Ángeles Val del Río

University of Santiago de Compostela, Santiago, Galicia, Spain

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Publications (20)30.78 Total impact

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    ABSTRACT: The activated sludge process (AS) is still nowadays the most applied one in wastewater treatment plants (WWTP). This technology evolved throughout this last century into multiple configurations to achieve organic matter (COD, BOD5, etc.) and nutrients (nitrogen and phosphorous) removal. However, the severe increases of energy and sludge management costs registered in the last decades are boosting the research in the quest for more sustainable and efficient processes. The energetic demand of the AS, when nitrogen removal is required, varies typically in the range from 0.5 to 1.4 kWh/m3 of treated water (Lazarova et al., 2012). The AS is based on aeration to catalyse biological processes and it does not take advantage of the potential energy contained in the organic matter present in the wastewater. The energetic potential of every kilogram of organic matter oxidized (as COD) is about 4 kWh (Garrido et al., 2013). Considering 250 litres of wastewater and 60 g of organic matter (as BOD5) per inhabitant equivalent and day, about 1 kWh/m3 of wastewater could potentially be produced. In order to profit from this potential energy production the future of the wastewater treatment should be focused on anaerobic processes, for both organic matter and nitrogen removal. These processes present higher efficiency and sustainability in terms of biomass growth (the yields are at least one order of magnitude lower) and energy requirements compared to aerobic ones. The energy will be produced by anaerobic digestion of the organic matter. For the nitrogen removal the discovery of anammox bacteria in the nineties opened the possibility to shortcut the nitrogen cycle which involved the decrease of oxygen requirements due to the partial nitrification of half of the ammonium to nitrite while organic matter is not required for denitrification. The company aqualia GIA with the know-how of the University of Santiago de Compostela (USC) developed the so called ELAN® process which performs autotrophic nitrogen removal in a single granular biomass sequencing batch reactor (SBR) (Vazquez-Padin et al, in press). Around 20% of the nitrogen load in municipal WWTP comes from the supernatant of the anaerobic sludge digester. Nitrogen removal rates of 0.5 – 1.0 kg N/(m3 d) are achieved when the ELAN® process (Figure 1a) is applied for the treatment of the digester supernatant. The introduction of the ELAN® process in the sludge line is already a mature technology that brings WWTP closer to energy autarky (Siegrist et al., 2008). The next step and challenge will be the direct application of the anaerobic digestion process in the mainstream followed by the ELAN® process (Figure 1b). This treatment strategy will switch the paradigm and transform municipal and industrial WWTP from energy consumers to energy producers. Laboratory and pilot scale reactors are being run in the USC and in Guillarei WWTP respectively, to study the applicability of the autotrophic nitrogen removal ELAN® process (Figure 2) to mainstream conditions, i.e., low temperature and low ammonia concentration.
    Activated Sludge – 100 Years and Counting!, Essen, Germany; 06/2014
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    ABSTRACT: BACKGROUND Management of the sludge generated in the wastewater treatment plants accounts for more than 50% of their operational costs. To minimise these costs, technologies capable of reducing the production of sludge in the plant need to be developed, such as aerobic granular systems. The aggregation state of aerobic granular sludge (AGS) could be a limiting factor for its further anaerobic digestion. Therefore in this work the feasibility of anaerobic digestion of AGS has been studied under three conditions: (1) raw AGS, (2) thermal pre-treated AGS and (3) a mixture of thermal pre-treated AGS with primary sludge. RESULTS The values obtained for anaerobic biodegradability and reduction of solids in the case of raw AGS were 44% and 32%, respectively. Thermal pre-treatment of AGS at 133 °C enhanced the anaerobic digester performance, in terms of solids reduction, by approximately 47%. The mixture of thermal pre-treated AGS with primary sludge provided better results for solids removal than in the case with only thermal pre-treated AGS. CONCLUSION Anaerobic digestion of AGS has a similar performance as that reported for waste activated sludge, which indicates that the aggregation of the biomass into granules does not seem to limit the anaerobic process.
