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En el año 2015 apareció de forma masiva en las costas de Ceuta el alga parda Rugulopteryx okamurae (Dictyotales, Ochrophyta). Lo que provocó que en el año 2020 fuera considerada como una especie invasora por la Unión Europea. Desde entonces, el alga R. okamurae se ha expandido rápidamente a lo largo del Mediterráneo causando un impacto ambiental sin precedentes. Paralelamente, la búsqueda de tecnologías más sostenibles capaces de competir con los productos derivados de los combustibles fósiles aboga por el uso de biomasas de origen natural por su potencial para la producción energética y para la obtención de compuesto de alto valor. Entre estas biomasas, las macroalgas han destacado como biomasas de tercera generación. Desde la perspectiva de la economía circular, la digestión anaerobia (DA) es considerada un proceso altamente eficaz. La comunidad microbiana involucrada en el proceso convierte el sustrato en biogás (rico en metano) y en un efluente rico en nutrientes. Sin embargo, las macroalgas presentan algunos inconvenientes que no permiten una digestión eficiente: baja relación C/N y presencia de compuestos difícilmente degradables o inhibitorios. Esta Tesis propone y evalúa el aprovechamiento integral de la especie invasora R. okamurae. Inicialmente, se aplicaron pretratamientos térmicos y mecánicos, buscando la rotura de la pared celular del alga y la descomposición de compuestos difícilmente degradables, como la celulosa cristalina. El mayor rendimiento en metano fue obtenido tras la aplicación del pretratamiento térmico de 120 oC durante 45 min y tras el pretratamiento mecánico asistido con zeolita, sin observarse diferencias significativas entre ambos (240 - 250 NLCH4 kg-1 VS). Posteriormente, se evaluó el impacto del ciclo de vida de esta especie en el sistema de DA, pretratando la biomasa según los resultados anteriores. El mayor rendimiento en metano se obtuvo a partir del alga de arribazón fresco pretratada mecánicamente con zeolita (219 (15) NLCH4 kg-1, Although it was in 2002 in France when the brown seaweed Rugulopteryx okamurae (Dictyotales, Ochrophyta) was observed for the first time in the Mediterranean Sea, it wasn´t until 2015 at Ceuta when its drastic appearance was considered as an invasion of European concern (2020). Since then, R. okamurae has spread through the Mediterranean Sea and beyond extremely quick causing an unprecedented ecological impact. Additionally, global warming has drove the scientific efforts to look for greener technologies able to compete with fossil-fuel alike-products. In this context, natural biomasses are considered promising feedstocks for energy production and for added-value compound generation. Among these biomasses, macroalgae have drawn the attention over the last decade as a third-generation feedstock, reaching a global production of circa 24 million tons in the 2022 season. Within this circular and greener perspective, anaerobic digestion (AD) is known as a promising technique. The microbial community involved in the process degrades the substrate into a biogas (enriched in CH4) with energy value and into a nutrient-rich effluent with soil applications. However, macroalgae present some drawbacks that do not allow for an efficient AD performance: low C/N ratio and the presence of non-degradable compounds, which led to the inhibition of the AD process. A more comprehensive review of the specific scientific bibliography and the context and motivation of the present Thesis is presented in Chapter 1. In order to avoid the issues related to macroalgae as feedstock for the AD process, some alternatives have been proposed and evaluated in this Thesis. As a first start point, the algal biomass was subjected to conventional thermal pretreatments and a new developed mechanical pretreatment based on the use of zeolite during the milling process. These treatments are generally focused on the breakdown of the alga cell wall and the decomposition of, otherwise, non-easily biodegradable c

The Folin-Ciocalteu method can be considered to be the most widely used in laboratories around the world, to quantify the total polyphenols content. Many different variations found in this assay have been reported in the scientific literature. In this review, the full experimental conditions influencing the Folin-Ciocalteu assay have been comparatively assessed and discussed. Furthermore, few studies relating to the method validation have been evaluated according to the results of selectivity, linearity, precision, trueness, limit of determination, limit of quantification and robustness. In general, the results derived from the reviewed literature are widely variable according to both, the experimental factors selected and the performance parameters reported, making difficult the comparison of the overall results published.

