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ABSTRACT: The aim of this study was to elucidate the effect of hydrothermal pretreatment at 25, 100, 150 and 200°C on fibre composition and the biomethane potential of sunflower oil cake (SuOC). An increase in pretreatment temperature from 25 to 200°C caused a decrease in hemicellulose content in the solid pretreated fraction from 13 to 6% while the lignin content increased by 16%. Soluble compounds also increased with temperature. Digestion of solid fractions from pretreatments at 25, 100, 150 and 200°C in batch assays at 35±1°C resulted in methane yields of 114±9, 105±7, 82±7 and 53±8mL CH(4) g(-1)COD(added), respectively. The corresponding methane yields for the liquid fractions were 276±6, 310±4, 220±15 and 247±10mL CH(4) g(-1)COD(added), respectively. Therefore the overall methane yield was highest for SuOC pretreated at 100°C; however, this value was only 6.5% higher than that achieved after pretreatment at 25°C.
Bioresource technology 08/2012; 123:424-9. · 4.25 Impact Factor
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ABSTRACT: Two laboratory-scale anaerobic fixed bed reactors were evaluated while treating dairy manure at upflow mode and semicontinuous feeding. One reactor was packed with a combination of waste tyre rubber and zeolite (R1) while the other had only waste tyre rubber as a microorganism immobilization support (R2). Effluent quality improved when the hydraulic retention time (HRT) increased from 1.0 to 5.5 days. Higher COD, BOD5, total and volatile solids removal efficiencies were always achieved in the reactor R1. No clogging was observed during the operation period. Methane yield was also a function of the HRT and of the type of support used, and was 12.5% and 40% higher in reactor R1 than in R2 for HRTs of 5.5 and 1.0 days, respectively. The results obtained demonstrated that this type of reactor is capable of operating with dairy manure at a HRT 5 times lower than that used in a conventional reactor.
Bioresource Technology 11/2008; 99(15):7412-7. · 4.98 Impact Factor
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ABSTRACT: A study of the effect of organic loading rate on the performance of anaerobic digestion of two-phase olive mill solid residue (OMSR) was carried out in a laboratory-scale completely stirred tank reactor. The reactor was operated at an influent substrate concentration of 162 g chemical oxygen demand (COD) dm−3. The organic loading rate (OLR) varied between 0.8 and 11.0 g COD dm−3 d−1. COD removal efficiency decreased from 97.0% to 82.6% when the OLR increased from 0.8 to 8.3 g COD dm−3 d−1. It was found that OLRs higher than 9.2 g COD dm−3 d−1 favoured process failure, decreasing pH, COD removal efficiency and methane production rates (QM). Empirical equations described the effect of OLR on the process stability and the effect of soluble organic matter concentration on the total volatile fatty acids (TVFA)/total alkalinity (TAlk) ratio (ρ). The results obtained demonstrated that rates of substrate uptake were correlated with concentration of biodegradable COD, through an equation of the Michaelis–Menten type. The kinetic equation obtained was used to simulate the anaerobic digestion process of this residue and to obtain the theoretical COD degradation rates in the reactor. The small deviations obtained (equal to or lower than 10%) between values calculated through the model and experimental values suggest that the proposed model predicts the behaviour of the reactor accurately. Copyright © 2007 Society of Chemical Industry
Journal of Chemical Technology & Biotechnology 03/2007; 82(3):259 - 266. · 2.17 Impact Factor
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ABSTRACT: A study of the anaerobic digestion of wastewater from the pressing of orange peel generated in orange juice production was carried out in a laboratory-scale completely stirred tank reactor at mesophilic temperature (37 degrees C). Prior to anaerobic treatment the raw wastewater was subjected to physicochemical treatment using aluminum sulfate as a flocculant and to pH reduction using a solution of sulfuric acid. The reactor was batch fed at COD loads of 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 g of COD. The process was very stable for all of the loads studied, with mean pH and alkalinity values of 7.5 and 3220 mg of CaCO3/L, respectively. The anaerobic digestion of this substrate was found to follow a first-order kinetic model, from which the specific rate constants for methane production, K(G), were determined. The K(G) values decreased considerably from 0.0672 to 0.0078 L/(g h) when the COD load increased from 1.5 to 5.0 g of COD, indicating an inhibition phenomenon in the system studied. The proposed model predicted the behavior of the reactor very accurately, showing deviations of <5% between the experimental and theoretical values of methane production. The methane yield coefficient was found to be 295 mL of CH4 STP/g of COD removed, whereas the mean biodegradability of the substrate (TOC) was 88.2%. A first-order kinetic model for substrate (TOC) consumption allowed determination of the specific rate constants for substrate uptake, K(C), which also decreased with increasing loading, confirming the above-mentioned inhibition process. Finally, the evolution of the individual volatile fatty acid concentrations (acetic, C2; propionic, C3; butyric, C4; isobutyric, iC4; valeric, C5; isovaleric, iC5; and caproic, C6) with digestion time for all loads used was also studied. The main acids generated were acetic and propionic for all loads studied, facilitating the conversion into methane.
