Harmonization of VFAs measurement by GC: something more than R2 to evaluate the calibration function

Anaerobic digestion is sensitive to many environmental factors requiring a robust control of this process. One of the analytical measurements considered as key parameter is the volatile fatty acids (VFAs) content. Total amount of volatile acids (TVFA) to control the relative changes over time has been suggested as a useful tool. However, TVFA does not provide sufficient information to reveal the overall reactor performance, and individual components have been considered of particular interest. Although some attempts have been described as on-line measurements for individual VFAs, normally they are determined by off-line chromatographic techniques (GC and HPLC). A previous interlaboratory study showed the lack of harmonization in the analytical methodologies dealing to individual VFAs, and giving an overall analytical performance rather poor. One of the reasons to justify these results was the inappropriate calibration procedures. It is widely used to check the linearity of the calibration curves based on the correlation and determination coefficients. However, these statistical parameters are erroneously interpreted. The objective of this interlaboratory study was to achieve the harmonization of results. By this way, the use of internal standard methodology (ISTD) should be useful to obtain accurate calibration functions. In addition, five different statistical parameters such as lack of fit test, residual standard deviation, relative standard deviation of the slope, relative standard deviation of the sensitivity and relative error were proposed to evaluate the linearity of calibration curves. Of these, lack of fit was unable to detect appropriately the linearity mainly due to its sensitivity to the precision of analytical results. The rest of statistical parameters reported could be considered as starting point for comparative purposes, being useful as acceptance criteria. The principal advantage of the GC/ISTD analytical methodology was the normalization of the slopes obtained by the participating laboratories, being very helpful to the harmonization of results.Peer Reviewe

Potentialités d’un procédé combinant ozone et biodégradation: application au traitement de la DCO dure et colorée d’un effluent d’origine agro-alimentaire

Soutenue le 18 décembre Diplôme : Dr. d'UniversitéThis thesis aimed to develop a process combining ozonation and biodegradation, applied to a biorefractory wastewater containing melanoidins from molasses fermentation industry. This study also focused on the evaluation of solid catalysts containing noble metals supported on activated carbon or alumina, in the form of powders, pellets or balls, to improve performance of the phsyico-chemical pretreatment. The biorefractory COD in the effluent is 2 g.L-1, with a characteristic brown color. Ozonation runs without catalyst revealed an optimal ozone dose. For ozonation, the color could be completely removed while a residual COD was slowly oxidized for higher ozone doses. Combination of semi-continuous ozonation, at the optimal dose, with aerobic, anaerobic and anoxic biodegradations indicated 35% biodegradable COD after ozonation. The catalytic ozonation studies conducted in batch and in semi-continuous conditions quantified the performance of the catalysts, depending on the nature of both the support and the metal supported, at different concentrations. These performances were directly related to the COD adsorption on solid catalysts. Efficacy depended on both the catalyst properties and the experimental conditions, such as pH and alkalinity. The catalysts potential for the conversion of biorefractory COD into biodegradable one confirmed the need for the definition of an optimal dose for both catalyst and ozone related to the corresponding biodegradability.Cette thèse a pour objectif le développement d'un procédé combinant ozonation et biodégradation, appliqué à un effluent bioréfractaire issu de l'industrie de fermentation des mélasses contenant des mélanoïdines. Cette étude a également porté sur l'évaluation de catalyseurs solides, contenant des métaux nobles déposés sur charbon actif ou alumine, sous forme de poudres, de grains ou de billes, permettant d'améliorer les performances du prétraitement physico-chimique. La DCO dure de l'effluent s'élève à 2 g.L-1, de couleur brune caractéristique. Des essais d'ozonation, sans catalyseur, ont permis d'identifier une dose d'ozone optimale. Par ozonation, la couleur peut être complètement éliminée tandis qu'une fraction résiduelle de DCO est lentement oxydée pour des doses d'ozone élevées. Des essais en semi-continu combinant ozonation à la dose optimale et biodégradation aérobie, anaérobie et anoxie ont indiqué que la fraction biodégradable après ozonation s'élève à 35%. Les essais d'ozonation catalytique conduits en batch ainsi qu'en semi-continu ont permis d'évaluer les performances des catalyseurs, en fonction de la nature du support et du métal déposé, aux différentes concentrations. Ces performances sont directement liées aux phénomènes d'adsorption de la DCO sur les catalyseurs solides. L'efficacité est dépendante de la nature du catalyseur et des conditions de mise en œuvre, telles que le pH et l'alcalinité. Les résultats concernant les performances des catalyseurs pour convertir la DCO dure en DCO biodégradable confirment la nécessité de définir une dose optimale de catalyseur et d'ozone en relation avec la biodégradabilité correspondante