The invasive alien seaweed Rugulopteryx okamurae (R.o.) has spread quickly through the Mediterranean Sea causing an unprecedented ecological impact. A solution integrated into a circular economy model is needed in order to curb the negative effects of its presence. Anaerobic digestion (AD) is proposed as a feasible process able to transform biomass into renewable energy. Nevertheless, in order to improve the methane yield and surpass the drawbacks associated with AD processes, this research proposes a thermal pretreatment and a new developed method where the macroalgae is mechanically pretreated with zeolite. Chemical and microstructure characterization of the algal biomass after pretreatments involved scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The highest methane yields of 240 (28) and 250 (20) NLCH4 kg−1 VSadded were obtained with the new mechanical pretreatment and the thermal pretreatment at 120 °C for 45 min without zeolite, achieving a 35 % improvement against the non-pretreated algae. A direct relationship between the crystallinity index of the samples and methane production was observed. The experimental data of methane production versus time were found to be in accordance with both first-order kinetic and Transference Function mathematical models.

The invasive alien seaweed Rugulopteryx okamurae (R.o.) has spread quickly through the Mediterranean Sea causing an unprecedented ecological impact. A solution integrated into a circular economy model is needed in order to curb the negative effects of its presence. Anaerobic digestion (AD) is proposed as a feasible process able to transform biomass into renewable energy. Nevertheless, in order to improve the methane yield and surpass the drawbacks associated with AD processes, this research proposes a thermal pretreatment and a new developed method where the macroalgae is mechanically pretreated with zeolite. Chemical and microstructure characterization of the algal biomass after pretreatments involved scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The highest methane yields of 240 (28) and 250 (20) NLCH4 kg-1 VSadded were obtained with the new mechanical pretreatment and the thermal pretreatment at 120 °C for 45 min without zeolite, achieving a 35 % improvement against the non-pretreated algae. A direct relationship between the crystallinity index of the samples and methane production was observed. The experimental data of methane production versus time were found to be in accordance with both first-order kinetic and Transference Function mathematical models.

Matrix components of a sample can affect the quantitative measurement of the target analytes. This singularity is named “matrix effects” and should be considered for method validation procedure. Two main strategies to overcome matrix effects were suggested in the scientific literature: reducing the presence of components responsible for the effects and compensating the influence of matrix effects in the calibration methodology. It has been recommended that the best option to surpass matrix effects at research level is to establish a systematic optimization by the combination of approaches. On the other hand, from the method validation regulatory viewpoint, the information contained in the different method validation guidelines about matrix effects was uncommon. In fact, only in 54% of the evaluated regulatory documents the term matrix effects was mentioned explicitly in their contents. In addition, in the rest of the guidance documents addressing matrix effects, the subject was typically considered only superficially.

Background Measurement of anti-SARS-CoV-2 RBD Ig G antibody response is very important to define the dynamics of immunization in vaccine COVID-19 recipients. Materials and methods Sera from four BNT162b2 vaccine recipients who erroneously received vaccine overdose were analyzed at different time-points. Results At 6 days the serum increase of antibodies was analogous for the three SARS-CoV-2 naïve recipients. At 14 days the antibody level increased and reached a peak, though showing a different pattern among the three recipients. At 21 days the serum antibody level started to decrease from its maximum value. The data for the previously infected recipient were in agreement with values found in COVID-19 positive receivers. Thus, the prime-dose of vaccine was enough to elicit a significant antibody response. Conclusions In spite of the overdosage, this study confirms the efficiency of the BNT162b vaccine in eliciting a sustained antibody response as heterologous boost-vaccine in previously Oxford/AstraZeneca vaccinated recipients, as well as, prime-vaccine in COVID-19 infected receivers. Importantly, the humoral immune response of recipients was not proportional to the vaccine overdose. Nonetheless, we cannot portray a univocal effect of vaccine overdose concerning anti-SARS-CoV-2 antibody response because the values found were highly heterogeneous.

