (TS) in the sludge and is measured with total solid measurement sensors. These sensors have, however, been shown to be inaccurate. A long short-term memory network (LSTM) and a feed-forward neural network were compared by using sensor and instrument data to predict the TS in the thickened primary sludge. To validate the performance of the models, manual laboratory testing samples were compared with the predictions of the models. Simulations in Simulink were also performed with the intent of simulating the thickening process. By using a machine learning model that could predict the TS, hypotheses regarding reductions in the polymer dosage were explored. A feed-forward and feedback control strategy in combination with the LSTM architecture were used and it was shown that the TS of the thickened sludge could be controlled by regulating the polymer dosage. Thus, using a feedback control strategy gives further opportunities for the wastewater treatment plant to choose whether a lower polymer consumption or a higher TS is preferred, as these two variables correlate with each other. / Syftet med detta arbete var att ta fram maskininlärningsmodeller av primärslamsförtjockningen på Henriksdals avloppsreningsverk i Stockholm, Sverige. Förtjockningsprocessen är en av de viktigaste delerna i avloppsreningsverk, där målet är att förtjocka en restprodukt som kallas primärslam. Förtjockningen sker i två separata linjer. Polymer tillsätts och slammet förtjockas genom gravimetrisk avvattning på ett silband. Slammets torrsubstanshalt (TS) är ett mått på slammets tjockhet och beräknas med hjälp av att använda sensorer. Dessa sensorer har dock visats sig vara opålitliga. Genom att använda tillgänglig process-, maskin- och instrumentdata så har en long short-term memory (LSTM) arkitektur och ett framkopplat neuralt nätverk jämförts för att uppskatta torrsubstansen i primärslammet. Manuell provtagning och labbanalys utfördes för att validera prestandan i de två modellerna. Hypoteser kring att kunna optimera TS-halten eller minska polymerförbrukningen utforskades genom att simulera processen i Simulink. Resultaten visade att användandet av en fram och återkopplingsregulator tillsammans med en LSTM arkitektur kan minska polymerförbrukningen och kan ge en jämnare TS-halt i det förtjockade slammet. Däremot måste en avvägning mellan hög TS-halt och låg polymerförbrukning göras, då dessa två variabler korrelerar med varandra

Cellulose Nano Fibrils (CNFs) can be extracted from wood and other plants. These CNFs are expected to play a large roll in future materials owing to their interesting properties and biobased nature. In this project, dewatering of gels made from CNF by non-confined mechanical pressing has been studied. A CNF suspension was gelled by the addition of HCl at pH 2 to form gel cakes and then pressed mechanically. The goal was to find the pressure limits of the gel cakes for different starting concentrations, in weight percentage [wt%], of CNF to optimize the pressure used when dewatering CNF gels. The non-confined pressing was achieved via the useof a Zwick/Roell Torsion multi-axis testing system. Gel cakes were pressed until a pressing equilibrium was reached. Equilibrium was reached when compression was less than 0.01 mm per 100 seconds. Gel cakes were frozen with liquid N2, freeze-dried, and analysed with Scanning Electron Microscopy (SEM). The results observed from the pressing data showed that gel cakes with higher CNF starting concentrations could survive higher pressures. Using the highest pressure available, at the pressure limit, yielded both the shortest run time and the highest dryness content. SEM imaging showed that the compression of the gel cakes starts at the surfaces and continuous inwards through the bulk. The mechanical pressure creates sheets of CNF both vertically and horizontally. By plotting the starting concentrations vs applied pressure a limit map with pressure regions could be created. From the limit map further optimization can be achieved to shorten the dewatering process of the CNF gels.