Etude agronomique d'une parcelle conduite en maraichage intensif

* INRA URD, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9 Diffusion du document : INRA URD, Domaine St Paul, Site Agroparc, 84914 Avignon cedex

Potentialités d un procédé combinant ozone et biodégradation (application au traitement de la DCO dure et colorée d un effluent d origine agro-alimentaire)

Cette thèse a pour objectif le développement d'un procédé combinant ozonation et biodégradation, appliqué à un effluent bioréfractaire issu de l'industrie de fermentation des mélasses contenant des mélanoïdines. Cette étude a également porté sur l'évaluation de catalyseurs solides, contenant des métaux nobles déposés sur charbon actif ou alumine, sous forme de poudres, de grains ou de billes, permettant d'améliorer les performances du prétraitement physico-chimique. La DCO dure de l'effluent s'élève à 2 g.L-1, de couleur brune caractéristique. Des essais d'ozonation, sans catalyseur, ont permis d'identifier une dose d'ozone optimale. Par ozonation, la couleur peut être complètement éliminée tandis qu'une fraction résiduelle de DCO est lentement oxydée pour des doses d'ozone élevées. Des essais en semi-continu combinant ozonation à la dose optimale et biodégradation aérobie, anaérobie et anoxie ont indiqué que la fraction biodégradable après ozonation s'élève à 35%. Les essais d'ozonation catalytique conduits en batch ainsi qu'en semi-continu ont permis d'évaluer les performances des catalyseurs, en fonction de la nature du support et du métal déposé, aux différentes concentrations. Ces performances sont directement liées aux phénomènes d'adsorption de la DCO sur les catalyseurs solides. L'efficacité est dépendante de la nature du catalyseur et des conditions de mise en œuvre, telles que le pH et l'alcalinité. Les résultats concernant les performances des catalyseurs pour convertir la DCO dure en DCO biodégradable confirment la nécessité de définir une dose optimale de catalyseur et d'ozone en relation avec la biodégradabilité correspondante.This thesis aims to develop a process combining ozonation and biodegradation, applied to an biorefractory wastewater containing melanoidins from molasses fermentation industry. This study also focused on the evaluation of solid catalysts containing noble metals deposited on activated carbon or alumina, in the form of powders, pellets or balls, in order to improve performance of the phsyico-chemical pretreatment. The biorefractory COD contained in the effluent is 2 g.L-1, with a characteristic brown color. Ozonation tests without catalyst, have identified an optimal ozone dose. For ozonation, the color can be completely removed while a residual COD is slowly oxidized for high ozone doses. Combination of semi-continuous ozonation, at the optimal dose, with aerobic, anaerobic and anoxic biodegradations indicated 35% biodegradable COD after ozonation. The catalytic ozonation study conducted in batch and in semi-continuous conditions have evaluated the performance of catalysts, depending on the nature of both the support and the metal deposited, at different concentrations. These performances are directly related to the COD adsorption on solid catalysts. Efficacy depends on both the catalyst properties and the experimental conditions, such as pH and alkalinity. The catalysts potential for the conversion of biorefractory COD into biodegradable one confirm the need for the definition of an optimal dose of catalyst and ozone related to the corresponding biodegradability.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

