29 research outputs found
Suivi physico-chimique, microbiologique et écotoxicologique du compostage de boues de STEP mélangées à des déchets de palmier : validation de nouveaux indices de maturité
Le traitement de boues de station d'Ă©puration (Boues activĂ©es de Marrakech) en mĂ©lange avec dĂ©chets verts (Palmier dattier) selon deux mĂ©langes dont les proportions : A (1/3 Boues + 2/3 DĂ©chets de palmier) et B (1/2 Boues + 1/2 DĂ©chets de palmier), a Ă©tĂ© effectuĂ© par la filiĂšre du compostage, pendant six mois. Au cours du co-compostage, lâintense activitĂ© microbienne sâest traduite par une augmentation de tempĂ©rature (autour 65 C°) au cours des premiĂšres semaines (phase thermophile) et un taux de dĂ©composition final de lâordre de 40%. AprĂšs six mois de co-compostage, le compost final est caractĂ©risĂ© par un rapport C/N voisin de 10, un rapport de NH4+/NO3- < 1, un pH autour de la neutralitĂ© signe de maturitĂ© des composts. Lâanalyse FTIR a montrĂ© une diminution de l'absorbance des bandes aliphatiques et l'augmentation de la structure de bandes d'absorbance aromatiques reflĂštent l'Ă©tat d'avancement du processus d'humification. Le taux dâabattement des lipides totaux est de lâordre de 43%. Les esters mĂ©thyliques dâacide gras (FAMEs) des Gram-positif (i,C15 :0) ont augmentĂ© durant la phase thermophile. Les FAMEs dâorigine non spĂ©cifique (C6 :0, C14 :0) ont connu une intense diminution, les FAMEs de bactĂ©ries non spĂ©cifiques reprĂ©sentent une grande teneur durant la phase thermophile. Lâindice CPI a augmentĂ© Ă la fin du co-compostage indiquant lâenrichissement du compost en FAMEs dâorigine vĂ©gĂ©tale. Les principaux composĂ©s ligneux identifiĂ©s, au cours du co-compostage, par Py-GC-MS, sont classĂ©s en deux groupes. Le premier est constituĂ© de 7 composĂ©s dont la teneur diminue au cours du co-compostage, parmi lesquels : ToluĂšne, 2,4-dimĂ©thylbenzĂšne, Ă©thylbenzĂšne, StyrĂšne, 1-Ă©thyl-2-mĂ©thylbenzĂšne, 4-mĂ©thylphĂ©nol et 2-mĂ©thylnaphthalĂšne. Le deuxiĂšme groupe est constituĂ© de 4 composĂ©s qui augmentent au cours du co-compostage : phĂ©nol, benzofuran, Ă©thylmĂ©thoxyphĂ©nol et dimĂ©thoxyphĂ©nol. Les principaux stĂ©roĂŻdes identifiĂ©s sont les C27-C29 sterĂšnes, stanols, 5ÎČ-cholesta-3-one, cholesta-3,5-diĂšne et 2 thiostĂ©ranes. A lâexception des thiosteranes et quelques composĂ©s de C27-C29 cholestenes la concentration relative des stĂ©roides diminue au cours du processus suit Ă leur attaque microbien. Lâabattement total de la teneur des stĂ©roĂŻdes est corrĂ©lĂ© positivement avec les indicateurs de maturitĂ© du compost (C/N et NH4+/NO3-) ce qui ouvre la voie Ă une Ă©ventuelle utilisation des stĂ©roĂŻdes comme indicateur de dĂ©pollution et de maturitĂ© de compost. 12 isolats dâactinomycĂštes ayant une activitĂ© antimicrobienne vis-Ă -vis dâun large spectre des germes pathogĂšnes ont Ă©tĂ© isolĂ©s sur le milieu sĂ©lectif CTEA. Le degrĂ© dâhygiĂ©nisation est confirmĂ© par la diminution de la concentration des coliformes fĂ©caux et totaux, et lâabattement des Ćufs dâhelminthes identifiĂ©s (Ascaris sp., Capillaria sp., et Trichuris sp.) vers la fin du co-compostage. La phytotoxicitĂ©, dĂ©terminĂ©e par lâeffet des extraits hydrosolubles Ă diffĂ©rents stades de co-compostage sur la germination et la croissance des radicules (Navet, Cresson, Laitue, Luzerne), a diminuĂ© et lâindice de germination dĂ©passe 100%, aprĂšs six mois de co-compostage. La gĂ©notoxicitĂ© du chrome hexavalent (Cr(VI)) du substrat de co-compostage est corrĂ©lĂ©e positivement avec la frĂ©quence des micronoyaux (MN). AprĂšs six mois de co-compostage le taux des MN diminue avec un taux dâabattement de 70,4% et 77,2% avec lâabattement de la concentration du Cr(VI) avec 58 et 58,6% respectivement pour le mĂ©lange A et B. Ceci ouvrira la voie dâutilisation de cet indice comme un indice de maturitĂ© des composts. La diminution de la