Cette thèse propose un modèle dynamique d'un bioréacteur à membrane submergée (sMBR) comprenant les comportements physiques et biologiques du processus. La filtration (aspect physique) est un modèle de résistances en série composé de la résistance réversible (liée au processus de formation d'un gâteau qui peut être enlevé par lavage de l'air) et de la résistance à colmatage irréversible. La fonction biologique est mise en œuvre par l'extension du modèle de chemostat simple avec un mécanisme de filtration.L'analyse du modèle comprend : l'analyse asymptotique, l'observabilité, la contrôlabilité et l'étude dynamique lente et rapide. Cette dernière, basée sur le théorème de Tikhonov, révèle la possibilité de simplifier la dynamique du modèle en découplant le processus en trois échelles de temps : l'évolution du colmatage à long terme (dynamique lente), la dégradation biologique ( dynamique rapide) et la formation du gâteau (dynamique ultrarapide). Comme les processus avec sMBRs sont relativement nouveaux, les données réelles de processus sont difficiles à obtenir. Ainsi, une installation pilote d'un système de recirculation de l'aquaculture avec une sMBR est conçue, construite et automatisée. Des mesures en ligne du processus, tels que la température, les matières en suspension (MES), l'ammoniac et les concentrations des effluents nitrates, la croisée de l'air et des débits d'effluents et la pression transmembranaire, sont réunis afin de valider le modèle proposé.Pour mettre en évidence le cadre général du modèle proposé, le même modèle est composé d'ensembles de données réelles obtenues à partir d'une installation de traitement des eaux usées à sMBR. Par conséquent, une identification de paramètre est organisée en trois étapes correspondant aux trois échelles de temps obtenues à partir de l'analyse analytique. L'identification de paramètre est implémentée en utilisant une fonction de coût aux moindres carrés pondérés et l'inverse de la Fisher Matrix Information (FIM), qui est utilisé pour obtenir les intervalles de confiance des paramètres calculées par une borne inférieure sur la matrice de covariance des estimations des paramètres. La capacité du modèle à prédire la pression transmembranaire et la dégradation biologique est prouvée par la validation du modèle et la validation croisée des résultats.Concernant le contrôle du processus, deux approches différentes sont utilisées : un contrôleur partielle linéaire basé sur la théorie de Lyapunov est conçu afin de stabiliser la production encrassement en actionnant dans la croisée de l'air et les flux d'effluents; une commande prédictive de modèle non linéaire (NMPC) est mise en œuvre afin d'optimiser le taux de production d'effluent et de maximiser la période entre deux opérations de lessivage chimique.Les résultats présentés dans cette thèse montrent l'importance des études analytiques sur des modèles afin de traiter la cognition et la simplification de modèle. Un autre point important est la structure du modèle dynamique simple avec une petite quantité de paramètres. Ce travail montre que cette structure est suffisante pour mettre en œuvre des stratégies de contrôle avancé sur les processus sMBR et même de prédire la dégradation biologique et la dynamique de croissance du colmatage. / This thesis proposes a simple submerge membrane bioreactor (sMBR) dynamic model that comprises physical and biological process behaviors. The filtration, physical aspect, is a resistance-in-series model that is composed with reversible resistance, linked to sludge cake formation process that can be detached by air scouring, and the irreversible fouling resistance. The biological feature is implemented extending the simple chemostat model to the filtration mechanism. The model asymptotic analysis, observability, controllability and fast and slow dynamic study are carried out. The latter, based on the Tikhonov's theorem, reveals the possibility to simplify model dynamics by decoupling the process in three time scales, i.e. long-term fouling evolution (slow dynamic), biological degradation (fast dynamic) and fouling cake formation (ultrafast dynamic). As sMBR processes are relativity new, real process data are scarce. Thus, a recirculating aquaculture system pilot plant with an sMBR is design, build and automated. Process online measurements such as: temperature, total suspended solids (TSS), ammonia and nitrate effluent concentrations, air cross- and effluent flow rates and trans-membrane pressure are gathered in other to validate the proposed model. To evidence the model general framework the same model is confronted with real data sets obtained from an sMBR wastewater treatment plant. Therefore, a parameter identification is organized in three steps corresponding to the three time scales obtained from the analytical analysis. The parameter identification is implemented using a weighted least-squares cost function and the inverse of the Fisher Information Matrix (FIM), which is used to obtain the parameters confidence intervals, is computed by a lower bound on the covariance matrix of the parameter estimates. The model capacity to predict trans-membrane pressure and biological degradation is proved by model validation and cross-validation results, in which an accurate correlation coefficients (R^2) of approximately 0.83 are obtained. Concerning the process control, two different approach are used: a partial-linearizing feedback Lyapunov controller is designed in order to stabilize the fouling production by actuating in the air cross- and effluent flows; and a nonlinear model predictive control (NMPC) is implemented in other to optimize the effluent production rate and maximize the period between two chemical cleaning procedures. The results included in this thesis show the importance of analytical model studies in order to process cognition and model simplification. Another important point is the simple dynamic model structure, with a small quantity of the parameters, which is adequate to implement advanced control strategies on sMBR processes and, similarly, to predict biological degradation and fouling build-up dynamics.