    Journal of Chemical Technology & Biotechnology 05/2014; DOI:10.1002/jctb.4171 · 2.49 Impact Factor
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    ABSTRACT: Poster: Application of aerobic granular pilot scale SBR plant to treat swine slurry wastewaters. Conference: EcoTechnologies for Wastewater Treatment. ECO STP. Santiago de Compostela June, 2012.
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    ABSTRACT: The presence of salts in wastewaters is common in coastal areas, where leakages of salty water occur into the sewage systems, but also when the industrial process involves the use of salts or seawater. Aerobic granular systems can be suitable to treat brackish wastewaters as an alternative to activated sludge ones since the high biomass concentrations make up for the decrease of the activity due to salt presence. These granular systems have also as advantage the lower amount of sludge generated in comparison with the activated sludge ones but, in both cases, the excess of sludge produced needs to be post-treated. Anaerobic digestion is normally used to reduce the concentration of solids and to produce biogas. To the present, the effect of saline conditions in anaerobic digestion was preferentially studied in systems treating wastewaters but scarcely revised when treating sewage sludge. The aim of this work is to determine the feasibility, under brackish conditions, of the anaerobic biodegradability of the aerobic granular sludge (AGS) and to compare the results with the anaerobic digestion of flocculent activated sludge (FLAS). The results showed that the biodegradabilities of AGS (32%) and FLAS (27%) were similar, which indicates that the aggregation state of the substrate did not limit the process. Brackish conditions led to a concentration of sodium and free sulphide (FS) inside the reactor in the range of 2.1-5.2 g L-1 and 38-93 mg L-1 respectively, that are within the inhibitory levels reported for the anaerobic treatment of wastewaters. However, the biomethane potential and biodegradability obtained in this work indicated that neither sodium nor free sulphide had an inhibitory effect at these concentrations. The content of H2S in the biogas was relevant (1.5-3.8%) and its pre-treatment is needed if the biogas is going to have any further use, i.e., in energy production.
    Chemical Engineering Journal 09/2013; 231:449-454. DOI:10.1016/j.cej.2013.07.052 · 4.32 Impact Factor
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    ABSTRACT: A pilot-scale Sequencing Batch Reactor was operated during 307 days in order to treat swine slurry characterized by its high variable composition: organic and nitrogen applied loading rates and C/N ratio were 1.4–6.3 kg CODs/(m3 d), 0.5–2.5 kg N/(m3 d) and 1.9–9.4 g CODs/(g N), respectively. Aerobic granules successfully developed in the reactor and their physical properties remained rather stable despite the feeding composition variability. Organic and ammonia removal efficiency reached 61–73% and 56–77%, respectively, however ammonia was mainly oxidized to nitrite. The reactor had a good biomass retention capacity to select for granular biomass. However, its efficiency to retain the solids present in the feeding was low. Aerobic granulation in SBR systems appears as an interesting alternative to treat slurry in small livestock facilities where the implementation of anaerobic digestion systems is not a feasible option or the removal of nitrogenous compounds is required.
    PROCESS BIOCHEMISTRY 08/2013; DOI:10.1016/j.procbio.2013.06.004 · 2.52 Impact Factor
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    ABSTRACT: Nowadays, Anammox based processes have been successfully applied to high temperature and ammonia loaded streams. However, the application of such processes to the main stream of WWTPs opens the possibility of removing the nitrogenous compounds with less energy and chemicals requirements. Furthermore more organic matter is available for methane production. In this work the long-term performance and stability of a CANON system operated at 20 and 15 ºC was researched. When the system was fed with a medium containing 200 mg NH4+-N/L, nitrogen removal rates of 0.45 and 0.33 g N/L•d were achieved at 20 and 15 ºC, respectively, and the operation was stable. However, when the inlet ammonia concentration was decreased to 70 mg NH4+-N/L (15 ºC), the nitrogen removal rate was of only 0.05 g N/L•d limited by the low dissolved oxygen level maintained in the bulk liquid in order to avoid nitrite oxidation.