High-Rate Anaerobic Digestion of Waste Activated Sludge by Integration of Electro-Fenton Process

Anaerobic digestion (AD), being the most effective treatment method of waste activated sludge (WAS), allows for safe disposal. The present study deals with the electro-Fenton (EF) pretreatment for enhancing the WAS biogas potential with low-cost iron electrodes. The effect of pretreatment on the physicochemical characteristics of sludge was assessed. Following EF pretreatment, the pH, conductivity, soluble chemical oxygen demand (SCOD), and volatile fatty acids (VFA) increased to 7.5, 13.72 mS/cm, 4.1 g/L, and 925 mg/L, respectively. Capillary suction time (CST) analysis highlighted the dewaterability effect of EF on WAS, as demonstrated by the decrease in CST from 429 to 180 s following 30 min of pretreatment. Batch digestion assays presented an increase in the biogas yield to 0.135 L/g volatile solids (VS) after 60 min of EF pretreatment in comparison to raw sludge (0.08 L/g VS). Production of biogas was also found to improve during semi-continuous fermentation of EF-pretreated sludge conducted in a lab-scale reactor. In comparison to raw sludge, EF-pretreated sludge produced the highest biogas yield (0.81 L biogas/g VS) with a high COD removal rate, reaching 96.6% at an organic loading rate (OLR) of 2.5 g VS/L. d. Results revealed that the EF process could be an effective WAS disintegration method with maximum recovery of bioenergy during A

Co-digestion de déchets solides : Caractérisation de la fraction liquide des digestats après séparation liquide/solide : Focus sur la teneur en matière organique résiduelle et sa biodégradabilité

Co-digestion de déchets solides : Caractérisation de la fraction liquide des digestats après séparation liquide/solide. Focus sur la teneur en matière organique résiduelle et sa biodégradabilité. Journées Recherche et Industrie Biogaz méthanisatio

Performance of UASB reactor treating waste activated sludge: Effect of electro-chemical disintegration on the anaerobic microbial population structure and abundance

The electro-Fenton (EF) disintegration using iron electrodes was performed for the pretreatment of waste activated sludge (WAS). The effect of this electro-chemical pretreatment on anaerobic digestion (AD) performance and microbial population structure was studied. An improvement of biodegradability and bioaccessibility of organic matter was demonstrated. AD of pretreated WAS in an up-flow anaerobic sludge blanket reactor (UASB) resulted to an increase of biogas production by 60 % compared to control reactor without disintegration. PCR-DGGE and real-time qPCR analyses showed that the high abundance of bacteria and the coexistence of Coprothermobacter in the UASB digestate fed with disintegrated sample established a stable bacterial association which is in line with the AD performance. Besides, the increased number of methanogens along the process allowed the improvement of methane production in comparison to control reactor

Methane potential of waste activated sludge and fatty residues: impact of codigestion and alkaline pretreatments

The aim of this study was to maximise methane production from waste activated sludge (WAS) originating from extended aeration process and presenting a low methane potential (190 mL CH4.g-1 OM). WAS co-digestion with fatty residues (FR, 560 mL CH4.g-1 OM) produced during pretreatments of the effluents from wastewater treatment plants in the Lille area and fatty wastewaters (FW, around 700 mL CH4.g-1 OM) collected from restaurants was assessed by batch experiments. Moreover saponification/alkali pretreatments improved kinetics of anaerobic digestion but had a low impact on methane potential (+ 6-7%) of the mixed waste composed of 66.6% of FW, 33.3% of WAS and 0.1% of FR. As results did not depend on pH ranging from 8 to 10 (addition of 0.12 to 0.21 gKOH gOM-1 ) nor temperature ranging from 80 to 120 °C, the least severe studied pretreatment conditions (80°C and pH=8) may be selected for further studies on continuous anaerobic reactors