Objectives The main purpose of this study was to evaluate the anti-SARS-CoV-2 RBD Ig G antibody response in BNT162b2 vaccine recipients who erroneously received vaccine overdose. Methods Measurement of antibody levels at different time-points was performed to define the dynamics of immunization after a wrongly vaccination schedule. Three recipients had no previous evidence of infection and received the first shot of Oxford/AstraZeneca before the Pfizer/BioNTech vaccine. Another patient, formerly infected by SARS-CoV-2, received one shot of BNT162b2 vaccine. Results At day 6 after the second vaccine dose the serum increase of anti-SARS-CoV-2 RBD Ig G antibodies was analogous for the three SARS-CoV-2 naïve recipients. At 14 days the antibody level increased and reached a peak, though displaying a different pattern among the three recipients. At 21 days the serum antibody level started to decrease from its maximum value. The data for the previously infected recipient were in agreement with values found in COVID-19 positive receivers. Thus, after the single prime-dose of vaccine, the elicited antibody response was similar to prime-boost vaccination in naïve recipients. Conclusions This study confirms the efficiency of the BNT162b vaccine in eliciting a sustained antibody response as heterologous boost-vaccine in previously Oxford/AstraZeneca vaccinated recipients, as well as, prime-vaccine in COVID-19 infected receivers. Importantly, the humoral immunity response of recipients was not proportional to the vaccine overdose. Nonetheless, we cannot portray a univocal effect of vaccine overdose concerning anti-SARS-CoV-2 antibody response because the values found especially in the three SARS-CoV-2 naïve subjects were highly heterogeneous.

This critical review paper will discuss the main analytical calibration models as well as the guidelines for their practical use. The main models used to fit a multiple-point calibration dataset are: 1) linear unweighted or ordinary least squares regression (OLSR); 2) quadratic unweighted least squares regression (QLSR); 3) linear weighted least squares regression (WLSR). Unfortunately, there is no standard procedure in analytical chemistry for objectively testing the goodness-of-fit of calibration models. Different proposals were reported in the literature. However, none is more commonly used, and probably not more controversial than R2. In this document, a three step simple calibration diagnosis has been proposed. It is based on a combination of different procedures such as graphical plots, statistical significance tests and numerical parameters. Experimental conditions and design of calibration procedures are very relevant for appropriate selection. Finally, some information on the choice of the different models will be reported in four case studies.

The main objective of method validation process is to prove that an analytical method is acceptable for its intended purpose. The necessity for laboratories to use fully validated methods is now universally accepted as a way to obtain reliable results. There are diverse documents for method validation including information about different performance parameters. The classical performance characteristics are accuracy, limit of detection, precision, recovery, robustness, ruggedness, selectivity, specificity and trueness. Unfortunately, contradictory information is normally present among the method validation documents used by laboratories. The inconsistency about the performance parameters can generate some degree of confusion in the complete method validation process. This manuscript addresses controversial and discrepant information, focusing specifically on several national and international method validation guidelines published by prominent organizations and institutions which serve as guidance to validate new analytical methods by practitioners working in different fields.

This paper is a compilation of some experimental results published in peer-reviewed articles dealing with predictive regression models between biochemical methane potential tests and different chemical parameters characterizing the organic content of biomass samples. Results reviewed were focused on laboratory measurements with the main objective of bringing together the existing experience to evaluate pitfalls and challenges that could be generalized for future research using this kind of substrates. Firstly, BMP test measurements were briefly described for experimental approaches according to different factors such as inoculum, physical and chemical experimental conditions, inoculum to substrate ratio and gas measurement systems. A lot of information necessary when reporting BMP studies was not included in the description of most articles. It is also unexpectedly the lack of positive control tests as a way to check the reliability of the experimental results obtained. As consequence, BMP test results from different laboratories are normally inconsistent and irreproducible. Secondly, chemical parameters analysed in experimental research works such as moisture/dry matter, total chemical oxygen demand, carbohydrates, lipids, proteins and lignin were also reported in a comparative way. In fact, 70% of analytical determinations were covered in some degree, but the presence of a correct reference description was only occasional. Finally, general regression models were summarized. However, the development of one overall model that applies to all kind of samples is difficult to achieve. In order to be reliable and widely applicable, predictive regression models for methane production of biomass samples should be based on accurate laboratory measurements.

Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. Although several norms and guidelines for BMP tests exist, inter-laboratory tests regularly show high variability of BMPs for the same substrate. A workshop was held in June 2015, in Leysin, Switzerland, with over 40 attendees from 30 laboratories around the world, to agree on common solutions to the conundrum of inconsistent BMP test results. This paper presents the consensus of the intense roundtable discussions and cross-comparison of methodologies used in respective laboratories. Compulsory elements for the validation of BMP results were defined. They include the minimal number of replicates, the request to carry out blank and positive control assays, a criterion for the test duration, details on BMP calculation, and last but not least criteria for rejection of the BMP tests. Finally, recommendations on items that strongly influence the outcome of BMP tests such as inoculum characteristics, substrate preparation, test setup, and data analysis are presented to increase the probability of obtaining validated and reproducible results.

Since linear calibration is mostly preferred for analytical determinations, linearity in the calibration range is an important performance characteristic of any instrumental analytical method. Linearity can be proved by applying several graphical and numerical approaches. The principal graphical criteria are visual inspection of the calibration plot, the residuals plot, and the response factors plot, also called sensitivity or linearity plot. All of them must include confidence limits in order to visualize linearity deviations. In this work, the graphical representation of percent relative errors of back-calculated concentrations against the concentration of the calibration standards is proposed as linearity criterion. This graph considers a confidence interval based on the expected recovery related to the concentration level according to AOAC approach. To illustrate it, four calibration examples covering different analytical techniques and calibration situations have been studied. The proposed %RE graph was useful in all examples, helping to highlight problems related to non-linear behavior such as points with high leverage and deviations from linearity at the extremes of the calibration range. By this way, a numerical decision limit which takes into account the concentration of calibration standards can be easily included as linearity criterion in the form of %RE=2·C. Accordingly, this %RE parameter is accurate for the decision-making related to linearity assessment according to the fitness-for-purpose approach.

Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced.

The analytical calibration of an instrumental method is very important, being considered as a key point in method validation. There are different validation guidelines; showing that analytical calibration process variety prevails in terms of nomenclature, methodology employed and acceptance criteria. Very common mistakes in the analytical calibration process are the use of correlation and/or determination coefficients as a test for linearity, the negligence in the heteroscedasticity of the experimental data and selection of appropriate weighting factor, misunderstanding about the regression through the origin and using zero-point calibration. Once the calibration function is established, their linearity can be confirmed by using different procedures such as graphical plots, statistical significance tests and numerical parameters. In particular, deviation from back-calculated concentrations expressed in the form of percentage of relative error (%RE) can be considered very useful for unambiguous linearity evaluation. Some case studies were included to explain the linearity assessment from a practical viewpoint.

The performance parameters of volatile fatty acids (VFAs) measurements were assessed for the first time by a multi-laboratory validation study among 13 laboratories. Two chromatographic techniques (GC and HPLC) and two quantification methods such as external and internal standard (ESTD/ISTD) were combined in three different methodologies GC/ESTD, HPLC/ESTD and GC/ISTD. Linearity evaluation of the calibration functions in a wide concentration range (10–1000 mg/L) was carried out using different statistical parameters for the goodness of fit. Both chromatographic techniques were considered similarly accurate. The use of GC/ISTD, despite showing similar analytical performance to the other methodologies, can be considered useful for the harmonization of VFAs analytical methodology taking into account the normalization of slope values used for the calculation of VFAs concentrations. Acceptance criteria for VFAs performance parameters of the multi-laboratory validation study should be established as follows: (1) instrument precision (RSDINST ≤ 1.5%); (2) linearity (R2 ≥ 0.998; RSDSENSITIVITY ≤ 4%; REMAX ≤ 8%; REAVER ≤ 3%); (3) precision (RSD ≤ 1.5%); (4) trueness (recovery of 97–103%); (5) LOD (≤3 mg/L); and (6) LOQ (10 mg/L).