    13th World Congress on Anaerobic Digestion, Santiago de Compostela; 06/2013
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    ABSTRACT: The aerobic granular systems are mainly sequencing batch reactors where the biomass is submitted to feast-famine regimes to promote its aggregation in the form of granules. In these systems, different cycle distributions can be applied for the simultaneous removal of organic matter, nitrogen and phosphorus. In this work two strategies were followed in order to evaluate the effects of the cycle distribution. In the first experiment, the length of the operational cycle was decreased in order to maximize the treatment capacity and consequently the famine/feast ratio was also decreased. In the second experiment, an initial anoxic phase was implemented to improve nitrogen removal efficiency. The results obtained showed that to reduce the famine/feast ratio from 10 to 5 was possible by increasing the treated organic and nitrogen loading rates in the system to 33%, without affecting the removal efficiencies of organic matter (97%) and nitrogen (64%) and producing a slight detriment of the granules characteristics. On the other hand, the implementation of an anoxic phase of 30 min previous to the aerobic one with a pulse-fed mode increased the nitrogen removal of pig manure from 20 to 60%, while the cycle configuration comprising a continuous feeding simultaneous with an anoxic phase of 60 min did not enhance the nitrogen removal and even worsen the ammonia oxidation.
    Environmental Technology 06/2013; 34(9-12):1463-72. DOI:10.1080/09593330.2012.753470 · 1.20 Impact Factor
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    ABSTRACT: Aerobic granular sludge is presented as an alternative technology to conventional activated sludge processes for the treatment of low-strength wastewaters. Results obtained with granular aerobic reactors at laboratory scale are promising but, there are few studies carried out at pilot scale. Therefore, more information about the stability of granules and their performance at larger scale is needed to establish if aerobic granulation could be a feasible treatment. With this aim, a 100 L granular sequencing batch reactor (GSBR) operating at high loading rate and treating low-strength wastewater for simultaneous carbon, nitrogen and phosphorus removal was operated for 11 months. Mature granules prevailed in the GSBR during a period of 5 months (from days 150 to 330), with a SVI30 of 13 ± 6 mL g−1 TSS, a granule density around 114 ± 5 g TSS L−1 and an average particle size of 2.4 mm. The biological nitrogen removal with mature granules was mainly performed via nitrite, probably due to the large granule size achieved. Nitrification efficiency was higher than 75% and occurred simultaneously with denitrification during the aerobic phase of the GSBR. A progressive accumulation of P-salts (probably apatite), was found from days 150 to 300, which could enhance the destabilization of granules at the end of the experimental period.
    Chemical Engineering Journal 08/2012; 198-199:163-170. DOI:10.1016/j.cej.2012.05.066 · 4.32 Impact Factor
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    ABSTRACT: The first studies about granular biomass developed in aerobic conditions are dated in the early 90’s. Mishima and Nakamura (1991) developed aerobic granules in a UASB type reactor using pure oxygen. This work was not really appreciated at that moment and it was in the late 90’s when extensive research was performed in this field. In these systems the simultaneous removal of organic matter, nitrogen and phosphorus compounds from wastewater can be developed (de Kreuk et al., 2005a). From the carried out research it has been found that aerobic granular systems present several advantages compared to conventional activated sludge such as excellent settling properties of the biomass, large biomass retention, the ability to withstand shock and toxic loadings, the presence of aerobic and anoxic zones inside the granules to perform different biological processes, etc. (Morgenroth et al., 1997; Dangcong et al., 1999; Beun et al. 1999; Peng et al. 1999; Tay et al. 2001a; Lin et al. 2003; Liu et al., 2003; Yang et al., 2003; Arrojo et al., 2004; Campos et al., 2009).
