Bilan du carbone dans le lagunage anaérobie appliqué sous climat méditerranéen

Ce travail a porté sur l'application du lagunage anaérobie pour le traitement primaire des eaux résiduaires urbaines sous climat méditerranéen. Il a été réalisé sur les lagunes anaérobies de l' Ecosite de Mèze (Hérault, France). Les lagunes anaérobies constituent un traitement primaire satisfaisant avec des rendements moyens de 55% pour les MES et 30% pour la DBO5, pour une faible emprise au sol. Le taux d'accumulation des boues est de seulement 0,017 m3 /EH.an, notamment du fait de l'efficacité de la dégradation anaérobie. L'équilibre du métabolisme anaérobie des boues est atteint après un an de fonctionnement. L'accumulation des boues se fait alors de façon saisonnière avec une forte accumulation en hiver et une digestion du stock en été. Cette évolution est liée à l'influence de la température sur la méthanogénèse. La production de biogaz (83% CH4) a pu être mesurée par des collecteurs à gaz mis au point pour cette étude et dépend également fortement de la température. Le bilan du carbone montre que 74% du carbone organique épuré est converti en CH4, 13% en carbone inorganique dissous et seulement 15% est stocké dans les boues. Toutefois, les lagunes anaérobies présentent un risque de créer des nuisances olfactives dues à l'émission de H2 S.This project examined the application of anaerobic ponds for the primary treatment of urban wastewater under a Mediterranean climate. The objectives of the study were to determine removal performances and to study sludge accumulation and the production of biogas. Together, these results allowed us to calculate the carbon mass balance in the anaerobic ponds.This work was carried out in the two large primary anaerobic ponds of the waste stabilization pond system at the Ecosite of Mèze (Hérault, France), treating domestic wastewater for 13,800 person-equivalents (PE). Anaerobic ponds were 5,000 m3 in volume, 3.1 m in depth and presented a retention time of 4.6 d with a mean volumetric organic loading of 83 g BOD5 /m3 ×d× The characteristics of the influent and effluent (including: suspended solids (SS); chemical oxygen demand (COD); biological oxygen demand (BOD5); bicarbonate (HCO3 -); total organic carbon (TOC); and volatile fatty acids (VFA)) were determined twice-monthly. The volume of sludge and its characteristics (including: SS; volatile solids (VS); TOC; and VFA) were measured monthly. The production of biogas and its composition (CH4, CO2, H2 S) were measured with gas collectors specially developed for this study.Results showed that the anaerobic ponds constituted a good primary treatment with mean removal rates of 55% for SS, 30% for BOD and 22% for COD. Removal performances were relatively constant over the year. Indeed, removal rates were essentially due to the removal of particulate organic matter by sedimentation. Anaerobic degradation occurred essentially in the sludge layer and the removal of soluble COD was low.The study of sludge characteristics showed that anaerobic digestion equilibrium was reached after one year of operation. The beginning of methanogenesis could be observed by the decrease in the concentration of volatile fatty acids. The accumulation of sludge showed seasonal variation with an important accumulation in winter and the digestion of the accumulated stock in summer. This evolution could be related to the influence of temperature on methanogenesis. The mean rate of sludge accumulation was only 3.8 g SS/P-E×d or 0.017 m3/P-E×yr. This rate was significantly lower than for the primary settling tank (50-60 g SS/P-E×d) and for the facultative ponds (0.085 m3 /P-E×yr) due to the intensive anaerobic degradation.The production of biogas was measured by gas collectors specially developed for this study. The biogas contained essentially CH4 (83%); CO2 was less than 4% because it dissolved in the water column and was converted into bicarbonate alkalinity. The concentration of H2 S was less than 1% (between 75 and 4770 ppm) but was the cause of unpleasant odours. The biogas production rate was strongly dependent on temperature. A non-linear relationship was obtained (Ebiogas=4.8451 × e0.1203T, r2=0.92, n=16). The mean annual biogas production rate was calculated to be 49 L/m2 ×d. Seasonal variation in the biogas production rate could be related to seasonal variations in sludge accumulation.The carbon mass balance showed that 74% of the removed organic carbon was converted into CH4, 13% into dissolved inorganic carbon (bicarbonates) and only 15% was stored in sludge. The mass balance was well equilibrated and did not show the entry of atmospheric CO2, which occurs in aerobic ponds where CO2 is used by algae to produce their cell biomass. In an anaerobic pond, the low production of sludge was due to the efficiency of the anaerobic degradation but also to the low internal biomass production.To conclude, the use of a primary anaerobic pond was advantageous and permitted a reduction in the required surface area for a waste stabilization pond system. This process produced effluent for secondary treatment in a facultative pond with essentially the removal of the particulate organic matter. However, However, anaerobic ponds may cause odor problems linked to the emission of H2 S

