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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Kinetics of Anionic Surfactant Anoxic Degradation

Camacho, Julianna G. 2010 May 1900 (has links)
The biodegradation kinetics of Geropon TC-42 (trademark) by an acclimated culture was investigated in anoxic batch reactors to determine biokinetic coefficients to be implemented in two biofilm mathematical models. Geropon TC-42 (trademark) is the surfactant commonly used in space habitation. The two biofilm models differ in that one assumes a constant biofilm density and the other allows biofilm density changes based on space occupancy theory. Extant kinetic analysis of a mixed microbial culture using Geropon TC-42 (trademark) as sole carbon source was used to determine cell yield, specific growth rate, and the half-saturation constant for S0/X0 ratios of 4, 12.5, and 34.5. To estimate cell yield, linear regression analysis was performed on data obtained from three sets of simultaneous batch experiments for three S0/X0 ratios. The regressions showed non-zero intercepts, suggesting that cell multiplication is not possible at low substrate concentrations. Non-linear least-squares analysis of the integrated equation was used to estimate the specific growth rate and the half-saturation constant. Net specific growth rate dependence on substrate concentration indicates a self-inhibitory effect of Geropon TC-42 (trademark). The flow rate and the ratio of the concentrations of surfactant to nitrate were the factors that most affected the simulations. Higher flow rates resulted in a shorter hydraulic retention time, shorter startup periods, and faster approach to a steady-state biofilm. At steady-state, higher flow resulted in lower surfactant removal. Higher influent surfactant/nitrate concentration ratios caused a longer startup period, supported more surfactant utilization, and biofilm growth. Both models correlate to the empirical data. A model assuming constant biofilm density is computationally simpler and easier to implement. Therefore, a suitable anoxic packed bed reactor for the removal of the surfactant Geropon TC-42 (trademark) can be designed by using the estimated kinetic values and a model assuming constant biofilm density.
2

Kinetics of Anionic Surfactant Anoxic Degradation

Camacho, Julianna G. 2010 May 1900 (has links)
The biodegradation kinetics of Geropon TC-42 (trademark) by an acclimated culture was investigated in anoxic batch reactors to determine biokinetic coefficients to be implemented in two biofilm mathematical models. Geropon TC-42 (trademark) is the surfactant commonly used in space habitation. The two biofilm models differ in that one assumes a constant biofilm density and the other allows biofilm density changes based on space occupancy theory. Extant kinetic analysis of a mixed microbial culture using Geropon TC-42 (trademark) as sole carbon source was used to determine cell yield, specific growth rate, and the half-saturation constant for S0/X0 ratios of 4, 12.5, and 34.5. To estimate cell yield, linear regression analysis was performed on data obtained from three sets of simultaneous batch experiments for three S0/X0 ratios. The regressions showed non-zero intercepts, suggesting that cell multiplication is not possible at low substrate concentrations. Non-linear least-squares analysis of the integrated equation was used to estimate the specific growth rate and the half-saturation constant. Net specific growth rate dependence on substrate concentration indicates a self-inhibitory effect of Geropon TC-42 (trademark). The flow rate and the ratio of the concentrations of surfactant to nitrate were the factors that most affected the simulations. Higher flow rates resulted in a shorter hydraulic retention time, shorter startup periods, and faster approach to a steady-state biofilm. At steady-state, higher flow resulted in lower surfactant removal. Higher influent surfactant/nitrate concentration ratios caused a longer startup period, supported more surfactant utilization, and biofilm growth. Both models correlate to the empirical data. A model assuming constant biofilm density is computationally simpler and easier to implement. Therefore, a suitable anoxic packed bed reactor for the removal of the surfactant Geropon TC-42 (trademark) can be designed by using the estimated kinetic values and a model assuming constant biofilm density.
3