    Innovative Technologies for Urban Wastewater Treatment Plants (2nd Edition)., 2nd edited by Francisco Omil, Sonia Suárez, 07/2012: chapter Aerobic granulation technology .: pages 39-62; Lápices 4., ISBN: 13-978-84-695-3514-1
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    ABSTRACT: Abstract BACKGROUND: Technologies based on aerobic granular biomass are presented as a new alternative application to wastewater treatment due to its advantages in comparison with the conventional activated sludge processes. However, the properties of the aerobic granules can be influenced by the presence of residual amounts of coagulant-flocculant reagents, frequently used as pre-treatment before the biological process. In this work the effect of these compounds on aerobic granular biomass development was tested. RESULTS: The presence of coagulant-flocculant reagents led to a worse biomass retention capacity with a lower VSS concentration compared with a control reactor (4.5 vs. 7.9 g VSS L−1) and with a higher SVI (70 vs. 40 mL [g TSS]−1) and diameter (5.0 vs. 2.3 mm). These reagents also caused a decrease in the maximum oxygen consumption rate, but the removal efficiencies of organic matter (90%) and nitrogen (60%) achieved were similar to those in the control reactor. CONCLUSION: The continuous presence of residual levels of coagulant-flocculant reagents from the pre-treatment unit negatively affected the formation process and the physical properties of the aerobic granules; however, the removal of organic matter and nitrogen were not affected. Copyright © 2012 Society of Chemical Industry
    Journal of Chemical Technology & Biotechnology 07/2012; 87(7):908. DOI:10.1002/jctb.3698 · 2.49 Impact Factor
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    ABSTRACT: Full Paper Published in: Operation of an aerobic granular pilot scale SBR plant to treat swine slurry: Process Biochemistry 08/2013; DOI:dx.doi.org/10.1016/j.procbio.2013.06.004 A pilot-scale Sequencing Batch Reactor was operated in order to remove organic matter and nutrients from pig slurry with high variable composition. Aerobic granules grew successfully in the reactor in the first weeks of operation. The characteristics of the biomass remained rather stable during the long term operation of the reactor (307 days) despite the high variation in the Organic and Nitrogen Loading Rates, which varied from 1.4 to 6.3 kg CODs/(m3·d) and from 0.5 to 2.5 kg N/(m3·d), respectively. Furthermore the C/N ratio also varied in a wide range (1.9-9.4 g CODs/g N). The reactor had a good biomass retention capacity to select for granular biomass. Hhowever, it was not able to retain the colloidal solids that were fed to the reactor, as consequence, the VSS concentration in the effluent was almost the same that those in the influent.
    Ecotechnologies for Wastewater Treatment 2012 International Conference; 06/2012
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    ABSTRACT: The aerobic granular systems are a good alternative to the conventional activated sludge (AS) ones to reduce the production of sludge generated in wastewater treatment plants (WWTP). Although the quantity of produced sludge is low its post-treatment is still necessary. In the present work the application of the anaerobic digestion combined with a thermal pre-treatment was studied to treat two different aerobic granular biomasses: one from a reactor fed with pig manure (G1) and another from a reactor fed with a synthetic medium to simulate an urban wastewater (G2). The results obtained with the untreated aerobic granular biomasses showed that their anaerobic biodegradability (BD) (33% for G1 and 49% for G2) was similar to that obtained for an activated sludge (30-50%) and demonstrate the feasibility of their anaerobic digestion. The thermal pre-treatment before the anaerobic digestion was proposed as a good option to enhance the BD when this was initially low (33% G1) with an enhancement between 20% at 60 °C and 88% at 170 °C with respect to the untreated sludge. However when the initial BD was higher (49% G2) the thermal pre-treatment produced a slight improvement in the methane production (14% and 18%) and at high temperatures (190 and 210 °C) which did not justify the application of such a treatment.
    Water Research 09/2011; 45(18):6011-20. DOI:10.1016/j.watres.2011.08.050 · 5.32 Impact Factor
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    ABSTRACT: Enmarcado en los proyectos "NOVEDAR_Consolider" y Togransys, la Universidad de Santiago de Compostela ha realizado un estudio sobre la aplicación de reactores SBR (Sequencing Batch Reactor) en el tratamiento de efluentes generados en granjas ganaderas. No es difícil encontrar este tipo de sistemas en plantas de tratamiento de aguas residuales de origen urbano e industrial, pero su aplicación en el caso de la fracción líquida de los purines es actualmente muy limitada. La investigación realizada ha demostrado la efectividad de un reactor SBR operado en condiciones aerobias y conteniendo biomasa en forma de gránulos, como método de tratamiento de estos efluentes, que permite eliminar de forma conjunta la materia orgánica y el nitrógeno. El siguiente paso de la investigación supondrá la puesta en marcha de una planta a escala piloto, de manera que se puedan establecer las condiciones de operación óptimas para el tratamiento de la fracción líquida de purines directamente en la granja en un sistema SBR aerobio con biomasa granular.