In the present work, novel dewatering aids and a novel centrifuge configuration were developed and applied for the purpose of dewatering fine particles. Three different types dewatering reagents were tested in different filtration and centrifugation units. These chemicals included low-HLB surfactants, naturally occurring lipids, and modified lipids. Most of these reagents are insoluble in water; therefore, they were used in solutions of appropriate solvents, such as light hydrocarbon oils and short-chain alcohols. The role of these reagents was to increase the hydrophobicity of the coal and selected mineral particles (chalcopyrite, sphalerite, galena, talc, clay, phosphate, PCC and silica) for the dewatering. In the presence of these reagents, the water contact angles on the coal samples were increased up to 90o. According to the Laplace equation, an increase in contact angle with the surfactant addition should decrease the capillary pressure in a filter cake, which should in turn increase the rate of dewatering and help reduce the cake moisture. The use of the novel dewatering aids causes a decrease in the surface tension of water and an increase in the porosity of the cake, both of which also contribute to improved dewatering. A series of batch-scale dewatering tests were conducted on a variety of the coal and mineral samples using the novel dewatering aids. The results obtained with a Buchner funnel and air pressure filters showed that cake moistures could be reduced substantially, the extent of which depends on the particle size, cake thickness, drying time, reagent dosage, conditioning time, reagent type, sample aging, water chemistry, etc. It was determined that use of the novel dewatering aids could reduce the cake formation time by a significant degree due to the increased kinetics of dewatering. At the same time, the use of the dewatering aids reduced the cake moistures by allowing the water trapped in smaller capillaries of the filter cake. It was found that final cake moistures could be reduced by 50% of what can be normally achieved without using the reagents. However, the moisture reduction becomes difficult with increasing cake thickness. This problem can be minimized by applying a mechanical vibration to the cake, spraying a short-chain alcohol on the cake and by adding a small amount of an appropriate coagulant, such as alum and CaCl2 to the coal and mineral slurries. The novel dewatering aids were also tested using several different continuous filters, including a drum filter, disc filter and horizontal belt filter (HBF). The results obtained with these continuous filtration devices were consistent with those obtained from the batch filters. Depending on the coal and mineral samples and the type of the reagent, 40 to 60% reductions in moisture were readily achieved. When using vacuum disc filters, the cake thickness increased substantially in the presence of the novel dewatering aids, which could be attributed to the increased kinetics of dewatering. A dual vacuum system was developed in the present work in order to be able to control the cake thickness, which was necessary to achieve lower cake moistures. It was based on using a lower vacuum pressure during the cake formation time, while a full vacuum pressure was used during the drying cycle time. Thus, use of the dual vacuum system allowed the disc filter to be used in conjunction with the novel dewatering aids. Its performance was similar to that of HBF, which is designed to control cake thickness and cake formation time independently. The effectiveness of using the novel dewatering aids were also tested in a full-continuous pilot plant, in which coal samples were cleaned by a flotation column before the flotation product was subjected to the disc filter. The tests were conducted with and without using novel dewatering aids. These results were consistent with those obtained from the laboratory and batch-scale tests. The novel centrifuge developed in the present work was a unit, which combined a gravity force and air pressure. The new centrifuge was based on increasing the pressure drop across the filter cake formed on the surface of the medium (centrifuge wall). This provision made it possible to take advantage of Darcy s law and improve the removal of capillary water, which should help lower the cake moisture. A series of tests were conducted on several fine coal and mineral particles and obtained more than 50% moisture reduction even at very fine particle size (2 mm x 0). Based on the test results obtained in the present work, two proof-of-concept (POC) plants have been designed. The first was for the recovery of cyclone overflows that are currently being discarded in Virginia, and the other was for the recovery of fines from a pond in southern West Virginia. The former was designed based on the results of the plant tests conducted in the present work. Cost vs. benefit analyses were conducted on the two POC plants. The results showed very favorable internal rates of return when using the novel dewatering aids. Surface chemistry studies were conducted on the coal samples based on the results obtained in the present investigation. These consisted mainly of the surface characterization of the coal samples (surface mineral composition, surface area, zeta potential, x-ray photoelectron microscopy (XPS)), acid-base interactions of the solids and liquids, dewatering kinetic tests, contact angle measurements of the coal samples and surface force measurements using AFM. In addition, carbon coating on a silica plate using palsed laser deposition (PLD) and Langmuir-Blodgett (LB) film deposition tests were conducted on the sample to better understand the surfactant adsorption and dewatering processes. The test results showed that the moisture reductions on the fine particles agree well with the surface chemistry results. / Ph. D.

Foi pesquisada a aplicação de métodos, em nível de laboratório, através dos quais é possível otimizar, tratar e dispor resíduos de lavagem de filtros de estações de tratamento de água (Caso ETA do rio Descoberto - ETA-RD Brasília). Na clarificação da água de lavagem dos filtros, observou-se o efeito favorável da adição de polímero para melhorar a separação líquido-sólido é, portanto, as eficiências de remoção de turbidez, cor aparente, sólidos suspensos e coliformes totais. Observou-se melhor sedimentabilidade do lodo a ser desaguado. Os ensaios de centrifugação, em escala de bancada, mostraram que o método aplicado auxilia na determinação da dosagem a ser usada numa centrífuga em escala real. Foram avaliados três métodos de disposição do lodo adensado da ETA-RD em ETE: 1) sedimentação com esgoto sanitário e posterior digestão anaeróbia do lodo; 2) Digestão anaeróbia e 3) digestão aeróbia. Os melhores resultados foram obtidos com a digestão anaeróbia. Os estudos realizados mostraram que há diversas alternativas de tratamento e disposição desses resíduos, mas é necessário, sempre que possível, a avaliação das diferentes alternativas para selecionar a(s) mais apropriada(s) a cada caso em particular, pois fatores como custos e disponibilidade de de sistemas ou equipamentos, definirão a aplicabilidade ou não de determinado método. / It was researched the application of methods on laboratory bench scale to optimize the reuse, treatment and disposal of wastes from filter backwash of Water Treatment Plant - WTP (WTP-RD Descoberto River, Brasília case). In the clarification process of this waste, favorable effect of addition of polymer for best liquid-solid separation and, thus, better removal efficiencies of turbidity, apparent color, suspended solids and total coliforms was observed. Better sedimentability of the sludge occurred. The centrifugation tests showed that the applied method help on determination of dosagem to be used in full scale. Three methods to dispose thickened sludge of WTP-RD on wastewater treatment Plants - WWTP were evaluated: 1) Sedimentation with domestic sewage and anaerobic digestion of sludge; 2) Anaerobic digestion and 3) Aerobic digestion. Best results were obtained with anaerobic digestion. The results showed that there are alternatives of treatment and disposal of wastes of WTP, but is necessary, if possible, to make the evaluation of this alternatives to select the most appropriate(s) in each case because factors as costs, systems or equipments availability, will define the applicability or not of a particular method.