Groundwater nitrate reduction in a simulated free water surface wetland system

Misiti, Teresa Marie 17 November 2009 (has links)
Wetland-based treatment systems are often implemented as a method to remove unwanted substances from contaminated groundwater. Wetlands are effective due to the high biological activity that naturally takes place in the rhizosphere and soil. In support of a demonstration surface wetland system at a site in Columbus, Georgia, laboratory-scale wetland systems were designed to study the effect of different carbon sources and their biodegradability, COD:N ratio and temperature on the rate and extent of nitrate reduction of nitrate-bearing groundwater. Nitrate reducing bacteria are ubiquitous in surface and subsurface wetlands but a major limiting factor for these systems is carbon availability. Two major carbon sources were investigated in both continuous-flow and batch systems: a natural source, hay and a commercial source, MicroC GTM, a concentrated carbohydrate mix. Between these two carbon sources, the nitrate removal rate was not significantly different as long as sufficient biodegradable carbon was provided. The effect of both hydraulic retention time (HRT) and COD:N ratio on nitrate removal were investigated in continuous-flow systems. The specific nitrate removal rate in open to the atmosphere batch reactors was estimated at 0.55 mg N/mg biomass VSS-day. The effluent nitrate concentration in a continuous-flow system maintained with an HRT of 5 days at room temperature (22 to 23°C) was less than 3 mg nitrate-N/L. The COD:N ratio was kept at 6:1 for the majority of the experiments (approximately twice the theoretical requirement) to ensure sufficient carbon loading. Lower COD:N ratios of 5, 4, 3, 2, 1, and 0.5 were also investigated in the continuous-flow system and the minimum required carbon loading to achieve an effluent nitrate concentration below 10 mg N/L for an influent groundwater nitrate concentration between 65 and 70 mg N/L was determined to be 5:1 COD:N. The effect of temperature on the nitrate removal rate was also investigated at 22, 15, 10 and 5°C. As expected, the rate of nitrate reduction decreased with the decrease in temperature, especially below 10°C. Overall, the surface wetland is a feasible solution to treating nitrate-bearing groundwater even at relatively low ambient temperature values, provided that sufficient, biodegradable carbon is present.
4

A STELLA Model for Integrated Algal Biofuel Production and Wastewater Treatment

Cormier, Ivy 18 October 2010 (has links)
Based on a municipal wastewater treatment plant (WWTP) in Tampa, FL, a dynamic multiple-systems model was developed on the STELLA software platform to explore algae biomass production in wastewater by incorporating two photobioreactors into the WWTP‟s treatment train. Using a mass balance approach, the model examined the synergy through algal growth and substrate removal kinetics, as well as macroeconomic-level analyses of algal biomass conversion to biodiesel, biogas, or fertilizer. A sensitivity analysis showed that biomass production is highly dependent on Monod variables and harvesting regime, and profitability was sensitive to processing costs, market prices of products, and energy environment. The model demonstrated that adequate nutrients and carbon dioxide are available in the plant‟s influent to sustain algal growth. Biogas and fertilizer production were found to be profitable, but biodiesel was not, due to high processing costs under current technologies. Useful in determining the growth potential on a macro-level, the model is a tool for identifying focus areas for bench and pilot scale testing.
5

Luftflödesstyrning på Käppalaverket – utvärdering av konstanta styrsignaler / Aeration control at the Käppala wastewater treatment plant - evaluation of constant control signals