Journal of Agricultural and Food Chemistry 03/2007; 55(5):1905-14. · 2.82 Impact Factor
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ABSTRACT: The new two-phase olive oil mills produce three identifiable and separate waste streams, namely (1) the wash waters from the initial cleansing of the fruit, (2) the aqueous solid residues from the primary centrifugation and (3) the wash waters from the secondary centrifugation. As well as offering process advantages, they also consume less water. Therefore the solid residue, two-phase olive mill solid waste (OMSW), has a high organic matter concentration, giving it an elevated polluting load, and cannot be easily handled by traditional technology which deals with the conventional three-phase olive cake. In addition, the new two-phase olive mill effluents (TPOME) are made up of a mixture of effluents (1) and (3), the total volume of TPOME generated being ∼0.25 dm3 kg−1 olives processed. This review aims to report the main features and characteristics of two-phase OMSW and TPOME as compared with the classical olive cake and olive mill wastewater (OMW) derived from the three-phase manufacturing process. The advantages and disadvantages of the two-phase decanting process are summarised. The anaerobic digestibility of two-phase OMSW using different influent substrate concentrations is reported. Kinetic studies of anaerobic digestion of two-phase OMSW are also reviewed and summarised, as well as mass balances to predict the behaviour of the reactor and simplified kinetic models for studying the hydrolysis, acidogenic and methanogenic steps of one- and two-stage anaerobic digestion of OMSW. The review also includes the following: assays of anaerobic digestion of wastewaters from the washing of olives, of olive oil and the two together using fluidised beds and hybrid reactors; the kinetics, performance, stability, purification efficiencies and methane yield coefficients. Copyright © 2006 Society of Chemical Industry
Journal of Chemical Technology & Biotechnology 08/2006; 81(9):1450 - 1462. · 2.17 Impact Factor
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ABSTRACT: Over the last 10 years the manufacture of olive oil has undergone important evolutionary changes in the equipment used for the separation of olive oil from the remaining components. The latest development has been the introduction of a two-phase centrifugation process in which a horizontally-mounted centrifuge is used for a primary separation of the olive oil fraction from the vegetable solid material and vegetation water. Therefore, the new two-phase olive oil mills produce three identifiable and separate waste streams. These are: 1) the wash waters from the initial cleansing of the fruit; 2) the wash waters from the secondary centrifuge and 3) the aqueous solid residues from the primary centrifugation. As well as offering process advantages they also reduce the water consumption of the mill. The introduction of this technology was carried out in 90% of Spanish olive oil factories. Therefore, the new twophase olive mill effluents (TPOME) are made up of the mixture of effluents (1) and (2), the total volume of TPOME generated being around 0.25 l/kg of olives processed. In addition, the solid residue (two-phase olive pomace, TPOP) has a high organic matter concentration giving an elevated polluting load and it cannot be easily handled by traditional technology which deals with the conventional three-phase olive cake.
So, this paper aims to report the main features and characteristics of TPOME, and of TPOP, as compared to the classical olive mill wastewater (OMW) and olive cake derived from the three-phase manufacturing process. The advantages and disadvantages of the two-phase decanting process will be summarized. Among the treatments reported for TPOME, aerobic processes in completely mixed and activated sludge reactor showed high COD removal efficiencies. Kinetic constants of the aerobic processes were also compared at different operational conditions. The report also includes the following findings: assays of anaerobic digestion of wastewaters from the washing of olives, of olive oil and the two together using fluidised-beds and hybrid reactors; the kinetics, performance, stability, purification efficiencies and methane yield coefficients; other purifying methods for TPOME treatment including oxidation (with different chemical oxidants) and physico-chemical treatments (using different coagulants and flocculants); the anaerobic digestibility of TPOP using different influent substrate concentrations; kinetic studies of anaerobic digestion of TPOP and mass balances to predict the behaviour of the reactor and simplified kinetic models for studying the hydrolysis, acidogenic and methanogenic steps of one and two-stage anaerobic digestion of TPOP. Finally, other methods for treatment and use of TPOP were mentioned, including composting, production of alcohols, mannitol, and other added - value compounds such as monosaccharides, oligosaccharides, arabinose and glucose. Furfural and activated carbons were also produced from TPOP and included in the report.