The biological process known as activated sludge (AS) in conjunction with membrane separation technology for the treatment of wastewater has been employed for over four decades. While, membrane biological reactors (MBR) are now widely employed, the phenomenon of membrane fouling is still the most significant factor leading to performance decline of MBRs. Although much research has been done on the subject of MBR fouling over the past two decades, many questions remain unanswered, and consensus within the scientific community is rare. However, research has led to one system parameter generally being regarded as a contributor to membrane fouling, extracellular polymeric compounds (EPS). EPS, and more specifically, the soluble fraction of EPS known as soluble microbial products (SMP), must be further investigated in order to better understand membrane fouling. The biological activity and performance of the MBR is affected by myriad operational parameters, which in turn affects the SMP generated. A commonly varied operational parameter is, depending on the specific treatment needs of a MBR, the sludge retention time (SRT). This study aims to characterize the SMP in three bench-scale MBRs as the SRT is gradually lowered. By studying how the SMP change as the operation of the system is altered, greater understanding of how SMP are related to fouling can be achieved. At the onset of the study, a steady state was established in the system with a SRT of 20 days. Upon stabilization of a 20 day SRT, the system was gradually transitioned to a five and a half day SRT, in stepwise adjustments. Initially, both the trans-membrane pressure (TMP) and the SMP concentrations were at relatively low values, indicating the presence of minimal amounts of biofilm on the membrane surfaces. As the system was altered and more activated sludge was wasted from the reactors, the SRT inherently decreased. As the lower SRT was transitioned and established, the data from TMP measurements, as well as the results from SMP determination, confirmed the development of increased amounts of biofilm formed. An apparent relationship was observed between the operational condition of a lower SRT and the SMP found in the system.

Usually, image compression techniques that use only one transform exhibit some poor properties. For instance, the Discrete Cosine Transform (DCT) cannot efficiently represent high frequency components, resulting in blurred images. The Multiple Bases Representation (MBR) compression technique, which uses two or more transforms, is found to be superior to the single transform techniques in terms of representation efficiency. However, some bits in the MBR representation are needed to track the basis information. The MBR image quality is deteriorated by discontinuities at block boundaries, as is the standard DCT transform. In this thesis, test images are distorted by MBR compression using a Recursive Residual Projection algorithm. This algorithm is a sub-optimal method to find the best basis vector subset for representing images based on multiple orthogonal bases. The MBR distorted images are reconstructed by the iterative method of Projection onto Convex Sets (POCS). Many constraints that form convex sets are reviewed and examined. Due to the high distortion at the block boundaries, some constraints are introduced particularly to reduce artifacts at the boundaries. Some constraints add energy to the reconstructed images while others remove energy. Thus, the initial vectors play a key role in the performance of the POCS method for better MBR reconstruction. This thesis also determines the most appropriate initial vector for each constraint. Finally, the composite projections associated with the sign, minimum decreasing and norm-of-slope constraints are used to improve the reconstruction of the MBR distorted images and the effect of ordering of the projections is investigated. / Master of Science

MBR, Membrane BioReactor, is a relatively new wastewater treatment technique using membrane filtration to separate particles from the biologically treated water. By means of analyzing analysis results from KARV, the existing wastewater treatment plant in Kalmar, from the recent six years and assuming that PO4-P in the water from the secondary settling tank equalizes with total effluent phosphorus in an MBR, the opportunity of an MBR to reach future effluent requirements could be assessed. The future effluent requirement for phosphorus is expected to be 0.2 mg/L or 0.1 mg/L. Today the phosphorus effluent requirement in Kalmar is 0.3 mg/L total phosphorus as annual average. Results from data analysis presented in figures shows that with the same operation strategy as during the six evaluated years, the future requirements would not be reached. Phosphorus is essential for yield and performance of biomass in the biological treatment step. The starting position for the work is that the way of operation during the six recent years would have given exactly the right amount of P to the bacteria in the biological treatment step. An increased dose of chemicals for phosphorus removal could lead to P-deficiency in the biological treatment step and thus decreased efficiency. This effect could be an essential aspect in the design of a future MBR in Kalmar.