Nordenborg, Åsa January 2011 (has links)
På Käppalaverket i Stockholm står luftningen av de biologiska bassängerna för omkring en femtedel av verkets totala elenergiförbrukning. I ett försök att minska energikostnaden utvärderades under hösten 2010 nya metoder för luftflödesreglering på verket. Grundtanken var att styra luftflödet efter medelvärdet på utgående ammoniumkoncentration under en längre tid, istället för som idag efter momentana värden. Ett vanligt sätt att styra luftflöden på reningsverk idag är att använda återkoppling från utgående ammoniumkoncentration, vilket syftar till att alltid hålla den utgående koncentrationen vid ett valt börvärde. Lagstiftade gränsvärden på ammonium avser dock normalt medelvärden över en längre tid, såsom kvartal eller år. Istället för att anpassa luftflödet efter den inkommande belastningen är det därför möjligt att hålla luftflödet relativt konstant medan istället den utgående koncentrationen tillåts variera. I denna studie visades en energibesparing kunna erhållas om luftflödets variation reduceras. Två strategier utvärderades i vilka luftflödet respektive syrehalten hölls så konstant som möjligt. Dessa jämfördes med den idag använda styrstrategin på Käppalaverket, i vilken luftflödet anpassas efter den inkommande belastningen genom återkoppling. Studien inkluderade både simuleringar i modellen Benchmark Simulation Model no. 1 och fullskaleförsök på Käppalaverket. I både simuleringar och fullskaleförsök resulterade de två utvärderade strategierna i en lägre luftförbrukning per reningsgrad än den idag använda återkopplingsstrategin. I fullskaleförsöken erhölls en luftflödesreduktion på 11 % då luftflödet hölls konstant och 15 % då syrehalten hölls konstant. Båda strategierna genererade dock en kraftigt varierande utgående ammoniumkoncentration. Variationerna var störst då luftflödet hölls konstant och korrelerade inte med den dygnsbaserade belastningsprofilen. Sammanfattningsvis visade studien att en reducering av luftflödets variation resulterar i en lägre luftförbrukning men också i en ökad instabilitet. En konstant syrehalt gav en större energivinst och även en stabilare ammoniumreduktion än ett konstant luftflöde, varför denna metod har störst potential till vidare implementering i fullskala. / The aeration of the bioreactors is responsible for one fifth of the energy consumption at the Käppala wastewater treatment plant (WWTP) in Stockholm. In this report, new methods for aeration control were evaluated in order to reduce the energy costs at the plant. The main idea was to control the effluent ammonia concentration in terms of mean values instead of momentary values. A quite common approach for aeration control is to use feedback from the effluent ammonia concentration, thus aiming to keep the effluent concentration consistently at a certain set point. However, discharge limits normally refer to mean values over longer periods of time, such as months or years. Instead of adjusting the airflow to the incoming load it is therefore possible the keep the airflow fairly constant while allowing a fluctuating effluent concentration. In this paper, it was shown that by reducing the variation of the airflow, energy could be saved. Two methods were evaluated in which the airflow and oxygen concentration respectively was held constant. These methods were compared to the control strategy used today at the Käppala WWTP, where feedback control adjusts the airflow to the influent load. The study consisted of simulations with the Benchmark simulation model no. 1 (BSM1) as well as full scale experiments at the Käppala WWTP. Both the simulations and full scale experiments showed a reduced aeration per nutrient removal for the evaluated methods. In full scale, the total airflow reduction was 11 % when the airflow was held constant and 15 % when the oxygen concentration was held constant. However, the methods resulted in large variations of the effluent ammonia concentration, which did not correlate to the daily influent load. The variations were especially large when the airflow was held constant. In summary, this study showed that a reduced airflow variation results in lower aeration costs but also less stability. A constant oxygen concentration required less aeration and provided a more stable degree of ammonia removal than a constant airflow. For this reason, aeration control with a constant oxygen concentration has the best potential for further use at the Käppala WWTP.
6

Optimal steady-state design of bioreactors in series with Monod growth kinetics / Optimal design av bioreaktorer i serie vid steady-state med tillväxt som följer Monodkinetik

Hanna, Molin January 2018 (has links)
Bioreactors are used to carry out bioprocesses and are commonly used in e.g. biogas production and wastewater treatment. Two common hydraulic models of bioreactors are the continuous stirred tank reactor (CSTR) and the plug-flow reactor (PFR). In this paper, a differential equation system that describes the substrate, biomass and inert biomass in the bioreactors is presented. It is used in a steady-state analysis and design of CSTRs in series. Monod kinetics were used to describe the specific growth rate and the decay of biomass was included. Using the derived systems of differential equations, two optimization problems were formulated and solved for both CSTRs in series and for a CSTR+PFR. The first optimization problem was to minimize the effluent substrate level given a total volume, and the second was to minimize the total volume needed to obtain a certain substrate conversion. Results show that the system of differential equations presented can be used to find optimal volume distributions that solves the optimization problems. The optimal volume for N CSTRs in series decreases as N increases, converging towards a configuration of a CSTR followed by a PFR. Analyzing how the decay rate affects the results showed that when the total volume was kept constant, increasing the decay rate caused less difference between the configurations. When the total volume was minimized, increasing the decay rate caused the configurations to diverge from each other. The presented model can be used to optimally divide reactors into smaller zones and thereby increasing the substrate conversion, something that could be of interest in e.g. existing wastewater treatment plants with restricted space. A fairly accurate approximation to the optimal design of N CSTRs in series is to use the optimal volume for the CSTR in the configuration with a CSTR+PFR and equally distribute the remaining volumes. / Bioreaktorer används för att utföra olika biologiska processer och används vanligen inom biogasproduktion eller för rening av avloppsvatten. Två vanliga hydrauliska modeller som används vid modellering av bioreaktorer är helomblandad bioreaktor (på engelska continuous stirred tank reactor, CSTR) eller pluggflödesreaktor (på engelska plug-flow reactor, PFR). I den här rapporten presenteras ett system av differentialekvationer som används för att beskriva koncentrationerna av substrat, biomassa och inert biomassa i både CSTR och PFR. Ekvationssystemet används för analys och design av en serie CSTRs vid steady-state. Tillväxten av biomassa beskrivs av Monod-kinetik. Avdödning av biomassa är inkluderat i studien. Från ekvationssystemet formulerades två optimeringsproblem som löstes för N CSTRs i serie och för CSTR+PFR. Det första optimerinsproblemet var att minimera substrathalten i utflödet givet en total volym. I det andra minimerades den totala volymen som krävs för att nå en viss substrathalt i utflödet. Resultaten visade att ekvationssystemet kan användas för att hitta den optimala volymsfördelningen som löser optimeringsproblemen. Den optimala volymen för N CSTRs i serie minskade när antalet CSTRs ökade. När N ökade konvergerade resultaten mot de för en CSTR sammankopplad med en PFR. En analys av hur avdödningshastigheten påverkade resultaten visade att en ökad avdödningshastighet gav mindre skillnad mellan de två olika konfigurationerna när den totala volymen hölls konstant. När den totala volymen istället minimerades ledde en ökad avdödningshastighet till att de två konfigurationerna divergerade från varandra. Modellen som presenteras i studien kan användas för att fördela en total reaktorvolym i mindre zoner på ett optimalt sätt och på så vis öka substratomvandlingen, något som kan vara av intresse i exempelvis befintliga avloppsreningsverk där utrymmet är begränsat. En relativt bra approximation till den optimala designen av N CSTRs i serie är att optimera volymerna för en CSTR+PFR, använda volymen för CSTR som första volym i konfigurationen med N CSTR i serie, och sedan fördela den kvarvarande volymen lika mellan de övriga zonerna.
7