En el proceso de extracción de aceite de la harina de girasol se generan residuos sólidos caracterizados por su elevado contenido en proteína y en compuestos lignocelulosicos. Su elevada producción en España (4-5 millones de toneladas/año) genera un importante problema medioambiental. En el tratamiento anaerobio de estos residuos se obtienen bajos coeficientes de rendimiento en metano y porcentajes de degradación de materia orgánica, observándose un claro efecto inhibitorio y una alta inestabilidad cuando se opera con velocidades de carga orgánica (VCO) mayores o iguales a 3 g SV/L•día. La baja velocidad de hidrólisis de la celulosa debido a su estructura cristalina, la asociación de la celulosa y hemicelulosa con la lignina y la baja actividad de las celulasas presentes en los digestores anaerobios son los principales factores que influyen en la lenta degradación anaerobia de estos residuos. Estudios previos han demostrado que la hidrólisis de la fracción lignocelulósica es claramente la etapa limitante de la velocidad del proceso de digestión anaerobia de este tipo de sustrato. Estos factores determinan la necesidad de utilizar elevados tiempos de retención hidráulicos (25-30 días) y son los responsables de la baja producción de biogás y pequeños coeficientes de rendimiento en metano observados en la digestión anaerobia de éste y de otros residuos agro-industriales. Estudios recientes han puesto de manifiesto que distintos tipos de pretratamientos de tipo térmico, químico, termoquímico, mecánico o con ultrasonidos incrementan la biodegradabilidad anaerobia, el porcentaje de sólidos orgánicos eliminados y en definitiva la producción de biogás y metano en el proceso de digestión anaerobia de algunos residuos agro-industriales, todos ellos caracterizados por su elevado contenido en compuestos lignocelulósicos. El pretratamiento de estos residuos con estructura compleja debida al entramado lignocelulósico, podría permitir hacer viable y optimizar el proceso de digesti

Anaerobic digestion is considered a competitive source for the production of renewable energy as far as efficiency and cost are concerned. To evaluate the anaerobic biodegradability of an organic substrate such as feedstocks, a test known as biochemical methane potential (BMP) has been commonly used. Current worldwide interest in using different organic substrates for anaerobic bioconversion is growing but there is a lack of clear references and comparability as a result of multiple factors that affect BMP determination. Several batch methods have been used to determine the methane potential. However, these technical approaches vary significantly from one reported method to the next another. In this review, the research works on the influence of different parameters of BMP determination have been discussed for critical and comparative evaluation. In addition, the extensive literature previously published dealing with BMP assays has been compiled and summarized focusing on two main subjects: firstly, methane yields of substrates, and secondly, the description of the various experimental procedures used to achieve the reported data. © 2011 Elsevier Ltd. All rights reserved.

Biochemical methane potential (BMP) assays of sunfloweroilcake (SuOC) were carried out to research the effect of different particlesizes and their chemicalcomposition on methane yields and kinetics. Particlesize ranges of (1) 0.355–0.55 mm, (2) 0.710–1.0 mm and (3) 1.4–2.0 mm in diameter were evaluated. The highest methane yield 213 ± 8 mL CH4 g−1 VSadded was obtained for the largest particlesize analyzed (3), against 186 ± 6 mL CH4 g−1 VSadded obtained for particles 1 and 2. This may be attributed to the different lignocellulose compositions of the various particlesize ranges studied and to organic matter removals (47.2% for 3, against ∼41.5% for 1 and 2). The evolution of propionic acid concentration was found to be fundamental for explaining the lowest rate of biogas production for the smallest (1) particlesize studied, with a specific rate constant k of 0.45 ± 0.02 d−1, while values of 0.61 ± 0.02 d−1 and 0.50 ± 0.01 d−1 were obtained for particles 2 and 3, respectively.