The performance of a submerged membrane bioreactor for the duty of gas field produced water treatment was appraised. The system was operated under steady state conditions at a range of mixed liquor suspended solids (MLSS) concentrations and treatment and membrane performance examined. Organics removal (COD and TOC) display removal rates between 90 and 97%. Removal of specific target compounds Benzene, Toulene, Ethylbenzene and Xylene were removed to above 99% in liquid phase with loss to atmosphere between 0.3 and 1%. Comparison of fouling rates at a number of imposed fluxes has been made between long term filtration trials and short term tests using the flux step method. Produced water fed biomass displays a greater fouling propensity than municipal wastewater fed biomass from previous studies. Results indicate an exponential relationship between fouling rate and flux for both long and short term trials, although the value was an order of magnitude lower during long term tests. Moreover, operation during long term trials is characterised by a period of pseudo stable operation followed by a catastrophic rise in TMP at a given critical filtration time (tfi, ) during trials at 6 g. L"1. This time of stable operation, tfit, is characterised by a linear relationship between fouling rate and flux. Results have been compared with the literature. Data for membrane fouling prior to the end of t fit yielded a poor fit with a recently proposed model. Trends recorded at t> trlt revealed the fouling rate to follow no definable trend with flux. The system showed resilience to free oil shocking up to an oil concentration of 200ppmv. Following an increase in oil concentration to 500 ppmv, rapid and exponential fouling ensued.

Made available in DSpace on 2014-06-11T19:29:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-19Bitstream added on 2014-06-13T19:38:24Z : No. of bitstreams: 1 bezerra_lf_me_ilha.pdf: 1874770 bytes, checksum: b6f02018abe581f4724626202c471af4 (MD5) / Universidade Estadual Paulista (UNESP) / As atividades industriais, principalmente as indústrias químicas e alimentícias que se utilizam dos processos fermentativos, geram efluentes com altas concentrações de matéria orgânica carbonácea e nitrogenada. Estas necessitam de sistemas complexos para o tratamento de suas águas residuárias, pois a emissão excessiva de nutrientes no corpo d’água pode resultar na ocorrência da eutrofização que interfere nos usos desejáveis do recurso hídrico e altera o equilíbrio ambiental. Neste sentido, o presente avaliou da remoção de matéria orgânica carbonácea e nitrogenada, bem como a determinação do fluxo crítico, em biorreator de membranas (MBR) tratando águas residuárias industriais do processo de produção de aminoácidos. Pelos resultados obtidos, constatou-se a viabilidade técnica no uso do MBR para ao tratamento dessas águas residuárias contendo 2505 mg DQO/L de material carbonáceo e 277 mg NTK/L de material nitrogenado. O biorreator foi operado com carga orgânica volumétrica de 1,91 ± 0,13 kg DQO/m³ dia e carga nitrogenada volumétrica de 0,18 ± 0,02 kg NTK/m³ dia, com recirculação interna de 4 vezes a vazão afluente. O efluente tratado apresentou concentrações médias de 59 ± 27 mg DQO/L, 0,60 ± 0,24 mg N-NH4 +/L e 20,5 ± 11,9 mg N-total/L, com eficiências médias de remoção de DQO, NTK e NT de 97,5%, 98,6% e 92,1%, respectivamente. O sistema de ultrafiltração foi testado em vários fluxos entre 25 e 37 LMH e determinou-se o fluxo crítico de 28 LMH para o sistema operando com 11,4 g/L de SST / Industrial activities, especially the chemical and food industries, that use fermentation processes, generate effluents with high concentrations of carbonaceous organic matter and nitrogen. These require complex systems to treat its wastewater, since the emission of excessive nutrients in the water body can result in the occurrence of eutrophication, which interferes with the desirable uses of water resource and