Effect of nutrient momentum and mass transport on membrane gradostat reactor efficiency

Godongwana, Buntu January 2016 (has links)
Thesis submitted in fulfilment of the requirements for the degree Doctor technologiae (engineering: chemical) In the faculty of engineering at the cape peninsula university of technology / Since the first uses of hollow-fiber membrane bioreactors (MBR’s) to immobilize whole cells were reported in the early 1970’s, this technology has been used in as wide ranging applications as enzyme production to bone tissue engineering. The potential of these devices in industrial applications is often diminished by the large diffusional resistances of the membranes. Currently, there are no analytical studies on the performance of the MBR which account for both convective and diffusive transport. The purpose of this study was to quantify the efficiency of a biocatalytic membrane reactor used for the production of enzymes. This was done by developing exact solutions of the concentration and velocity profiles in the different regions of the membrane bioreactor (MBR). The emphasis of this study was on the influence of radial convective flows, which have generally been neglected in previous analytical studies. The efficiency of the MBR was measured by means of the effectiveness factor. An analytical model for substrate concentration profiles in the lumen of the MBR was developed. The model was based on the solution of the Navier-Stokes equations and Darcy’s law for velocity profiles, and the convective-diffusion equation for the solute concentration profiles. The model allowed for the evaluation of the influence of both hydrodynamic and mass transfer operating parameters on the performance of the MBR. These parameters include the fraction retentate, the transmembrane pressure, the membrane hydraulic permeability, the Reynolds number, the axial and radial Peclet numbers, and the dimensions of the MBR. The significant findings on the hydrodynamic studies were on the influence of the fraction retentate. In the dead-end mode it was found that there was increased radial convective flow, and hence more solute contact with the enzymes/biofilm immobilised on the surface of the membrane. The improved solute-biofilm contact however was only limited to the entrance half of the MBR. In the closed shell mode there was uniform distribution of solute, however, radial convective flows were significantly reduced. The developed model therefore allowed for the evaluation of an optimum fraction retentate value, where both the distribution of solutes and radial convective flows could be maximised.
8