Background: This paper describes results obtained for different participating research groups in an interlaboratory study related to biochemical methane potential (BMP). In this research work, all experimental conditions influencing the test such as inoculum, substrate characteristics and experimental conditions were investigated. The study was performed using four substrates: three positive control substrates (starch, cellulose and gelatine), and one raw biomass material (mung bean) at two different inoculum to substrate ratios (ISR). Results: The average methane yields for starch, cellulose, gelatine and mung bean at ISR of 2 and 1 were 350 ± 33, 350 ± 29, 380 ± 42, 370 ± 36 and 370 ± 35 mL CH4 g-1 VSadded, respectively. The percentages of biotransformation of these substrates into methane were 85 ± 8, 85 ± 7, 88 ± 9, 85 ± 8 and 85 ± 8%, respectively. On the other hand, the first-order rate constants obtained from the experimental data were 0.24 ± 0.14, 0.23 ± 0.15, 0.27 ± 0.13, 0.31 ± 0.17 and 0.23 ± 0.13 d-1, respectively. Conclusion: The influence of inocula and experimental factors was nearly insignificant with respect to the extents of the anaerobic biodegradation, while the rates differed significantly according to the experimental approaches. © 2011 Society of Chemical Industry.

The effect of the hydraulic retention time and the sulphate-total COD ratio on the performance of an anaerobic biological process applied to acid mine drainage water (AMD) was evaluated using cheese whey as a carbon source. Laboratoryscale fixed bed bioreactors operating at 25 ± 2 ºC were used in the experiments. Maximum sulphate reduction and hydrogen sulphide production were achieved at a hydraulic retention time of 8 days and at a sulphate-total COD ratio of 0.5. Under these conditions, the sulphate removal was found to be 68.1% while the hydrogen sulphide production was 0.27 L/day. At the same time, the total COD removal obtained was 55.4%

The effect of the hydraulic retention time and the sulphate-total COD ratio on the performance of an anaerobic biological process applied to acid mine drainage water (AMD) was evaluated using cheese whey as a carbon source. Laboratoryscale fixed bed bioreactors operating at 25 ± 2 ºC were used in the experiments. Maximum sulphate reduction and hydrogen sulphide production were achieved at a hydraulic retention time of 8 days and at a sulphate-total COD ratio of 0.5. Under these conditions, the sulphate removal was found to be 68.1% while the hydrogen sulphide production was 0.27 L/day. At the same time, the total COD removal obtained was 55.4%.

Chemical oxygen demand (COD) is a critical analytical parameter in waste and wastewater treatment, more specifically in anaerobic digestion, although little is known about the quality of measuring COD of anaerobic digestion samples. Proficiency testing (PT) is a powerful tool that can be used to test the performance achievable in the participants’ laboratories, so we carried out a second PT of COD determination in samples considered “difficult” to analyze (i.e. solid samples and liquid samples with high concentrations of suspended solids). The results obtained (based on acceptable z-score values) may be considered satisfactory. When compared with the results of a previous similar scheme, the overall performance improved by around 30%, again demonstrating that analytical performance can be improved by regular participation in PT.

In 2008, the first Proficiency Testing Scheme of Chemical Oxygen Demand (1stCOD-PTADG) was conducted to assess the results obtained for different research groups whose field work is mainly anaerobic digestion. This study was performed using four samples, two solid samples as raw materials and two solid samples to prepare high concentration suspended solid solutions. Invitations were sent to a large number of laboratories, mainly to anaerobic digestion research groups. Finally, thirty labs from sixteen countries agreed to participate, but for different reasons four participants could not send any data. In total, twenty-six results were reported to the COD-PT coordinator. This study showed the importance of continuous participation in proficiency testing (PT) schemes in order to compare the results obtained. Taking into account the lack of a general standard method and high quality certified reference materials (CRMs), the traceability of COD determination is not currently easy to check. In addition, the spread of participants’ results obtained was high and pointed to the advisability of using consensus values due to their unreliability. Therefore, the theoretical oxygen demand (ThOD) values were considered as assigned values for all the samples analysed. On the other hand, in this PT the established standard deviation (ESD) has been determined by the Horwitz modified function. Participants of this 1stCOD-PTADG were asked to give a short report on the analytical method used. Although all the participants used potassium dichromate as their oxidant reagent, their experimental procedures were very different. With the purpose of comparing the results obtained, the different experimental conditions used were classified into five methods, corresponding to two main categories, open and closed reflux. The performance of laboratories was expressed by the z-score, whose value is considered satisfactory when z-score ≤±2. The overall analytical data evaluation showed that 64% of