changes the environmental balance. In this sense, this paper evaluated the carbonaceous organic matter and nitrogen removal as well as the determination of critical flux in membrane bioreactor (MBR) treating industrial wastewater from amino acids production. By the obtained results, it found the technical feasibility of MBR for the wastewater treatment containing 2505 mg COD / L of organic material and 277 mg TKN / L of nitrogen material. The bioreactor was operated with organic loading rate of 1.91 ± 0.13 kg COD / m³ day and nitrogen volumetric load of 0.18 ± 0,02 kg TKN / m day, with internal recirculation of 4 times. The treated effluent showed concentrations of 59 ± 27 mg COD / L, 0.60 ± 0.24 mg N-NH4 + / L and 20.5 ± 11.9 mg total N / L, with average removal efficiencies of COD , TKN and TN of 97.5%, 98.6% and 92.1%, respectively. The ultrafiltration system was tested at various flow rates between 25 and 37 LMH, to determine the critical flux of 28 LMH with the system operating at 11.4 g / L of TSS

Os produtos de cuidado pessoal (PCP) são substâncias utilizadas para fins de saúde, beleza e higiene, enquadrando-se como contaminantes de caráter emergente. Dentre os PCP estão os parabenos (alquil-p-hidroxibenzoatos), considerados desreguladores endócrinos, encontrados em águas fluviais e efluentes de estações de tratamento em concentrações na faixa de ng L-1 a ?g L-1. A presença destes compostos nessas matrizes reforça a importância de processos alternativos de tratamento de efluentes, como o processo de biorreator com membranas (MBR) e o processo oxidativo avançado (POA) baseado em persulfato (PS) ativado. Aliando um reator biológico e membranas de separação, o MBR destaca-se como alternativa para obtenção de efluentes de boa qualidade, com remoção de contaminantes por sorção, biodegradação e/ou retenção física. Em contrapartida, o POA com persulfato ativado utiliza radicais sulfato como espécie oxidante para degradação de poluentes. Este trabalho objetivou avaliar a remoção de metilparabeno (MeP) e propilparabeno (PrP) pelo processo MBR, bem como estudar a degradação de tais compostos por persulfato ativado com radiação UVA (UVA/PS) ou ferro de valência zero (Fe0/PS). Objetivou-se, outrossim, avaliar a remoção dos parabenos do permeado do MBR por esses POA. Os resultados mostraram que o processo MBR apresentou eficiência média de 95,9% na remoção de MeP e PrP ([parabenos]0 = 0,5 mg L-1) e eficiência média de 85% na remoção de PrP ([PrP]0 = 10 mg L-1). A degradação de MeP e PrP em mistura (50-500 ?g L-1, cada) por UVA/PS exibiu interferência de um parabeno sobre o outro. Assim, optou-se por investigar a degradação apenas de PrP (1 mg L-1) via UVA/PS e Fe0/PS. Para UVA/PS (120 min), quanto maior a irradiância e a concentração inicial de PS, menor o tempo de meia-vida, sendo possível atingir t1/2 mínimo de 37,9 min, com remoção máxima de 77,3%. Para Fe0/PS (15 min), obteve-se um mínimo de t1/2 igual a 0,65 min, para [PS]0 = 5,38 mmol L-1 e [Fe0]0 = 51,6 mg L-1, com porcentagens de degradação superiores a 97% para todos os ensaios realizados. Nesses casos, a identificação de intermediários de degradação do PrP para os processos UVA/PS e Fe0/PS permitiu comprovar a formação de benzoato de propila, benzoato de metila, ácido 4-hidroxibenzoico e MeP. Finalmente, no tratamento do permeado do MBR, obtiveram-se remoções de PrP de 24,5% para UVA/PS (120 min) e de 61,2% para Fe0/PS (90 min), o que se deve ao efeito da matriz complexa. / Personal care products (PCP) are substances used for health, beauty and hygiene purposes, and are classified as emerging contaminants. Parabens (alkyl-p-hydroxybenzoates), included among the PCPs, are considered endocrine disrupters and found in river waters and effluents from wastewater treatment plants, at concentrations ranging from ng L-1 to ?g L-1. The presence of these compounds in environmental matrices reinforces the importance of alternative effluent treatments, such