ANAEROBIC DIGESTION OF MICROALGAE: MODELING AND IDENTIFICATION FOR OPTIMIZATION AND CONTROL

Cameron, Elliot T. 04 1900 (has links)
<p>Owing to the rise in fossil fuel prices, overall energy security concerns, and the current push towards green engineering; renewable and green fuels have seen an increase in interest in recent years. Two notable technologies in this green movement are the production of biodiesel from microalgae and the production of biogas from anaerobic digestion of waste biomass. Production of biodiesel from microalgae was studied extensively in the 80s through the early 90s and found to be economically infeasible given the technology of the time. However, recent literature has suggested that one possible method to improve the feasability of the process would be to combine it with an anaerobic digestor to provide nutrient and biomass recycling. For such a system, having accurate models of each process would be highly advantageous for optimal design and control. To this end this thesis moves towards this overall goal by examining and modelling the anaerobic digestion of the microalgae <em>Chlorella vulgaris</em>.</p> <p>Starting with a set of experimental data (anaerobic digestion of <em>Chlorella vulgaris</em>) provided by LBE-INRA, the minimum number of kinetic equations needed to predict the data are found using principal component style analysis. This number is found to be two to three reactions. Using this as a basis for model development, a mass balance model is developed around both two and three reaction cases. To date there is very little literature on the modelling of anaerobic digestion of microalgae and so kinetic laws are selected from the general anaerobic digestion models ``Anaerobic Digestor Model 1'' (ADM1) and ``Acidogenesis/Methanogenisis Model'' (AM2). Given that the kinetic laws were derived from general literature, model fitting is a must. To faciliate this process a novel systematic parameter identification procedure to locate identifiable parameter subsets within each model is presented. Applying this novel procedure to the provided data is seen to lead to promising identification results. Through these identification trials it is shown that the three reaction model best captures the dynamics of the system. This three reaction model serves as the basis for subsequent steady state optimality and sensitivity analysis. From these efforts it is shown that the predicted optimal curves match literature data very well but uncertainty in certain key parameter estimates lead to highly sensitive model predictions (and therefore low confidence). This leads to the conclusion that the developed model is capable of predicting the kinetics of <em>Chlorella</em> digestion but additional trials are needed to further refine the model fitting results.</p> <p>Coupling an anaerobic digester to a microalgal culture is currently considered one of the most promising avenues towards the production of renewable bioenergy, either in the form of biodiesel or biogas. Accurate mathematical models are crucial tools to assess the potential of such coupled biotechnological processes and help optimize their design, operation and control. This paper focuses on the compartment of anaerobic digestion of microalgae. Using experimental data for the anaerobic digestion of <em>Chlorella vulgaris</em>, a grey-box model is developed that allows good prediction capabilities and retains low complexity. The proposed methodology proceeds in two steps, namely a structural and a parametric identification steps. The fitted model is then used to conduct preliminary optimization for the production of biogas from <em>Chlorella vulgaris</em>. The results provide some insight into the potential for bioenergy production from the digestion of microalgae and, more generally, the coupled process.</p> / Master of Applied Science (MASc)
9

Tratamento de lixiviados de aterros sanitários em sistema de reatores anaeróbio e aeróbio operados em batelada seqüencial / Landfill leachate treatment in sequence anaerobic and aerobic batch reactors systems