Durante los últimos 10 años el proceso de elaboración de aceite de oliva ha sufrido importantes cambios en los equipos utilizados para la separación del aceite del resto de componentes. El más reciente ha sido la introducción del decanter o centrífuga horizontal de dos fases para la separación del aceite de oliva de la mezcla constituida por la fracción sólida vegetal y agua de vegetación. Por tanto, el sistema de elaboración por centrifugación en dos fases genera tres residuos diferentes: 1) aguas de lavado de aceitunas; 2) aguas de lavado de aceite obtenidas en la centrífuga vertical y 3) residuos sólidos con un elevado contenido en humedad procedente del decanter. Entre otras ventajas, el proceso de dos fases también reduce considerablemente el consumo de agua de proceso. Esta tecnología ya se ha introducido en el 90% de las almazaras españolas. Por tanto, los nuevos efluentes líquidos resultantes del proceso en dos fases están constituidos por la mezcla de los efluentes (1) y (2), generándose cantidades del orden de 0.25 l/kg de aceitunas procesadas. De manera adicional, se genera un nuevo residuo sólido (orujo húmedo o “alperujo”) con una elevada concentración de materia orgánica, lo que le confiere un alto poder contaminante, dificultando su manipulación y aprovechamiento mediante los métodos tradicionales aplicados al orujo convencional de tres fases.
En este trabajo se detallan las características principales y propiedades de los efluentes líquidos y residuos sólidos resultantes del proceso de elaboración del aceite de oliva en dos fases, comparándose con las características de los alpechines y orujos tradicionales procedentes del sistema de tres fases. También se resumen las ventajas e inconvenientes del sistema de dos fases. Entre los tratamientos que se detallan para la depuración de las aguas de lavado mezcla, destacan los procesos aerobios en reactores de mezcla completa y lodos activados, con los que se alcanzan elevadas eficiencias de depuración, obteniéndose las constantes cinéticas de los mismos para diferentes condiciones operacionales. También se describen los resultados más relevantes obtenidos en el proceso de digestión anaerobia de estas aguas de lavado utilizando reactores de lecho fluidizado e híbridos, detallándose el comportamiento operacional, estabilidad, eficiencias de depuración y coeficientes de rendimiento en metano alcanzados. Igualmente se detallan otros métodos de tratamiento del alperujo, tales como métodos oxidativos (utilizando diferentes oxidantes químicos) y fisicoquímicos (utilizando diferentes coagulantes y floculantes). Al mismo tiempo, se describe la digestibilidad anaerobia del alperujo utilizando diferentes concentraciones de sustrato como alimento, detallándose algunos estudios cinéticos y balances de masa que permiten reproducir el comportamiento del reactor, así como determinados modelos simplificados que permiten estudiar las etapas de hidrólisis, acidogénesis y metanogénesis en el proceso de digestión anaerobia en una y dos etapas del alperujo. Finalmente, se reseñan otros métodos para el tratamiento y aprovechamiento de este residuo, tales como compostaje, obtención de alcoholes, manitol, y otros compuestos de valor añadido, tales como monosacáridos, oligosacáridos, arabinosa y glucosa, así como furfural y carbón activo.
Grasas y Aceites. 01/2006;
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ABSTRACT: A comparative kinetic study was carried out on the anaerobic digestion of two-phase olive mill effluent (TPOME) using three 1-dm3 volume stirred tank reactors, one with freely suspended biomass (control), and the other two with biomass supported on polyvinyl chloride (PVC) and bentonite (aluminium silicate), respectively. The reactors were batch fed at mesophilic temperature (35 °C) using volumes of TPOME of between 50 and 600 cm3, corresponding to chemical oxygen demand (COD) loadings in the range of 1.02–14.22 g, respectively. The process followed first-order kinetics and the specific rate constants, K0, were calculated. The K0 values decreased considerably from 2.59 to 0.14 d−1, from 1.93 to 0.23 d−1 and from 1.52 to 0.17 d−1 for the reactors with suspended biomass (control) and biomass immobilized on PVC and bentonite, respectively, when the COD loadings increased from 1.02 to 14.22 g; this showed an inhibition phenomenon in the three reactors studied. The values of the critical inhibitory substrate concentration (S*), theoretical kinetic constant without inhibition (KA) and the inhibition coefficient or inhibitory parameter for each reactor (n) were determined using the Levenspiel model. Copyright © 2004 Society of Chemical Industry
Journal of Chemical Technology & Biotechnology 02/2005; 80(3):241 - 250. · 2.17 Impact Factor
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ABSTRACT: A kinetic study of the anaerobic digestion process of two phases olive pomace (TPOP) was carried out in a laboratory-scale completely stirred tank reactor at mesophilic temperature (35 degrees C). The reactor was operated at influent substrate concentrations of 34.5 (substrate I), 81.1 (substrate II), 113.1 (substrate III), and 150.3 g COD/L (substrate IV). The hydraulic retention times (HRT) ranged between 8.3 and 40.0 days for the most diluted substrate (I) and between 10 and 50 days for the other three influent substrate concentrations used (substrates II-IV). The results obtained demonstrated that the rates of substrate uptake and methane production were correlated with the concentration of biodegradable total chemical oxygen demand (COD), through equations of the Michaelis-Menten type. A mass (COD) balance around the reactor allowed the methane yield coefficient and cell maintenance coefficient to be obtained, which gave values of 0.25 L CH(4)/g COD(t) and 0.25 days(-1), respectively. The first one was coincident to that obtained through experimental data of methane production and substrate consumption. The kinetic equations obtained and the proposed mass balance were used to simulate the anaerobic digestion process of TPOP and to obtain the theoretical COD of the reactor and methane production rates. The small deviations obtained (equal or lower than 10%) between the values calculated through the model and experimental ones suggest that the proposed model predicts the behavior of the reactor very accurately.
