Machine learning models based on molecular descriptors to predict human and environmental toxicological factors in continental freshwater

It is a real challenge for life cycle assessment practitioners to identify all relevant substances contributing to the ecotoxicity. Once this identification has been made, the lack of corresponding ecotoxicity factors can make the results partial and difficult to interpret. So, it is a real and important challenge to provide ecotoxicity factors for a wide range of compounds. Nevertheless, obtaining such factors using experiments is tedious, time-consuming, and made at a high cost. A modeling method that could predict these factors from easy-to-obtain information on each chemical would be of great value. Here, we present such a method, based on machine learning algorithms, that used molecular descriptors to predict two specific endpoints in continental freshwater for ecotoxicological and human impacts. The method shows good performances on a learning database. Then, predictions were derived from the validated model for compounds with missing toxicity/ecotoxicity factors

Evidence for PAH Removal Coupled to the First Steps of Anaerobic Digestion in Sewage Sludge

Anaerobic degradation of polycyclic aromatic hydrocarbons has been brought to the fore, but information on removal kinetics and anaerobic degrading bacteria is still lacking. In order to explore the organic micropollutants removal kinetics under anaerobic conditions in regard to the methane production kinetics, the removal rate of 12 polycyclic aromatic hydrocarbons was measured in two anaerobic batch reactors series fed with a highly loaded secondary sludge as growth substrate. The results underscore that organic micropollutants removal is coupled to the initial stages of anaerobic digestion (acidogenesis and acetogenesis). In addition, the organic micropollutants kinetics suggest that the main removal mechanisms of these hydrophobic compounds are biodegradation and/or sequestration depending on the compounds

Anaerobic Removal of Trace Organic Contaminants in Sewage Sludge: 15 Years of Experience

Trace organic contaminants (TOCs) correspond to a broad range of molecules generated either directly or indirectly by human activity. Even though TOCs are found at low concentrations in the environment, they often accumulate by biomagnification and bioaccumulation into biological organisms and cause irreversible damages in biological systems through direct or indirect toxic effects such as endocrine disruption and tumour initiation. This manuscript presents the main findings of over fifteen years of research focusing on biological removal of various TOCs found in sewage sludge from urban treatment plants. A special focus of the research was made on microbial processes in complex anaerobic ecosystems. Four families of compounds mostly retrieved in urban plants were studied: the polycyclic aromatic hydrocarbons (PAHs), the polychlorobiphenyls (PCBs), the phthalic acid esters (PAEs), and the nonylphenol ethoxylates (NPEs). It was observed that the microbial capability for removing low amounts of TOCs required a long adaptation time and was often limited by the bioavailability of these compounds. In fact, the overall biodegradation resulted from the numerous interactions existing between the matrix (organic matter) and the microbial ecosystems according to the physico-chemical sorption properties of these compounds. Mechanistic aspects were also tackled in depth and specific models were developed for better understanding the network of interactions between TOCs, microorganisms, and organic matter. These findings could be extrapolated to other ecosystems such as soils and sediments. Finally, it was shown that microbial cometabolism was essential for TOC removal, and the concept of bioavailability was not only dependent on the nature, the level, and the sorption properties of TOCs but was also strongly dependent on the nature and the concentration of the sludge organic matter. Specific parameters were proposed for better evaluating the fate of TOCs in microbial anaerobic processes and technological solutions for efficient removal of these compounds were also proposed

Categorizing chlordecone potential degradation products to explore their environmental fate

EA BIOmE SUPDAT INRAInternational audienceChlordecone (C10Cl10O; CAS number 143-50-0) has been used extensively as an organochlorine insecticide but is nowadays banned and listed on annex A in The Stockholm Convention on Persistent Organic Pollutants (POPs). Although experimental evidences of biodegradation of this compound are scarce, several dechlorination products have been proposed by Dolfing et al. (2012) using Gibbs free energy calculations to explore different potential transformation routes. We here present the results of an in silico classification (TyPol - Typology of Pollutants) of chlordecone transformation products (TPs) based on statistical analyses combining several environmental endpoints and structural molecular descriptors. Starting from the list of putative chlordecone TPs and considering available data on degradation routes of other organochlorine compounds, we used different clustering strategies to explore the potential environmental behaviour of putative chlordecone TPs from the knowledge on their molecular descriptors. The method offers the possibility to focus on TPs present in different classes and to infer their environmental fate. Thus, we have deduced some hypothetical trends for the environmental behaviour of TPs of chlordecone assuming that TPs, which were clustered away from chlordecone, would have different environmental fate and ecotoxicological impact compared to chlordecone. Our findings suggest that mono- and di-hydrochlordecone, which are TPs of chlordecone often found in contaminated soils, may have similar environmental behaviour in terms of persistence

Les interactions Perturbateurs EndoCriniens-MICroorganismes et Matières OrGaniques, moteurs de l’écodynamique et de l’impact des polluants au sein d’écosystèmes épuratoires