phytotoxicitĂ© et la gĂ©notoxictĂ© au cours du co-compostage confirme lâĂ©tat de stabilisation et de la maturitĂ© des co-composts, ce qui pemettra lâĂ©pandage de ces composts en tant quâamendement organique des sols sans risque de contamination du systĂšme sol-plante. ABSTRACT : The co-composting of activated sludge and lignocellulose waste (palm tree waste) was monitored to study the behaviour of two mixtures, referred to as A (1/3 sludge + 2/3 palm waste) and B (1/2 sludge + 1/2 waste palm) for 6 months. The biotransformation was evaluated by physicochemical and spectroscopic analyses. The thermophilic phase is characterized by a rise in temperature, which peaked at 65°C. This is the result of intense microbial activities. The final composts exhibited a higher degree of decomposition than the controls as shown by a decomposition rate of about 40%, decrease of C/N ratio to around 10 and NH4 +/NO3 - ratio below 1. The decrease of aliphatic absorbance bands and the increase of aromatic absorbance bands follow the progress of the humification process. Total extractable lipid was decreased by 43%. The fatty acid methyl esters (FAMEs) from Gram-positive bacteria (i, C15: 0) increased during the thermophilic phase. FAMEs from non-spĂ©cific origin (C6 :0, C14 :0) exhibited a decrease toward the end of co-compostin, linear FAMEs from non-specific bacteria underwent a decrease during co-composting. The CPI index thus increased at the end of the composting process, indicating that the final product was proportionally richer in fatty acids of plant origin. Two lignin groups were distinguished by Py-GC-MS. Group 1 contained toluene, 2,4-dimethylbenzene, ethylbenzene, styrene, 1-ethyl-2-methylbenzene, 4-methylphenol and 2-methylnaphthalene; their relative proportions decreased during co-composting. A second group of 4 components showed concentrations that increased with co-composting time: phenol, benzofuran, ethylmethoxyphenol and dimethoxyphenol. The main steroids identified were C27-C29 sterenes and stanols, 5ÎČ-cholesta-3-one, cholesta-3,5-diene and 2 thiosteranes. Except for thiosteranes and some of the C27-C29 cholestenes, the relative concentrations decreased during co-composting due to microbial degradation. The changes in steroids during co-composting, was positively correlated with the physico-chemical parameters of mature compost, especially C/N and NH4 +/NO3 - ratios, opening the way for the use of steroids as indicators of pollution and compost maturity. On the selective CTEA medium, 12 active strains of isolated actinobacteria presented a suppressive action against various pathogens. This may justify that a biotic factor is also an important factor contributing to making co-composting substrates hygienic. The degree hygiene reached is confirmed by the reduction in the faecal and total coliforms, and by the abatement of identified helminth eggs (Ascaris sp., Capillaria sp., and Trichuris sp.) towards the end of the process. The phytotoxicity determined by the effect of aqueous extract, at various stages of the co-composting, performed by monitoring the number of germinated seeds and the rootlets growth of turnip, watercress, alfalfa, and lettuce was decreased, and the growth of radicals that have a germination index that exceeds 100% after six months of co-composting. Hexavalent chromium (Cr(VI)) genotoxicity showed a positive correlation with micronucleus (MN) frequency. After six months of co-composting, the MN rate decreased significantly by 70.4 and 77.2% with decreasing Cr(VI) concentration with 58 and 58.6%, for mixtures A and B respectively. That indicates their suitability for use as a maturity index. During co-composting the abatement rate of phytotoxicity and genotoxicity confirme the maturation and stabilization degree of co-composting end products which encourages their recycling in agriculture as a fertilizer for the soil without any contamination of the soil-plant system