Journal of Agricultural and Food Chemistry 06/2003; 51(11):3390-5. · 2.82 Impact Factor
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ABSTRACT: A kinetic analysis of the anaerobic digestion process of wastewater derived from the production of protein isolates from extracted sunflower flour was carried out. The digestion was conducted in a laboratory-scale fluidized bed reactor with saponite (magnesium silicate) as support for the mediating bacteria at psychrophilic temperature (15-19 degrees C). Soluble chemical oxygen demand (COD(s)) removal efficiencies in the range of 95.9-69.0% were achieved in the reactor at organic loading rates (OLR) of between 0.57 and 2.49 g total COD (COD(t))/L d, hydraulic retention times (HRT) of between 20.0 and 4.5 days, and average feed total COD concentration of 11.3 g/L. The yield coefficient of methane production was 0.32 L of methane (at STP) per gram of COD(t) removed. The total volatile fatty acid (TVFA) levels and the TVFA/alkalinity ratio were lower than the suggested limits for digester failure for OLR and HRT up to 2.26 g COD(t)/L d and 5.0 days, respectively. The specific rate of substrate uptake, r (g COD(s)/g VSS d), correlated with the concentration of biodegradable substrate, S (g COD(s)/L), through an equation of the Michaelis-Menten type. The maximum substrate utilization rate, k, and the Michaelis constant, K(s)(), were found to be 0.125 g COD(s)/g VSS d and 124 mg COD(s)/L, respectively. This proposed model predicted the behavior of the reactor very accurately showing deviations lower than 10% between the experimental and theoretical values of substrate uptake rates. A mass (COD(t)) balance around the reactor allowed the COD equivalent of methane volume (W(CH)4) to be obtained, which gave a value of 2.89 g COD(t)/L CH(4), which was virtually coincident with the theoretical value of 2.86 g COD(t)/L CH(4).
Journal of Agricultural and Food Chemistry 08/2002; 50(16):4628-33. · 2.82 Impact Factor
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ABSTRACT: A laboratory-scale study was conducted on the aerobic degradation of two-phase olive mill effluents (TPOME) made up of the mixture of the washwaters derived from the initial cleansing of the olives and those obtained in the washing and purification of virgin olive oil. The process was carried out in a 1-l working volume stirred tank reactor operating in batch mode at room temperature (25 °C). The reactor was operated at influent substrate concentrations of 2.80 g COD/l (TPOME 25%), 5.45 g COD/l (TPOME 50%), 8.18 g COD/l (TPOME 75%) and 10.90 g COD/l (TPOME 100%). After five days of operation time, total and soluble COD removal efficiencies of 64.3% and 66.6% were achieved respectively for the most concentrated influent used (TPOME 100%). A simplified kinetic model for studying the hydrolysis of insoluble organic matter, oxidation of soluble substrate and biomass production was proposed on the basis of the experimental results obtained. The following kinetic constants with their standard deviations were obtained for the above stages in the case of the most concentrated influent used (TPOME 100%): k1 (kinetic constant for hydrolysis of suspended organic matter): 0.11 ± 0.01 l/(g VSS day); k2 (kinetic constant for total consumption of soluble substrate): 0.30 ± 0.02 l/(g VSS day); k3 (endogenous metabolism constant): 0.07 ± 0.01 per day). Finally, the biomass yield coefficient was found to be 0.30 g VSS/g CODremoved. The values of non-biodegradable total and soluble CODs obtained from the model were found to be 3 and 2 g/l, respectively. The kinetic constants obtained and the proposed equations were used to simulate the aerobic degradation process of TPOME and to obtain the theoretical values of non-soluble and soluble CODs and biomass concentration. The small deviations obtained (equal or lower than 10%) between the theoretical and experimental values suggest that the parameters obtained represent and predict the activity of the microorganisms involved in the overall aerobic degradation process of this wastewater.
Biochemical Engineering Journal. 30(3):308-315.