Contrera, Ronan Cleber 06 June 2008 (has links)
Este trabalho avaliou a tratabilidade dos lixiviados do aterro sanitário de São Carlos-SP, utilizando-se reatores biológicos. O experimento foi conduzido à temperatura ambiente, em uma unidade piloto construída no aterro sanitário de São Carlos-SP. Inicialmente foram testados e comparados dois tipos de reatores anaeróbios, cada um com volume total de 1.200 L e ambos providos de agitação mecânica, diferenciando-se pelo tipo de imobilização da biomassa, sendo o primeiro com biomassa auto-imobilizada (ASBR) e o segundo com biomassa imobilizada em espuma de poliuretano (ASBBR). Um filtro biológico anaeróbio contínuo de fluxo ascendente de aproximadamente 120 L também foi avaliado. Além do pré-tratamento anaeróbio, foi avaliado também o pós-tratamento, que consistiu em um sistema de lodos ativados em batelada seqüencial de aproximadamente 180 L. O ASBR, inoculado com lodo granular de reator UASB, apresentou-se ineficiente, com problemas de desagregação e sedimentação da biomassa. O ASBBR, inoculado com lodo proveniente do fundo de uma lagoa de lixiviados, ao final de sua adaptação, apresentou eficiências superiores a 70%, em termos de remoção de DQO, utilizando-se lixiviado sem diluição, com DQO afluente da ordem de 11.000 mg/L, relação AVT/DQO aproximadamente igual a 0,6 e tempo de reação igual a 7 dias. Verificou-se que a biodegradabilidade anaeróbia dos lixiviados está diretamente relacionada à relação AVT/DQO, e que para relações AVT/DQO Total inferiores a 0,25, a biodegradabilidade é baixa, para relações entre 0,25 e 0,40 é média, e acima de 0,40 pode ser considerada elevada. Observou-se também que concentrações de N-amoniacal, da ordem de até 4.500 mg/L, não impedem o tratamento anaeróbio, desde que a biomassa esteja devidamente adaptada. Aos perfis temporais de concentração, realizados no ASBBR, foi ajustado um modelo de primeira ordem para consumo de substrato, na forma de DQO Total, obtendo valores de K1 variando entre 3,18 x \'10 POT.-5\' e 5,82 x \'10 POT.-5\' /(d.mgSTV/L). O pós-tratamento dos efluentes do ASBBR foi avaliado em um sistema de lodos ativados em batelada seqüencial, que obteve eficiência máxima da ordem de 30% em termos de remoção de DQO, com DQO afluente da ordem de 5.000 mg/L. Quanto ao filtro biológico anaeróbio de fluxo ascendente, obteve-se eficiências superiores a 70%, ao ser alimentado com uma mistura de lixiviado recalcitrante e etanol acidificado, com DQO afluente da ordem de 20.000 mg/L. / This work evaluated the tractability of landfill leachate from São Carlos-SP, utilizing biological reactors. The experiment was conducted at environmental temperature, in a pilot scale unity constructed into the São Carlos-SP landfill area. Initially, it was compared and tested two kinds of anaerobic reactors, each one with 1.200 L of total volume and both provided of mechanical agitation, differing by the kind of biomass immobilization, having the first (ASBR), self-immobilized biomass, and the second (ASBBR), immobilized biomass in polyurethane foam cubes. An approximately 120 L volume continuous up flow anaerobic biofilter was also evaluated. Additionally to the anaerobic treatment, it was also evaluated the post-treatment of landfill leachate in a sequence batch activated sludge system of 180 L. The ASBR, inoculated with a granular UASB sludge from a poultry wastewater treatment, was inefficient and presented sludge segregation and sedimentation problems. The ASBBR, inoculated using the sludge from the bottom of a landfill leachate reservoir, at the final of acclimation, presented efficiency over 70%, in terms of COD removal, utilizing landfill leachate without water dilution, with an inlet COD at the range of 11,000 mg/L, a TVA/COD ratio of approximately 0.6 and reaction time equal to 7 days. It was realized that the landfill leachate anaerobic biodegradability has a directly relationship to the TVA/COD ratio, and for TVA/COD Total ratio lower than 0.25, the biodegradability is low, for ratios between 0.25 and 0.40 is medium, and up to 0.40 may be considered high. It was also observed that \'NH IND.4\' POT.+\' concentrations at the range of 4,500 mg N/L has no significant interference in the anaerobic treatment, since the biomass has properly acclimated. At the temporal profiles of concentration performed in the ASBBR, it was adjusted a first order model for the substrate consumption, in terms of COD Total, obtaining K1 values ranging between 3.18 x \'10 POT.-5\' and 5.82 x \'10 POT.-5\' /(d.mgSTV/L). The post-treatment of the ASBBR effluents was evaluated in a sequence batch activated sludge system, which has obtained maximum efficiencies at the range of 30% in terms of COD removal, with an inlet COD at the range of 5,000 mg/L. As regards of the continuous up flow anaerobic biofilter, it has obtained efficiencies superiors to 70% when fed by a mixing of recovery landfill leachate and acidified ethanol, with an inlet COD at the range of 20,000 mg/L.
10

Tratamento de lixiviados de aterros sanitários em sistema de reatores anaeróbio e aeróbio operados em batelada seqüencial / Landfill leachate treatment in sequence anaerobic and aerobic batch reactors systems