as membrane bioreactors (MBR) and advanced oxidation processes (AOP) based on activated persulfate (PS). The MBR combines a biological reactor and membrane separation membranes, standing out as an alternative to obtain good quality effluents, with contaminants removed by sorption, biodegradation and/or physical retention. In contrast, the AOP based on activated persulfate uses sulfate radicals as oxidizing species for the degradation of pollutants. This work aimed to evaluate the removal of methylparaben (MeP) and propylparaben (PrP) by the MBR process, as well as to investigate the degradation of these compounds by using persulfate activated with UVA radiation (UVA/PS) or zero valence iron (Fe0/PS). The results showed that the MBR process achieved 95.9% MeP and PrP removals ([parabens]0 = 0.5 mg L-1), and 85% PrP removal ([PrP]0 = 10 mg L-1). However, the degradation of MeP and PrP in the mixture (50-500 ?g L-1, each) by the UVA/PS process exhibited the interference of one paraben over the other. It was therefore decided to investigate the degradation of only PrP (1 mg L-1) via UVA/PS and Fe0/PS. For the UVA/PS process (120 min), the higher the irradiance and the initial PS concentration, the shorter the PrP half-life time, with a minimum t1/2 of 37.9 min and maximum removal of 77.3%. For Fe0/PS (15 min), a minimum t1/2 equal to 0.65 min was achieved for [PS]0 = 5.38 mmol L-1 and [Fe0]0 = 51.6 mg L-1, with percent removals higher than 97% for all the experiments performed. In these cases, the identification of PrP degradation intermediates for the UVA/PS and Fe0/PS processes allowed to prove the formation of propyl benzoate, methyl benzoate, 4-hydroxybenzoic acid, and MeP. Finally, regarding the post-treatment of the MBR permeate, lower PrP removals of 24.5% for the UVA/PS process (120 min), and 61.2% for Fe0/PS (90 min) were obtained, which are due to the effect of the complex aqueous matrix.

Vid Hammarby Sjöstadsverk drivs en pilotanläggning som är en mindre skala av det framtida avloppsreningsverket i Henriksdal. Delar av reningsprocessen består av membranbioreaktorer. I pilotanläggningen finns en zon kallad RAS-DeOx dit returslammet från membrantankarna och rejektvattnet från slambehandlingen leds. Luftning av membrantankarna gör att returslammet är syrerikt och rejektvattnet innehåller mycket ammonium.Zonen fungerar som ett nitrifikationssteg då syret i returslammet kan oxidera ammoniumet från rejektvattnet. Dessutom kan zonen minska syrehalterna i returslammet för att undvika att det hamnar i pilotanläggningens fördenitrifikation. För att få bättre uppfattning om vad som sker i zonen och hur denna fungerar som ett nitrifikationssteg studerades nitrifikation, denitrifikation och syreförbrukningen i zonen. För att utvärdera RAS-DeOx-zonen belastades den med olika nivåer av ammonium från rejektvattnet vid olika hög luftning i membrantankarna. Detta utfördes både experimentellt direkt på pilotanläggningen och i en simuleringsstudie där processimuleringar genomfördes i en simuleringsmodell. I modellen utvärderades även två styrstrategier för zonen.Resultaten från studierna visade att både nitrifikation och denitrifikation förekom i zonen. Jämfört med simuleringsstudien varierade omfattningen av nitrifikation och denitrifikation mer i den experimentella studien. Båda studierna visade att det fanns risk att syre hamnande i pilotanläggningens fördenitrifikation. Styrstrategierna visade att det inte var fördelaktigt för pilotanläggningens resurseffektivitet att zonen luftades vid hög ammoniumbelastning från rejektvattnet. Det visade sig också att det var ingen större skillnad när det gällde pilotanläggningens prestation vid högt, lågt eller styrt returflöde för zonen. Däremot skiljde sig prestationen mer avseende luftning och koldosering.Utöver att det förekom nitrifikation och denitrifikation i zonen bedömdes den även fungera som ett nitrifikationssteg för ammoniumet i rejektvattnet. Dessutom