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    ABSTRACT: Aerobic granulation is a promising technology for the removal of nutrients in wastewater. Since research to date is mainly focused at laboratory scale, a pilot-scale sequencing batch reactor (100 L) was operated to obtain granular sludge in aerobic conditions grown on acetate as organic carbon substrate. Selective pressure created by means of decreasing settling time and increasing organic loading rate (OLR) enhanced the formation of aerobic granular sludge. Granules appeared after 6 days and reached an average diameter around 3.5 mm. The settling velocity value should be higher than 11 m h−1 in order to remove flocculent biomass. The reactor treated OLRs varying between 2.5 and 6.0 g COD L−1 d−1 reaching removal efficiencies around 96%, which demonstrates the high activity and the ability of the system to withstand high OLR. Nevertheless, a rapid increase in the OLR produced a loss of biomass in the reactor due to breakage of the granules. Copyright © 2011 Society of Chemical Industry
    Journal of Chemical Technology & Biotechnology 05/2011; 86(5):763 - 768. DOI:10.1002/jctb.2589 · 2.49 Impact Factor
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    ABSTRACT: Los purines son generalmente tratados con sistemas biológicos anaerobios que eliminan la materia orgánica convirtiéndola en biogás. Sin embargo, los efluentes generados tienen una alta concentración de nitrógeno. Desde un punto de vista económico, la eliminación de nitrógeno en esta corriente mediante un proceso convencional de nitrificación-desnitrificación es costosa debido a que se necesitaría añadir una fuente externa de materia orgánica. El descubrimiento del proceso anammox abre nuevas alternativas más económicas para la eliminación de nitrógeno. En este proceso se combinan amonio y nitrito para producir nitrógeno gas por lo que se necesita una etapa de nitrificación parcial previa en la que se oxide el 50% del amonio a nitrito. Ambos procesos, nitrificación parcial y anammox, podrían realizarse también simultáneamente en una única unidad bajo condiciones microaerobias (sistema CANON).
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    ABSTRACT: Four lab scale sequencing batch reactors (SBRs) were operated to remove organic matter and nitrogen from four different industrial wastewaters. The biomass grew in the reactors in the form of aerobic granules characterized by good settling properties. The high biomass concentrations achieved inside the reactors allowed reducing the solids concentration in the effluent down to 0.2 g VSS L(-1). The organic loading rates (OLR) applied to reactors ranged between 0.7 and 5.0 g CODL(-1)d(-1) with removal efficiencies of 60-95%. The nitrogen loading rates (NLR) applied varied between 0.15 and 0.65 g NH(4)(+)-NL(-1)d(-1) with variable removal efficiencies in the four systems (between 15% and 76%).
    Journal of Environmental Management 04/2011; 95 Suppl:S88-92. DOI:10.1016/j.jenvman.2011.03.019 · 3.19 Impact Factor
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    ABSTRACT: Aerobic granular sludge grown in a sequential batch reactor was proposed as an alternative to anaerobic processes for organic matter and nitrogen removal from swine slurry. Aerobic granulation was achieved with this wastewater after few days from start-up. On day 140 of operation, the granular properties were: 5 mm of average diameter, SVI of 32 mL (g VSS)(-1) and density around 55 g VSS (L(granule))(-1). Organic matter removal efficiencies up to 87% and nitrogen removal efficiencies up to 70% were achieved during the treatment of organic and nitrogen loading rates (OLR and NLR) of 4.4 kg COD m(-3) d(-1) and of 0.83 kg N m(-3) d(-1), respectively. However, nitrogen removal processes were negatively affected when applied OLR was 7.0 kg COD m(-3) d(-1) and NLR was 1.26 kg N m(-3) d(-1). The operational cycle of the reactor was modified by reducing the volumetric exchange ratio from 50 to 6% in order to be able to treat the raw slurry without dilution.