The adsorption of methylene blue (MB) on three commercial granular activated carbons (GACs), 12 × 40 mesh size, namely Filtrasorb 400, Norit and Picacarb has been researched. A comparative study of adsorptive capacity using the proposed single-point test and the traditional multi-point isotherm test was carried out. For the single-point test, the influence of some parameters such as MB/GACs mass ratio and contact time were evaluated. For this test the adsorptive capacities of the three GACs studied were 319 ± 14, 280 ± 7 and 260 ± 6 mg g−1 for Filtrasorb 400, Norit and Picacarb, respectively. For multi-point isotherm adsorption test the Langmuir model was used. The parameters involved were obtained by linear and non-linear regression methods. The maximum adsorptive capacity values obtained for both methods were similar and statistically not different than those obtained with the single-point tests. This experimental work also aimed at establishing a relationship between the adsorbent particle size and the adsorptive capacity which could be used complementarily to evaluate the quality of GACs as adsorbents. For a mean particle diameter of 1 mm and after 24 h of contact time the adsorptive capacity values were 255 ± 7, 222 ± 7 and 160 ± 7 mg g−1 for Filtrasorb 400, Norit and Picacarb, respectively.

A study of the anaerobic digestion of the solid waste generated in the extraction process of sunflower oil (sunflower oil cake, SuOC) was conducted at mesophilic temperature (35 °C) in batch mode. A laboratory-scale multi-reactor system was used to compare the volatile solids (VS) degradation and methane production (G) at inoculum–substrate ratios (ISRs) of 3.0, 2.0, 1.5, 1.0, 0.8 and 0.5 (expressed as VS basis). All tests were carried out against controls of inoculum without substrate. The stability and progress of the reaction from solid substrate to methane as an end product was monitored by measuring the pH, the soluble chemical oxygen demand, and the total volatile fatty acids-total alkalinity (TVFA/TA) ratio. The results obtained demonstrated that in the ISR range from 3.0 to 0.8, the pH ranged from 7.1 to 7.6 and this parameter was always stable during the anaerobic digestion process. In addition, within the above ISR range the TVFA/TA ratios were always lower than the failure limit values (0.3–0.4), which demonstrated the high stability of the anaerobic digestion process of this substrate at mesophilic temperature. Two kinetic models for substrate (VS) degradation and methane production were proposed and evaluated. The apparent kinetic constants for volatile solids degradation (K1) and methane production (K2) decreased from 0.54 ± 0.09 to 0.32 ± 0.03 d−1 and from 0.36 ± 0.04 to 0.16 ± 0.03 d−1, respectively, when the ISR decreased from 3.0 to 0.5, showing the occurrence of an inhibition phenomenon by substrate concentration. The kinetic equations obtained were used to simulate the anaerobic digestion process of SuOC and to obtain the theoretical VS and methane production values. The low deviations obtained (equal to or lower than 10%) between the theoretical and experimental values suggest that the proposed models predict the behaviour of the reactors very accurately.

Four alternatives (runs A, B, C and D) for heavy metals removal (Fe, Cu, Zn and Al) from acid mine drainage water (AMDW) produced in the mining areas of the Huelva Province, Spain, were evaluated. In run A, the anaerobic effluent from the treatment of acid mine drainage water (cheese whey added as a source of carbon) was mixed with the raw AMDW. The pH increased to 3.5 with the addition of KOH. In run B, biogas with around 30% of hydrogen sulphide obtained in the anaerobic reactor was sparged to the mixture obtained in run A, but in this case at a pH of 5.5. In run C, the pH of the raw AMDW was increased to 3.5 by the addition of KOH solution. Finally, in run D, the pH of the raw AMDW was increased to 5.5 by the addition of KOH solution and further biogas was sparged under the same conditions as in run A. It was found that heavy metal removal was a function of pH. At a pH of 3.5 most of the iron was removed while Zn and Cu were partially removed. At a pH of 5.5 the removal of all metals increased considerably. The best results were obtained in run B where the percentages of removal of Fe, Cu, Zn and Al achieved values of 91.3, 96.1, 79.0 and 99.0%, respectively. According to the experimental results obtained tentative schemas of the flow diagram of the processes were proposed.