minskade den syrehalterna i returslammet. Hur väl ammonium nitrifierades och syre förbrukades i zonen berodde på förhållandena i pilotanläggningen och förhållandet mellan mängden ammonium och syre i zonen. / At Hammarby Sjöstadsverk there is a pilot plant which is a smaller version of the future wastewater treatment plant at Henriksdal. Parts of the treatment process steps are membrane bioreactors. There is a zone in the pilot plant which is called RAS-DeOx to where the return activated sludge from the membrane tanks and the reject water from the sludge treatment are pumped. The return activated sludge contains oxygen since the membranetanks are aerated and the reject water has high contents of ammonium.The zone works as a nitrification step for the ammonium in the reject water, and also reduces the oxygen levels in the return sludge to avoid oxygen in the pilot plant's pre-denitrification step. To aquire a better understanding of what occurs in the zone and how it functions as a nitrification step; nitrification, denitrification and oxygen consumption was studied in the zone. To evaluate the RAS-DeOx-zone it was loaded with different loads of ammonium from the reject water at different levels of aeration in the membrane tanks. This was evaluated both experimentally at the pilot and in a simulation model of the pilot. In the simulation model two control strategies for the zone were also evaluated.It was shown that both nitrification and denitrification occurred in the zone. Furthermore, both studies showed that there is a risk that oxygen occurs in pilot's pre-denitrification step if the ammonium load in zone was low. Then, all of oxygen in the zone was not consumed. As for the control strategies, it was shown that the benefits were low for the resource efficiency of the pilot when the zone was aerated during high loads of ammonium. The performance of the pilot was similiar for high, low and regulated return flows for the zone, but the aeration and carbon dosage in the pilot differed.Besides that both nitrification and denitrification occurred in the zone, it was also functioning as a nitrification step for the ammonium from the reject water. The oxygen from the return sludge was reduced as well. The extent of nitrification and consumption of oxygen in the zone depended on the circumstances in the pilot and the relationship between the amount of oxygen and ammonium.

För att kunna möta framtidens striktare reningskrav för avloppsvatten och en ökad belastning på grund av befolkningstillväxt bygger Stockholm Vatten och Avfall (SVOA) om Henriksdals reningsverk inom projektet Stockholms Framtida Avloppsvattenrening (SFA). En av de större förändringarna i det framtida Henriksdals reningsverk är införandet av MBR-teknik, där slam och vatten avskiljs genom membranfiltrering. Separationen medför förändrade egenskaper hos slammet då en större andel av partiklarna kan avskiljas från utgående vatten jämfört med avskiljning från konventionella sedimentationsbassänger. På Hammarby Sjöstadsverk drivs en pilotanläggning där MBR-teknik undersöks inför implementering i framtida Henriksdals reningsverk. Denna studie har undersökt skillnader i mängd partiklar, organiskt innehåll, filtrerbarhet, sedimenteringsegenskaper och förtjockningskapacitet hos överskottslam från MBR-linjen på Hammarby Sjöstadsverk (ÖS-MBR) och Henriksdals reningsverk (ÖS-CAS). Detta för att ge underlag till optimering av framtida slambehandling på Henriksdals reningsverk. Därutöver har massbalans för förtjockningsförsöken beräknats. Resultatet av studien visar att egenskaperna hos ÖS-MBR och ÖS-CAS skiljer sig tydligt för torrsubstans (TS), totalt suspenderade partiklar (TSS) och filtrerbarhet (TTF). Ingen skillnad i slamvolymindex (SVI) kunde verifieras i studien. Efter förtjockning av slammen i en trumsil, med olika polymertillsats, uppvisade ÖS-MBR högre TSS i rejektvattnet än ÖS-CAS. Denna skillnad indikerar att partiklar i ÖS-MBR