Advantages and Limitations of Using FTIR Spectroscopy for Assessing the Maturity of Sewage Sludge and Olive Oil Waste Co-composts
Composts prepared using different solid and liquid organic wastes from various sources can be used as growing media when these materials present adequate proprieties for plant development. The stability and maturity are among the main characteristics of composts. The purpose of this study is to recommend specific bands of the IR spectrum recorded on different composts to enable qualitative and rapid monitoring of the stages of biodegradation during composting. At the beginning of humification, the significant decrease in the intensity of the band located at 1735 cmâ1 shows that lignin is affected at the first stage of the composting process. At the end of the humification, the band located toward 3450â3420 cmâ1 at the beginning of the process undergoes a systematic shift (ÎÎœ of the order of 10 cmâ1) toward lower wave numbers. The band located at 1660â1650 cmâ1 on the Fourier transform infrared spectroscopy (FTIR) spectra before composting shifts systematically toward 1640 cmâ1 at the end of humification. This phenomenon can be used as index of compost maturity. Measuring the band at 1035 cmâ1 as an internal standard, it is possible to quantify the degradation rate of organic matter
Polycyclic aromatic hydrocarbons in citrus fruit irrigated with fresh water under arid conditions: Concentrations, sources, and risk assessment
In Jordan, as well as in all the world countries, consumption of citrus fruits is an essential part of the daily diet, so it is important to assess the potential risk of the persistent organic pollutants such as polyaromatic hydrocarbons (PAHs) in these fruits to the human health and identify their sources in order to eliminate or reduce them. This study reports 16 priority PAHs content in four types of peeled citrus fruits grown in Jordan valley. PAHs were detected in all the studied samples in variable quantities depending on the type of citrus fruits. The results showed that the highest PAH level corresponded to acenaphthene (35.018 ”g/kg) in grapefruit. Among the carcinogenic PAHs, benzo[a]anthracene (BaA) and benzo(a)pyrene (BaP) were the most representative and found in all the analyzed fruit, soil, and water samples, whereas anthracene (ANT) was not detected at all. The mean â16 PAHs for the different fruits were found to be 62.593 ”g kgâ1 in grapefruit, 24.840 ”g kgâ1 in lemon, 22.901 ”g kgâ1 in mandarin, and 5.082 ”g kgâ1 in orange. The dominance of naphthalene (NAP) and acenaphthene (ACE) in soil under hot climatic conditions indicates the recent and continuous input of these types in the investigated area. The bioconcentration factor (BCF) for â16 PAHs was observed in the order of grapefruit > lemon > mandarin > orange. Based on the results of the principal component analysis (PCA), the primary sources of PAHs in agricultural soils mainly originated from biomass burning and vehicular emissions. The incremental lifetime cancer risk (ILCR) indicated that consumption of these four citrus fruits may expose human health to potential cancer risk. The findings of this study call the policymakers and public administrations to the formulation of stringent policies and actions to control biomass burning and vehicular emissions
Assessment of the agronomic value of solar-dried sludge and heavy metals bioavailability based on the bioaccumulation factor and translocation index