The influence of the hydraulic retention time (HRT) and organic loading rate (OLR) on the performance of the hydrolytic–acidogenic step of a two-stage anaerobic digestion process of sunflower oil cake (SuOC) were assessed. The experiments were performed in laboratory-scale completely stirred tank reactors at mesophilic (35 °C) temperature. Six OLR (ranging from 4 to 9 g VS L−1 d−1) for four HRTs (8, 10, 12 and 15 days) were tested to check the effect of each operational variable. Based on the results obtained, it can be concluded that the hydrolysis yields obtained for all HRTs and OLRs assayed were in the range of 20.5–30.1%. In addition, the acidification degree of the substrate was mainly influenced by the OLR but not by the HRTs, the highest value (83.8%) being achieved for an HRT of 10 days and an OLR of 6 g VS L−1 d−1.

The effect of the hydraulic retention time (HRT) on the performance of two up-flow anaerobic fixed bed digesters (UFAFBDs) packed with waste tire rubber (D1) and waste tire rubber and zeolite (D2) as micro-organism immobilization supports was studied. It was found that a first-order kinetic model described well the experimental results obtained. The kinetic constants for COD, BOD5, total solids (TS) and volatile solids (VS) removal were determined to be higher in digester D2 than in digester D1 or control. Specifically, they were 0.28 ± 0.01, 0.32 ± 0.02, 0.16 ± 0.01 and 0.24 ± 0.01 d− 1 respectively for D1 and 0.33 ± 0.02, 0.40 ± 0.02, 0.21 ± 0.01 and 0.28 ± 0.01 d− 1 respectively for D2. This was significant at the 95% confidence level. In addition, the first-order model was also adequate for assessing the effect of the HRT on the removal efficiency and methane production. Maximum methane yield and the first-order constant for methane production were determined and the results obtained were comparable with those obtained by other authors but operating at higher HRTs. Maximum methane yields and the kinetic constant for methane production were 11.1% and 29.4% higher in digester D2 than in D1.

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, 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, obt

A study of the performance and microbial communities of a continuous stirred tank reactor (CSTR) treating two-phases olive mill solid wastes (OMSW) was carried out at laboratory-scale. The reactor operated at a mesophilic temperature (35 °C) and an influent substrate concentration of 162 g total chemical oxygen demand (COD) L−1 and 126 g volatile solids (VS) L−1. The data analyzed in this work corresponded to a range of organic loading rates (OLR) of between 0.75 and 3.00 g COD L−1 d−1, getting removal efficiencies in the range of 97.0–95.6%. Methane production rate increased from 0.164 to 0.659 L CH4 Lreactor−1 d−1 when the OLR increased within the tested range. Methane yield coefficients were 0.225 L CH4 g−1 COD removed and 0.290 L CH4 g−1 VS removed and were virtually independent of the OLR applied. A molecular characterization of the microbial communities involved in the process was also accomplished. Molecular identification of microbial species was performed by PCR amplification of 16S ribosomal RNA genes, denaturing gradient gel electrophoresis (DGGE), cloning and sequencing. Among the predominant microorganisms in the bioreactor, the Firmicutes (mainly represented by Clostridiales) were the most abundant group, followed by the Chloroflexi and the Gamma-Proteobacteria (Pseudomonas species as the major representative). Other bacterial groups detected in the bioreactor were the Actinobacteria, Bacteroidetes and Deferribacteres. Among the Archaea, the methanogen Methanosaeta concilii was the most representative species.

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, 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, obte