    Water Science & Technology 01/2011; 63(9):1808-14. DOI:10.2166/wst.2011.381 · 1.21 Impact Factor
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    ABSTRACT: An airlift reactor using zeolite particles as carrier material was used for the nitrification of effluents from the aquaculture industry. During the start-up the nitrogen concentration was kept around 100 mg NH4(+)-N/L to develop the nitrifying population. Later it was decreased down to around 3 mg NH4(+)-N/L and the dilution rate was increased up to 4.8 d(-1) in order to simulate the conditions in a an aquaculture waster treatment system. A nitrogen loading rate (NLR) of 535 mg NH(+)-N/m2 d was fully oxidized to nitrate. Higher values of NLRs caused nitrite accumulation. A second biofilm reactor was fed with a synthetic medium containing 50 mg NH4(+)-N/L which simulated the effluents from anaerobic units treating domestic wastewater. A nitrogen loading rate of 400 mg NH4(+)-N/L d was oxidized into nitrate with an efficiency of 60% at a dilution rate of 8 d(-1). Both biofilm systems allowed the development of a nitrifying population to treat the studied types of wastewaters.
    Water Science & Technology 01/2011; 63(9):1880-6. DOI:10.2166/wst.2011.400 · 1.21 Impact Factor
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    ABSTRACT: The biological treatment of wastewater is often accomplished by means of conventional activated sludge systems that generally require large surface area for implantation. This is caused by the relatively poor settling characteristics of activated sludge, resulting in low solids concentrations inside the aeration tanks and in low maximum hydraulic load of secondary sedimentation tanks. Therefore, the conventional wastewater treatment installations have some inherent disadvantages, like the low volumetric conversion capacities, focussed mainly on the removal of easily degradable organic compounds and the high amounts of sludge production. Due to the sensitivity of nitrifying bacteria to environmental factors, as well as their lower growth rates, it is difficult to obtain and maintain sufficient nitrifying bacteria in conventional wastewater treatment plants. Thus, the nitrification process is the limiting step. This fact provokes the necessity of the use of high solid retention times (SRT) and of the large volume of the system. Therefore, the development of new processes and technologies is required in which the efficient nitrogen removal is obtained together with the organic matter removal. To overcome the drawbacks associated with activated sludge systems, in the 1990s, the use of biofilm systems for aerobic processes was promoted. In such systems, biomass adheres to both fixed and mobile carriers, which allows that the biomass retention time does not depend on the settling characteristics of biomass (Tijhuis et al. 1994). The main feature of these technologies is their ability to treat high volumetric loads, occasionally without an independent sludge/effluent separation step. However, the main disadvantage of these systems is the relatively high investment costs (de Bruin et al. 2004) associated to the necessity of using support materials for the biomass attachment. In order to improve the biofilm technologies and get the benefits of biofilm systems, but without the use of carrier materials, in recent years, research showed that it is possible to grow granular sludge in either continuous or batchwise operated systems.
    Environmental Technologies to Treat Nitrogen Pollution, Edited by Francisco J. Cervantes, 11/2009: chapter Chapter XIII. Nitrogen removal in aerobic granular systems: pages 373-401; IWA Publishing., ISBN: 13 9781843392224
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    ABSTRACT: Aerobic granular sludge is a technology widely studied at laboratory scale which is beginning to be applied for the treatment of urban or industrial wastewater in pilot scale plants. A SBR reactor with a volume of 100 L was used to study the start up and operation of aerobic granular sludge at pilot scale. Efficiencies of 90-95% in terms of organic matter removal were achieved, however aerobic granulation was delayed compared to previous experiences in lab-scale reactors, and the granules presented periods of physical instability associated to aggregates break up.
    3rd International Meeting on Environmental Biotechnology and Engineering; 09/2009