This study aimed to assess the agronomic value of solar-dried sludge (SDS) and the transfer of Cr, Ni, Pb, and Cu to wheat (Triticum aestivum) and faba bean (Vicia faba). A greenhouse experiment was performed involving two rates of SDS (15Â t/ha and 30Â t/ha) from an activated sludge-based wastewater treatment plant. In addition to the single use of an SDS amendment, co-application of SDS and mineral fertilizers was also included to determine the best scenario resulting in high yields and less negative implications on the environment. Data for both wheat and faba bean showed that applying SDS at 30Â t/ha led to competitive yields compared to the ones obtained previously, while 15Â t/ha of SDS and mineral fertilizers were co-applied. The use of SDS increased soil organic matter, slightly decreased the pH value, and increased soil salinity. The contents of Ni, Cu, and Pb were not significantly affected by the application of SDS. Only Cr showed high soil concentrations in proportion to the increasing rates of SDS. The bioaccumulation of heavy metals in roots was more important in 30Â t/ha than that in 15Â t/ha amended soil. In the case of wheat, the bioconcentration factor (BCF) root values correspond to the following order: Cr (0.89) >Cu (0.85)> Ni (0.28)> Pb (0.22). In the case of faba bean, BCF roots were observed as follows: Cu (1.04 > Ni (0.37)> Cr (0.16)> Pb (0.15). Wheat excluded Cr, Ni, and Pb from the uptake by shoots, and Cu was translocated from roots to shoots with a percentage of 11% at 30Â t/ha of applied SDS. Faba beans demonstrated more important values of HMâs translocation by respecting this order (Ni (37.7%) > cu (30.24%)> Cr (17.59%), while Pb was excluded from the translocation. No significant difference was observed regarding the translocation index when the sludge rate has been duplicated from 15Â t/ha to 30Â t/ha. Based on these outcomes, SDS used at the rate of 30Â t/ha is the best scenario to amend the soil and provide nutrients to plants. Wheat is translocating less heavy metal to the edible part; it is, thus, the most suitable crop to be involved in the current context
Cr(VI) removal performance from wastewater by microflora isolated from tannery effluents in a semi-arid environment: a SEM, EDX, FTIR and zeta potential study
Hexavalent chromium removal from the environment remains a crucial worldwide challenge. To address this issue, microbiological approaches are amongst the straightforward strategies that rely mainly on the bacteria's and fungi's survival mechanisms upon exposure to toxic metals, such as reduction, efflux system, uptake, and biosorption. In this work, scanning electron microscopy, energy-dispersive X-ray spectrophotometry, Fourier transform infrared spectroscopy, and zeta potential measurements were used to investigate the ability of chromium adsorption by Bacillus licheniformis, Bacillus megaterium, Byssochlamys sp., and Candida maltosa strains isolated from tannery wastewater. Scanning electron microscopy combined with energy dispersive X-ray spectroscopy revealed alterations in the cells treated with hexavalent chromium. When exposed to 50 mg/L Cr6+, Bacillus licheniformis and Candida maltosa cells become rough, extracellular secretions are reduced in Bacillus megaterium, and Byssochlamys sp. cells are tightly bound and exhibit the greatest Cr weight percentage. In-depth analysis of Fourier transform infrared spectra of control and Cr-treated cells unveiled Cr-microbial interactions involving proteins, lipids, amino acids, and carbohydrates. These findings were supported by zeta potential measurements highlighting significant variations in charge after treatment with Cr(VI) with an adsorption limit of 100 mg/L Cr6+ for all the strains. Byssochlamys sp. showed the best performance in Cr adsorption, making it the most promising candidate for treating Cr-laden wastewater
physico-chemical microbiological and ecotoxicological monitoring during composting of sewage sludge-date palme waste : validation of new maturity index