Ronan Cleber Contrera 06 June 2008 (has links)
Este trabalho avaliou a tratabilidade dos lixiviados do aterro sanitário de São Carlos-SP, utilizando-se reatores biológicos. O experimento foi conduzido à temperatura ambiente, em uma unidade piloto construída no aterro sanitário de São Carlos-SP. Inicialmente foram testados e comparados dois tipos de reatores anaeróbios, cada um com volume total de 1.200 L e ambos providos de agitação mecânica, diferenciando-se pelo tipo de imobilização da biomassa, sendo o primeiro com biomassa auto-imobilizada (ASBR) e o segundo com biomassa imobilizada em espuma de poliuretano (ASBBR). Um filtro biológico anaeróbio contínuo de fluxo ascendente de aproximadamente 120 L também foi avaliado. Além do pré-tratamento anaeróbio, foi avaliado também o pós-tratamento, que consistiu em um sistema de lodos ativados em batelada seqüencial de aproximadamente 180 L. O ASBR, inoculado com lodo granular de reator UASB, apresentou-se ineficiente, com problemas de desagregação e sedimentação da biomassa. O ASBBR, inoculado com lodo proveniente do fundo de uma lagoa de lixiviados, ao final de sua adaptação, apresentou eficiências superiores a 70%, em termos de remoção de DQO, utilizando-se lixiviado sem diluição, com DQO afluente da ordem de 11.000 mg/L, relação AVT/DQO aproximadamente igual a 0,6 e tempo de reação igual a 7 dias. Verificou-se que a biodegradabilidade anaeróbia dos lixiviados está diretamente relacionada à relação AVT/DQO, e que para relações AVT/DQO Total inferiores a 0,25, a biodegradabilidade é baixa, para relações entre 0,25 e 0,40 é média, e acima de 0,40 pode ser considerada elevada. Observou-se também que concentrações de N-amoniacal, da ordem de até 4.500 mg/L, não impedem o tratamento anaeróbio, desde que a biomassa esteja devidamente adaptada. Aos perfis temporais de concentração, realizados no ASBBR, foi ajustado um modelo de primeira ordem para consumo de substrato, na forma de DQO Total, obtendo valores de K1 variando entre 3,18 x \'10 POT.-5\' e 5,82 x \'10 POT.-5\' /(d.mgSTV/L). O pós-tratamento dos efluentes do ASBBR foi avaliado em um sistema de lodos ativados em batelada seqüencial, que obteve eficiência máxima da ordem de 30% em termos de remoção de DQO, com DQO afluente da ordem de 5.000 mg/L. Quanto ao filtro biológico anaeróbio de fluxo ascendente, obteve-se eficiências superiores a 70%, ao ser alimentado com uma mistura de lixiviado recalcitrante e etanol acidificado, com DQO afluente da ordem de 20.000 mg/L. / This work evaluated the tractability of landfill leachate from São Carlos-SP, utilizing biological reactors. The experiment was conducted at environmental temperature, in a pilot scale unity constructed into the São Carlos-SP landfill area. Initially, it was compared and tested two kinds of anaerobic reactors, each one with 1.200 L of total volume and both provided of mechanical agitation, differing by the kind of biomass immobilization, having the first (ASBR), self-immobilized biomass, and the second (ASBBR), immobilized biomass in polyurethane foam cubes. An approximately 120 L volume continuous up flow anaerobic biofilter was also evaluated. Additionally to the anaerobic treatment, it was also evaluated the post-treatment of landfill leachate in a sequence batch activated sludge system of 180 L. The ASBR, inoculated with a granular UASB sludge from a poultry wastewater treatment, was inefficient and presented sludge segregation and sedimentation problems. The ASBBR, inoculated using the sludge from the bottom of a landfill leachate reservoir, at the final of acclimation, presented efficiency over 70%, in terms of COD removal, utilizing landfill leachate without water dilution, with an inlet COD at the range of 11,000 mg/L, a TVA/COD ratio of approximately 0.6 and reaction time equal to 7 days. It was realized that the landfill leachate anaerobic biodegradability has a directly relationship to the TVA/COD ratio, and for TVA/COD Total ratio lower than 0.25, the biodegradability is low, for ratios between 0.25 and 0.40 is medium, and up to 0.40 may be considered high. It was also observed that \'NH IND.4\' POT.+\' concentrations at the range of 4,500 mg N/L has no significant interference in the anaerobic treatment, since the biomass has properly acclimated. At the temporal profiles of concentration performed in the ASBBR, it was adjusted a first order model for the substrate consumption, in terms of COD Total, obtaining K1 values ranging between 3.18 x \'10 POT.-5\' and 5.82 x \'10 POT.-5\' /(d.mgSTV/L). The post-treatment of the ASBBR effluents was evaluated in a sequence batch activated sludge system, which has obtained maximum efficiencies at the range of 30% in terms of COD removal, with an inlet COD at the range of 5,000 mg/L. As regards of the continuous up flow anaerobic biofilter, it has obtained efficiencies superiors to 70% when fed by a mixing of recovery landfill leachate and acidified ethanol, with an inlet COD at the range of 20,000 mg/L.

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