har mindre benägenhet att binda till polymeren som användes, än partiklar i ÖS-CAS. Det är därför av betydelse att pröva ut rätt typ av polymer vid förtjockning av ÖS-MBR, för att nå målet på en TSS under 1000 mg/L i rejektvattnet. Därtill uppvisade ÖS-MBR högre TS i det förtjockade slammet än ÖS-CAS. Detta skulle kunna indikera att ÖS-MBR är lättare att förtjocka än ÖSCAS, men det kunde dock inte bekräftas av massbalanserna. Slutligen kunde denna studie inte samstämmigt visa på en skillnad i potentialen att förtjocka de båda slammen då fördelningen av partiklar mellan förtjockat slam och rejektvatten varierade i varje försök. Däremot minskade TSS i rejektvattnet med högre dos av polymer medan samma samband inte gällde för TS i det förtjockade slammet där dosen polymer, efter en viss mängd, hade en begränsad påverkan på TS. En viktig aspekt som påverkade förtjockningskapaciteten i denna studie var igensättning av trumsilen. Centrifuger, som kommer att användas i framtida Henriksdals reningsverk, kommer inte uppvisa samma typ av störningar i driften. / To comply with future stricter regulations on treated wastewater and an increasing load on the system due to a growing population, the Stockholm Vatten och Avfall Company (SVOA) is upgrading the Henriksdal wastewater treatment plant within the project Stockholm’s Future Wastewater Treatment (SFA). One of the main changes in the future plant is the introduction of MBR-treatment, where sludge and water will be separated through the use of membranes. This separation will change the composition of the sludge by removing a larger fraction of particles from the effluent than what can be achieved in conventional sedimentation basins. Hammarby Sjöstadsverk operates a pilot plant with a MBR-process, where the technology is evaluated before the implementation in the future Henriksdal wastewater treatment plant. This study examines the difference in the sludge characteristics, i.e. sedimentation, filterability, and the potential for thickening of excess sludge from the MBR-process in Hammarby Sjöstadsverk (ÖS-MBR) and from the activated sludge process in the current Henriksdal wastewater treatment plant (ÖS-CAS). Furthermore, a mass balance and a sensitivity analysis has been used within this study. The study aimed at providing decision support for optimisation of the sludge treatment at the future Henriksdal wastewater treatment plant once the MBR process is implemented. The results of this study show that the characteristics of ÖS-MBR and ÖS-CAS differ considerably in total solids (TS), total suspended solids (TSS) and filterability (TTF). No difference in sludge volume index (SVI) could be verified between the two types of sludges. After thickening in a rotary drum screen with different doses of polymer, the TSS in the reject water was higher for the ÖS-MBR than the ÖS-CAS. This difference indicates that particles in ÖS-MBR are less attracted to the particular thickening polymer used, than the particles in ÖS-CAS. Therefore, it is important to select the correct type of polymer when thickening ÖS-MBR in order to reach the target TSS of 1000 mg/L in the reject water. In addition, the thickened ÖS-MBR showed higher TS than ÖS-CAS. This could indicate that ÖS-MBR would be easier to thicken; however, this is not confirmed by the mass balances. In the end, this study could not conclusively show any trend in the level of thickening between the two types of sludges because the distribution of particles varied in each trial. Nevertheless, while a higher dosage of polymer evidently reduced the TSS in the reject water, the same was not true for the TS in the thickened sludge, which seems to be less affected by the dose of polymer after a certain level. An important consideration in this study was the clogging of the drum screen. However, centrifuges, which will be used in the future Henriksdal wastewater treatment plant, do not have the same operational problems.