Le traitement de boues de station d'Ă©puration (Boues activĂ©es de Marrakech) en mĂ©lange avec dĂ©chets verts (Palmier dattier) selon deux mĂ©langes dont les proportions : A (1/3 Boues + 2/3 DĂ©chets de palmier) et B (1/2 Boues + 1/2 DĂ©chets de palmier), a Ă©tĂ© effectuĂ© par la filiĂšre du compostage, pendant six mois. Au cours du co-compostage, lâintense activitĂ© microbienne sâest traduite par une augmentation de tempĂ©rature (autour 65 C°) au cours des premiĂšres semaines (phase thermophile) et un taux de dĂ©composition final de lâordre de 40%. AprĂšs six mois de co-compostage, le compost final est caractĂ©risĂ© par un rapport C/N voisin de 10, un rapport de NH4+/NO3- < 1, un pH autour de la neutralitĂ© signe de maturitĂ© des composts. Lâanalyse FTIR a montrĂ© une diminution de l'absorbance des bandes aliphatiques et l'augmentation de la structure de bandes d'absorbance aromatiques reflĂštent l'Ă©tat d'avancement du processus d'humification. Le taux dâabattement des lipides totaux est de lâordre de 43%. Les esters mĂ©thyliques dâacide gras (FAMEs) des Gram-positif (i,C15 :0) ont augmentĂ© durant la phase thermophile. Les FAMEs dâorigine non spĂ©cifique (C6 :0, C14 :0) ont connu une intense diminution, les FAMEs de bactĂ©ries non spĂ©cifiques reprĂ©sentent une grande teneur durant la phase thermophile. Lâindice CPI a augmentĂ© Ă la fin du co-compostage indiquant lâenrichissement du compost en FAMEs dâorigine vĂ©gĂ©tale. Les principaux composĂ©s ligneux identifiĂ©s, au cours du co-compostage, par Py-GC-MS, sont classĂ©s en deux groupes. Le premier est constituĂ© de 7 composĂ©s dont la teneur diminue au cours du co-compostage, parmi lesquels : ToluĂšne, 2,4-dimĂ©thylbenzĂšne, Ă©thylbenzĂšne, StyrĂšne, 1-Ă©thyl-2-mĂ©thylbenzĂšne, 4-mĂ©thylphĂ©nol et 2-mĂ©thylnaphthalĂšne. Le deuxiĂšme groupe est constituĂ© de 4 composĂ©s qui augmentent au cours du co-compostage : phĂ©nol, benzofuran, Ă©thylmĂ©thoxyphĂ©nol et dimĂ©thoxyphĂ©nol. Les principaux stĂ©roĂŻdes identifiĂ©s sont les C27-C29 sterĂšnes, stanols, 5ÎČ-cholesta-3-one, cholesta-3,5-diĂšne et 2 thiostĂ©ranes. A lâexception des thiosteranes et quelques composĂ©s de C27-C29 cholestenes la concentration relative des stĂ©roides diminue au cours du processus suit Ă leur attaque microbien. Lâabattement total de la teneur des stĂ©roĂŻdes est corrĂ©lĂ© positivement avec les indicateurs de maturitĂ© du compost (C/N et NH4+/NO3-) ce qui ouvre la voie Ă une Ă©ventuelle utilisation des stĂ©roĂŻdes comme indicateur de dĂ©pollution et de maturitĂ© de compost. 12 isolats dâactinomycĂštes ayant une activitĂ© antimicrobienne vis-Ă -vis dâun large spectre des germes pathogĂšnes ont Ă©tĂ© isolĂ©s sur le milieu sĂ©lectif CTEA. Le degrĂ© dâhygiĂ©nisation est confirmĂ© par la diminution de la concentration des coliformes fĂ©caux et totaux, et lâabattement des Ćufs dâhelminthes identifiĂ©s (Ascaris sp., Capillaria sp., et Trichuris sp.) vers la fin du co-compostage. La phytotoxicitĂ©, dĂ©terminĂ©e par lâeffet des extraits hydrosolubles Ă diffĂ©rents stades de co-compostage sur la germination et la croissance des radicules (Navet, Cresson, Laitue, Luzerne), a diminuĂ© et lâindice de germination dĂ©passe 100%, aprĂšs six mois de co-compostage. La gĂ©notoxicitĂ© du chrome hexavalent (Cr(VI)) du substrat de co-compostage est corrĂ©lĂ©e positivement avec la frĂ©quence des micronoyaux (MN). AprĂšs six mois de co-compostage le taux des MN diminue avec un taux dâabattement de 70,4% et 77,2% avec lâabattement de la concentration du Cr(VI) avec 58 et 58,6% respectivement pour le mĂ©lange A et B. Ceci ouvrira la voie dâutilisation de cet indice comme un indice de maturitĂ© des composts. La diminution de la phytotoxicitĂ© et la gĂ©notoxictĂ© au cours du co-compostage confirme lâĂ©tat de stabilisation et de la maturitĂ© des co-composts, ce qui pemettra lâĂ©pandage de ces composts en tant quâamendement organique des sols sans risque de contamination du systĂšme sol-plante.The co-composting of activated sludge and lignocellulose waste (palm tree waste) was monitored to study the behaviour of two mixtures, referred to as A (1/3 sludge + 2/3 palm waste) and B (1/2 sludge + 1/2 waste palm) for 6 months. The biotransformation was evaluated by physicochemical and spectroscopic analyses. The thermophilic phase is characterized by a rise in temperature, which peaked at 65°C. This is the result of intense microbial activities. The final composts exhibited a higher degree of decomposition than the controls as shown by a decomposition rate of about 40%, decrease of C/N ratio to around 10 and NH4 +/NO3 - ratio below 1. The decrease of aliphatic absorbance bands and the increase of aromatic absorbance bands follow the progress of the humification process. Total extractable lipid was decreased by 43%. The fatty acid methyl esters (FAMEs) from Gram-positive bacteria (i, C15: 0) increased during the thermophilic phase. FAMEs from non-spĂ©cific origin (C6 :0, C14 :0) exhibited a decrease toward the end of co-compostin, linear FAMEs from non-specific bacteria underwent a decrease during co-composting. The CPI index thus increased at the end of the composting process, indicating that the final product was proportionally richer in fatty acids of plant origin. Two lignin groups were distinguished by Py-GC-MS. Group 1 contained toluene, 2,4-dimethylbenzene, ethylbenzene, styrene, 1-ethyl-2-methylbenzene, 4-methylphenol and 2-methylnaphthalene; their relative proportions decreased during co-composting. A second group of 4 components showed concentrations that increased with co-composting time: phenol, benzofuran, ethylmethoxyphenol and dimethoxyphenol. The main steroids identified were C27-C29 sterenes and stanols, 5ÎČ-cholesta-3-one, cholesta-3,5-diene and 2 thiosteranes. Except for thiosteranes and some of the C27-C29 cholestenes, the relative concentrations decreased during co-composting due to microbial degradation. The changes in steroids during co-composting, was positively correlated with the physico-chemical parameters of mature compost, especially C/N and NH4 +/NO3 - ratios, opening the way for the use of steroids as indicators of pollution and compost maturity. On the selective CTEA medium, 12 active strains of isolated actinobacteria presented a suppressive action against various pathogens. This may justify that a biotic factor is also an important factor contributing to making co-composting substrates hygienic. The degree hygiene reached is confirmed by the reduction in the faecal and total coliforms, and by the abatement of identified helminth eggs (Ascaris sp., Capillaria sp., and Trichuris sp.) towards the end of the process. The phytotoxicity determined by the effect of aqueous extract, at various stages of the co-composting, performed by monitoring the number of germinated seeds and the rootlets growth of turnip, watercress, alfalfa, and lettuce was decreased, and the growth of radicals that have a germination index that exceeds 100% after six months of co-composting. Hexavalent chromium (Cr(VI)) genotoxicity showed a positive correlation with micronucleus (MN) frequency. After six months of co-composting, the MN rate decreased significantly by 70.4 and 77.2% with decreasing Cr(VI) concentration with 58 and 58.6%, for mixtures A and B respectively. That indicates their suitability for use as a maturity index. During co-composting the abatement rate of phytotoxicity and genotoxicity confirme the maturation and stabilization degree of co-composting end products which encourages their recycling in agriculture as a fertilizer for the soil without any contamination of the soil-plant system
Occurrence, analysis of microplastics in sewage sludge and their fate during composting: A literature review