Foi pesquisada a aplicação de métodos, em nível de laboratório, através dos quais é possível otimizar, tratar e dispor resíduos de lavagem de filtros de estações de tratamento de água (Caso ETA do rio Descoberto - ETA-RD Brasília). Na clarificação da água de lavagem dos filtros, observou-se o efeito favorável da adição de polímero para melhorar a separação líquido-sólido é, portanto, as eficiências de remoção de turbidez, cor aparente, sólidos suspensos e coliformes totais. Observou-se melhor sedimentabilidade do lodo a ser desaguado. Os ensaios de centrifugação, em escala de bancada, mostraram que o método aplicado auxilia na determinação da dosagem a ser usada numa centrífuga em escala real. Foram avaliados três métodos de disposição do lodo adensado da ETA-RD em ETE: 1) sedimentação com esgoto sanitário e posterior digestão anaeróbia do lodo; 2) Digestão anaeróbia e 3) digestão aeróbia. Os melhores resultados foram obtidos com a digestão anaeróbia. Os estudos realizados mostraram que há diversas alternativas de tratamento e disposição desses resíduos, mas é necessário, sempre que possível, a avaliação das diferentes alternativas para selecionar a(s) mais apropriada(s) a cada caso em particular, pois fatores como custos e disponibilidade de de sistemas ou equipamentos, definirão a aplicabilidade ou não de determinado método. / It was researched the application of methods on laboratory bench scale to optimize the reuse, treatment and disposal of wastes from filter backwash of Water Treatment Plant - WTP (WTP-RD Descoberto River, Brasília case). In the clarification process of this waste, favorable effect of addition of polymer for best liquid-solid separation and, thus, better removal efficiencies of turbidity, apparent color, suspended solids and total coliforms was observed. Better sedimentability of the sludge occurred. The centrifugation tests showed that the applied method help on determination of dosagem to be used in full scale. Three methods to dispose thickened sludge of WTP-RD on wastewater treatment Plants - WWTP were evaluated: 1) Sedimentation with domestic sewage and anaerobic digestion of sludge; 2) Anaerobic digestion and 3) Aerobic digestion. Best results were obtained with anaerobic digestion. The results showed that there are alternatives of treatment and disposal of wastes of WTP, but is necessary, if possible, to make the evaluation of this alternatives to select the most appropriate(s) in each case because factors as costs, systems or equipments availability, will define the applicability or not of a particular method.