The work presented in this thesis leads to the formulation of a dynamic mathematical model of an immersed membrane bioreactor (iMBR) for wastewater treatment. This thesis is organised into three parts, each one describing a different set of tasks associated with model development and simulation. In the first part, the Author qualitatively and quantitatively compares various published activated sludge models, i.e. models of biochemical processes associated with bacterial growth, decay, lysis and substrate utilisation in activated sludge systems. As the thesis is focused on modelling membrane bioreactors (MBRs) which are known to experience membrane fouling as a result of adsorption of biopolymers present in the bulk liquid onto and within the membrane, all activated sludge models considered in this thesis are able to predict, with various levels of accuracy, the concentrations of biopolymeric substances, namely soluble microbial products (SMP) and extracellular polymeric substances (EPS). Some of the published activated sludge models dedicated to modelling SMP and EPS kinetics in MBR systems were unable to predict the SMP and EPS concentrations with adequate levels of accuracy, without compromising the predictions of other sludge and wastewater constituents. In other cases, the model equations and the assumptions made by their authors were questionable. Hence, two new activated sludge models with SMP and EPS as additional components have been formulated, described, and simulated. The first model is based on the Activated Sludge Model No. 1 (ASM1) whereas the second model is based on the Activated Sludge Model No. 3 (ASM3). Both models are calibrated on two sets of data obtained from a laboratory-scale system and a full-scale system and prove to be in very good agreement with the measurements. The second part of this thesis explains the development of two membrane fouling models. These models are set to describe the loss of membrane permeability during filtration of various solutions and suspensions. The main emphasis is placed on filtration of activated sludge mixtures, however the models are designed to be as general as feasibly possible. As fouling is found to be caused by a large number of often very complex processes which occur at different spatial as well as temporal scales, the two fouling models developed here have to consider a number of significant simplifications and assumptions. These simplifications are required to balance the model's accuracy, generality and completeness with its usability in terms of execution times, identifiability of parameters and ease of implementation in general purpose simulators. These requirements are necessary to ascertain that long term simulations as well as optimisation and sensitivity studies performed in this thesis either individually on fouling models or on the complete model of a MBR can be carried out within realistic time-scales. The first fouling model is based on an idea that fouling can be subdivided into just two processes: short-term reversible fouling and long-term irreversible fouling. These two processes are described with two first order ordinary differential equations (ODEs). Whilst the first model characterises the membrane filtration process from an observer's input-output point of view without any rigorous deterministic description of the underlying mechanisms of membrane fouling, the second model provides a more theoretical and in-depth description of membrane fouling by incorporating and combining three classical macroscopic mechanistic fouling equations within a single simulation framework. Both models are calibrated on a number of experimental data and show good levels of accuracy for their designated applications and within the intended ranges of operating conditions. In the third part, the first developed biological model (CES-ASM1) is combined with the behavioural fouling model and the links between these two models are formulated to allow complete simulation of a hollow fibre (HF) immersed membrane bioreactor (iMBR). It is assumed that biological processes affect the membrane through production of mixed liquor suspended solids (MLSS), SMP and EPS which cause pore blockage, cake formation, pore diameter constriction, and affect the specific cake resistance (SCR). The membrane, on the other hand, has a direct effect on the bulk liquid SMP concentration due to its SMP rejection properties. SMP are assumed to be solely responsible for irreversible fouling, MLSS is directly linked to the amount of cake depositing on the membrane surface, whereas EPS content in activated sludge affects the cake's SCR. Other links provided in the integrated MBR model include the effects of air scouring on the rate of particle back-transport from the membrane surface and the effects of MLSS concentration on oxygen mass transfer. Although backwashing is not described in great detail, its effects are represented in the model by resetting the initial condition in the cake deposition equation after each backwash period. The MBR model was implemented in Simulink® using the plant layout adopted in the MBR benchmark model of Maere et al. [160]. The model was then simulated with the inputs and operational parameters defined in [36, 160]. The results were compared against the MBR benchmark model of Maere et al. [160] which, contrary to this work, does not take into account the production of biopolymers, the membrane fouling, nor any interactions between the biological and the membrane parts of an MBR system.