International audienceMicroplastics (MP) are ubiquitous contaminants and their presence in sewage sludge has recently received attention as they may enter agro-ecosystems if sludge is used as organic soil amendment. Indeed, plastic particles (<5 mm) can be transported from wastewater and sewage sludge to the soil environment either directly within the plastic matrix or indirectly as adsorbed substances. In this paper, articles from 18 countries reporting the MP quantity and their characteristics in sewage sludge from wastewater treatment plants were reviewed and the MP concentration size and type were compared. The data show that MP abundance in sewage sludge ranged globally from 7.91 to 495 x 10(3) particles kg(-1) with highest abundance of fiber shape and MP size of less than 500 mu m.In this review, we summarized and discussed the methods most frequently used for extraction and characterization of MP in sewage sludge including organic matter removal, MP extraction; physical and morphological MP characterization and its chemical characterization for polymer identification. We also described the major factors potentially controlling the fate of MP during disposal strategies with particular focus on composting. We show that physical and microbiological factors are important for MP degradation during composting and suggest two remediation practices: (i) inoculation of the initial sludge with microbial plastic decomposers to remove MP from contaminated sewage sludge, and (ii) development of high temperature composting processes
Identification and biotransformation of aliphatic hydrocarbons during co-composting of sewage sludge-Date Palm waste using Pyrolysis-GC/MS technique
International audienc
Identification and biotransformation of lignin compounds during co-composting of sewage sludge-palm tree waste using pyrolysis-GC/MS
International audienceThe biotransformation of lignin components during co-composting of sewage sludge activated with palm tree waste was studied for six months using Py-GC-MS. Two main groups of compounds were distinguished. The first includes 7 compounds which occurred during the co-composting process listed here in decreasing order of abundance: toluene, 2,4-dimethylbenzene, ethylbenzene, styrene, 1-ethyl-2- methylbenzene, 4-methylphenol and 2-methylnaphthalene. The reduction of their concentrations during the process is due to metabolization and biotransformation into other compounds. A second group of 4 components showed concentrations that increased with co-composting time: phenol, benzofuran, ethylmethoxyphenol and dimethoxyphenol. These lignin constituents are probably released parallel with lignin degradation to become incorporated into humic substances
Evaluation of lignocelullose compost stability and maturity using spectroscopic (FTIR) and thermal (TGA/TDA) analysis
International audienceThe follow-up of different physico-chemical parameters (TOC, TKN, C/N) over 14 months showed more rapid composting and greater maturation for the DPGC compost (containing a mixture of date palm waste with couch-grass clippings waste) than for the DPW compost (containing date palm waste alone). Simultaneous mineralization and nitrification phenomena were recorded throughout both composting, this indicate a gradual degradation of date palm waste. The final values of N-NH4+ in both composting showed that maturity was not achieved yet. FTIR analysis showed that both composts were rich in aromatic, phenolic, aliphatic and polysaccharidic structures. The characteristic ratios of IR bands (RIR) showed aromatization of the organic matter in the two composts, higher in the DPGC compost parallel with an advanced maturation. The TGA/DTA analysis showed that the OM transformations were less extensive in DPW compost. The values of the RTGA ratios gave the same end value for both composts, indicating that this index does not correctly assess biological stability. The variations recorded in mass losses associated to exothermal peaks showed that the transformations of OM did not lead to aromatization but rather to functionalization of the OM. (C) 2014 Elsevier B.V. All rights reserved