MEMBRES DU PROJET ISM-LPTC UMR 5255 Université Bordeaux I : Marie-Ange Cordier, Karyn Le Menach, Hélène Budzinski, Edith Parlanti, INERIS Verneuil en Halatte : Selim Ait-Aissa, Nicolas Creusot, Emmanuelle Maillot-Maréchal IRSTEA Antony : Carolina Hoyos-Hernandez, Angeline Guenne, Céline Madigou, Théodore Bouchez, Laurent Mazeas INRA LBE Narbonne : Florence Braun, Glenda Cea-Barcia, Liliana Delgadillo-Mirquez, Nadine Delgenès, Gaelle Gevaudan-Santa Catalina, Anais Bonnafous, Jérôme Hamelin, Hélène Carrère, Dominique PatureauLe présent projet vise à contribuer à l’évaluation et à la réduction des risques environnementaux de pollution chimique de l’environnement, associés aux perturbateurs endocriniens (PE) présents dans des produits résiduaires utilisés en agriculture. Cet objectif général se décompose en objectifs spécifiques liés à l’une des composantes du risque, l’exposition. Cette exposition sera caractérisée via le développement et la validation d’indicateurs de la disponibilité des polluants. Ces indicateurs seront identifiés au travers de l’observation multi-échelle des interactions entre les polluants, les microorganismes (le vivant) et l’environnement matriciel dans lequel ils évoluent. En effet, c’est de l’interaction de ces trois composantes que naît la dynamique des polluants dans un environnement tel que celui des procédés de traitement. Une meilleure compréhension de ces interactions et des processus qui y sont liés nous permettra de mieux appréhender la dynamique des polluants, de la modéliser et contribuera significativement à l’évaluation des risques (indicateurs de disponibilité) et à leur réduction au travers de la proposition de stratégies de traitement. Pour ce faire, nous proposons de développer une approche intégrée combinant les visions des microbiologistes, chimistes-géochimistes et écotoxicologues au coeur d’un procédé modèle de digestion anaérobie traitant des boues urbaines multi- et faiblement contaminées en PE

Successful treatment of low PAH-contaminated sewage sludge in aerobic bioreactors

International audiencePolycyclic Aromatic Hydrocarbons (PAHs) are known for their adverse and cumulative effects at low concentration. In particular, the PAHs accumulate in sewage sludge during wastewater treatment, and may thereafter contaminate agricultural soils by spreading sludge on land. Therefore, sludge treatment processes constitute the unique opportunity of PAH removal before their release in the environment. In this study, the ability of aerobic microorganisms to degrade light and heavy PAHs was investigated in continuous bioreactors treating trace-level PAH-contaminated sludge

Devenir des perturbateurs endocriniens HAPs/NP/PCBs au cours de la digestion anaérobie de boues contaminées (rôle de la biodisponibilité et du cométabolisme)

Cette étude porte sur les mécanismes qui déterminent la biodégradation des HAPs/NP/PCBs au cours de la digestion anaérobie de boues contaminées. Etant admis que les phénomènes de sorption conditionnent la biodisponibilité des HAPs/NP/PCBs envers les microorganismes épurateurs, les transferts de sorption/désorption ont tout d'abord été étudiés. Ils s'opèrent quasi-instantanément, en référence aux cinétiques de biodégradation, et sont réversibles, même après un long temps de contact. Ensuite, une méthodologie a été conçue afin de mesurer les constantes d'équilibre qui déterminent la répartition de HAPs/NP/PCBs entre les trois compartiments de la boue : libre, sorbé à la matière dissoute et colloïdale (DCM), et sorbé aux particules. L'influence des caractéristiques des HAPs/NP/PCBs et des caractéristiques physiques et chimiques des boues sur les constantes d'équilibre a été quantifiée. Les modèles générés ont rendu possible la prédiction de la distribution des HAPs/NP/PCBs entre les trois compartiments, dans 5 digesteurs continus alimentés en différentes boues. La confrontation de cette répartition aux vitesses de dégradation des HAPs a mis en évidence que les HAPs libres mais aussi ceux sorbés à la DCM sont biodisponibles. De plus, la double influence de la biodisponibilité et du cométabolisme sur la biodégradation des HAPs a été suggérée, de sorte qu'aucun de ces processus ne peut être admis comme l'unique limitationThis study deals with the mechanisms which drive the biodegradation of PAHs/NP/PCBs during the anaerobic digestion of contaminated sludge. As the bioavailability of micropollutants is widely assumed to be linked to sorption phenomena, they were firstly investigated. It was demonstrated that PAHs sorption/desorption transfers are instantaneous, in comparison to biodegradation kinetics. Moreover, these transfers are reversible, even after a long period of contact between PAHs and sludge. To study the equilibrium state resulting from these transfers, a methodology was designed, considering sludge as a three-compartment matrix. Indeed, micropollutants in sludge can be either free, sorbed-to-DCM (dissolved and colloidal matter) or sorbed-to-particles. The influence of micropollutants characteristics and of physical and chemical sludge characteristics on equilibrium constants was quantified. The subsequent models allowed to predict the distribution of micropollutants between the three compartments within 5 continuous anaerobic digestors, fed with different sludge. The confrontation of compartment distributions to biodegradation rates revealed that both free and sorbed-to-DCM PAHs are bioavailable. Moreover, a shared limitation by bioavailability and by cometabolism flux was stated, suggesting that micropollutants removal is not limited by only one phenomenonMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Innocuité et efficacité de boues urbaines diversement transformées

Innocuité et efficacité de boues urbaines diversement transformées. 2èmes Journées Nationales de la Fertilisation Organiqu

Quelle place pour la méthanisation dans la gestion de la matière organique à l'échelle de l'agrosystème ?

Quelle place pour la méthanisation dans la gestion de la matière organique à l'échelle de l'agrosystème ?. Journées Recherche et Industrie Biogaz méthanisatio