QC 20120530

Made available in DSpace on 2016-06-02T20:00:37Z (GMT). No. of bitstreams: 1 3585.pdf: 4834479 bytes, checksum: 5a0924e0311d45a52820620dbafa4f6a (MD5) Previous issue date: 2011-03-23 / Universidade Federal de Minas Gerais / Most of Water Treatment Plant (WTP) for public supply in Brazil use surface water as source and conventional complete cycle as treatment system. In this type of treatment wastewater are restrained/generated which vary mainly according to the type and amount of chemical added and the characteristics of the water resource. This wastewater is found mainly in clarifiers (sludge) and backwash water filter (BWF) from WTP. Unfortunately, most of Brazilian WTP launches its waste directly into water resources, violating Brazilian Law 9605 published in 1998. There are mechanical and natural technologies for water removal from wastewater restrained during the treatment. Once known that wastewater from WTP has fluid characteristic, some technologies to remove its water have been developed. A natural one is the drainage bed, developed and proposed by Cordeiro (2001). The drainage bed has basically two stages: drainage and evaporation. This dissertation presents results of a study, whose centre objective was to achieve improvements in water sludge removal restrained in clarifiers by the use of plastic cover (evaporation stage). Results of effective tests in prototypes located in Sao Carlos WTP (Sao Paulo State) with plastic cover have showed that this roof (commercial reference PVC 0.30 milimeters) uses has accelerated the evaporation process, and has protected sludge from rain. The height of the roof that presented the best result was 0.20 meters in relation to the board of prototype, realizing to obtain a sludge 56% dryer than in tests without the roof. Preliminary tests in laboratory scale generated a promising scenario for the use of cationic polymer in large scale doubling the efficiency of the initial drainage of sludge. However, other laboratory tests with different characteristics of geotextile blanket only confirmed the superiority of using woven blanket type with surface density of 600 g/m² (which had already been used in other studies), compared to the others, in reference to obtain better efficiency at the initial drainage of water present in raw sludge. / A maior parte das Estações de Tratamento de Água (ETAs) para abastecimento existente no Brasil se utiliza de captação de águas superficiais e sistema de tratamento de ciclo completo convencional. Neste tratamento são retidos/gerados resíduos que variam principalmente segundo o tipo e quantidade de produto químico adicionado e as características do manancial de captação. Estes resíduos são encontrados principalmente nos decantadores (lodo) e na água de lavagem dos filtros (ALF) das ETAs. Infelizmente, a maioria das ETAs brasileiras lança seus resíduos diretamente em corpos d água, infringindo disposições da Lei 9.605/98. Existem tecnologias mecanizadas e naturais para remoção de água dos resíduos retidos no tratamento. Uma vez que possuem característica fluida, foram desenvolvidas algumas tecnologias para remoção de suas águas. Uma tecnologia natural para remoção de águas de resíduos de ETAs é o leito de drenagem, desenvolvido e proposto por Cordeiro (2001). O leito de drenagem possui basicamente duas etapas envolvidas: drenagem e evaporação. Esta pesquisa apresenta resultados de um estudo, cujo objetivo central foi alcançar melhorias na remoção da água de lodo retido nos decantadores através da utilização de cobertura plástica no leito de drenagem (etapa de evaporação). Resultados obtidos nesta pesquisa para ensaios realizados em protótipos de leitos de drenagem instalados na ETA de São Carlos-SP demonstraram que, quando se utiliza cobertura plástica (referência comercial PVC 0,30 mm), o processo de evaporação da água presente no lodo é acelerado e a ocorrência de precipitação não interfere em momento algum na remoção de água do lodo. A altura da cobertura em relação ao protótipo que apresentou os melhores resultados foi de 0,20 m, permitindo-se obter um lodo final até 56% mais seco que na ausência de cobertura. Ensaios realizados em escala laboratorial para condicionamento prévio do lodo bruto com polímero catiônico apresentaram resultados promissores para sua utilização em maior escala, duplicando a eficiência da drenagem inicial do lodo. Entretanto, outros ensaios laboratoriais com mantas geotêxteis de características distintas apenas confirmaram a superioridade da utilização de manta do tipo tecida de densidade superficial 600g/m² (que já havia sido utilizada em outras pesquisas) em relação às demais, no que se refere à obtenção de melhor eficiência na drenagem inicial da água presente no lodo bruto.

L'usage des lits de séchage plantés et non plantés (LSP et LSNP) pour le traitement des boues de vidange (BV) augmente en Afrique de l’Ouest malgré leurs performances parfois mauvaises et leur dimensionnement empirique. Pour contribuer à I'accès aux performances épuratoires des LSP et LSNP, le suivi de 13 lits de séchage expérimentaux a été réalisé. Sur la base de l'équation de consolidation de Terzaghi, un modèle, permettant de simuler I'humidité volumique des boues sur les lits, a été développé selon 2 approches. Les résultats montrent des performances épuratoires mitigées. Pour des valeurs seuils de concentrations de BV, les 3 espèces testées sur les LSP ont flétries. Les simulations avec l’Approche 1 présente des erreurs absolues relatives inférieures à 15% et sont meilleures que ceux avec l'approche 2. Cependant, I'approche 2 a l'avantage de reproduire les tendances de l'évolution des coefficients de consolidation et perméabilité des boues en fonction de la profondeur et du temps. / Despite the bad performances sometimes obtained according to the context and the empirical method of design, the use of drying beds (planted and not planted) for the treatment of faecal sludge (FS) increase in West Africa. To access to treatment performances in local context (Ouagadougou), the monitoring of 13 experimental drying beds were done. Based on the Terzaghi consolidation equation, the development of a numerical model were done according 2 approaches. Regarding removal efficiency, the performances of treatment of sludge on drying beds were mitigated. The results demonstrate that Oryza longistaminata, Sporobolus pyramidalis and Cyperus alopecuroïdes cannot be used in sludge drying planted beds for the treatment of FS. The simulations with the model in the approach 1 were better than those in approach 2. However, the approach 2 can reproduce the trends of volumetric moisture, the trends of consolidation coefficient and permeability as a function of depth and as a function of time.