The grid-minor theorem revisited

We prove that for every planar graph $X$ of treedepth $h$, there exists a positive integer $c$ such that for every $X$-minor-free graph $G$, there exists a graph $H$ of treewidth at most $f(h)$ such that $G$ is isomorphic to a subgraph of $H\boxtimes K_c$. This is a qualitative strengthening of the Grid-Minor Theorem of Robertson and Seymour (JCTB 1986), and treedepth is the optimal parameter in such a result. As an example application, we use this result to improve the upper bound for weak coloring numbers of graphs excluding a fixed graph as a minor

Glyphosate and AMPA in human urine of HBM4EU-aligned studies: part B adults

Within HBM4EU, human biomonitoring (HBM) studies measuring glyphosate (Gly) and aminomethylphosphonic acid (AMPA) in urine samples from the general adult population were aligned and quality-controlled/assured. Data from four studies (ESB Germany (2015-2020); Swiss HBM4EU study (2020); DIET-HBM Iceland (2019-2020); ESTEBAN France (2014-2016)) were included representing Northern and Western Europe. Overall, median values were below the reported quantification limits (LOQs) (0.05-0.1 microg/L). The 95th percentiles (P95) ranged between 0.24 and 0.37 microg/L urine for Gly and between 0.21 and 0.38 microg/L for AMPA. Lower values were observed in adults compared to children. Indications exist for autonomous sources of AMPA in the environment. As for children, reversed dosimetry calculations based on HBM data in adults did not lead to exceedances of the ADI (proposed acceptable daily intake of EFSA for Gly 0.1 mg/kg bw/day based on histopathological findings in the salivary gland of rats) indicating no human health risks in the studied populations at the moment. However, the controversy on carcinogenicity, potential endocrine effects and the absence of a group ADI for Gly and AMPA induce uncertainty to the risk assessment. Exposure determinant analysis showed few significant associations. More data on specific subgroups, such as those occupationally exposed or living close to agricultural fields or with certain consumption patterns (vegetarian, vegan, organic food, high cereal consumer), are needed to evaluate major exposure sources

A human biomonitoring (HBM) Global Registry Framework: Further advancement of HBM research following the FAIR principles.

Data generated by the rapidly evolving human biomonitoring (HBM) programmes are providing invaluable opportunities to support and advance regulatory risk assessment and management of chemicals in occupational and environmental health domains. However, heterogeneity across studies, in terms of design, terminology, biomarker nomenclature, and data formats, limits our capacity to compare and integrate data sets retrospectively (reuse). Registration of HBM studies is common for clinical trials; however, the study designs and resulting data collections cannot be traced easily. We argue that an HBM Global Registry Framework (HBM GRF) could be the solution to several of challenges hampering the (re)use of HBM (meta)data. The aim is to develop a global, host-independent HBM registry framework based on the use of harmonised open-access protocol templates from designing, undertaking of an HBM study to the use and possible reuse of the resulting HBM (meta)data. This framework should apply FAIR (Findable, Accessible, Interoperable and Reusable) principles as a core data management strategy to enable the (re)use of HBM (meta)data to its full potential through the data value chain. Moreover, we believe that implementation of FAIR principles is a fundamental enabler for digital transformation within environmental health. The HBM GRF would encompass internationally harmonised and agreed open access templates for HBM study protocols, structured web-based functionalities to deposit, find, and access harmonised protocols of HBM studies. Registration of HBM studies using the HBM GRF is anticipated to increase FAIRness of the resulting (meta)data. It is also considered that harmonisation of existing data sets could be performed retrospectively. As a consequence, data wrangling activities to make data ready for analysis will be minimised. In addition, this framework would enable the HBM (inter)national community to trace new HBM studies already in the planning phase and their results once finalised. The HBM GRF could also serve as a platform enhancing communication between scientists, risk assessors, and risk managers/policy makers. The planned European Partnership for the Assessment of Risk from Chemicals (PARC) work along these lines, based on the experience obtained in previous joint European initiatives. Therefore, PARC could very well bring a first demonstration of first essential functionalities within the development of the HBM GRF

Time Trends of Acrylamide Exposure in Europe: Combined Analysis of Published Reports and Current HBM4EU Studies

More than 20 years ago, acrylamide was added to the list of potential carcinogens found in many common dietary products and tobacco smoke. Consequently, human biomonitoring studies investigating exposure to acrylamide in the form of adducts in blood and metabolites in urine have been performed to obtain data on the actual burden in different populations of the world and in Europe. Recognizing the related health risk, the European Commission responded with measures to curb the acrylamide content in food products. In 2017, a trans-European human biomonitoring project (HBM4EU) was started with the aim to investigate exposure to several chemicals, including acrylamide. Here we set out to provide a combined analysis of previous and current European acrylamide biomonitoring study results by harmonizing and integrating different data sources, including HBM4EU aligned studies, with the aim to resolve overall and current time trends of acrylamide exposure in Europe. Data from 10 European countries were included in the analysis, comprising more than 5500 individual samples (3214 children and teenagers, 2293 adults). We utilized linear models as well as a non-linear fit and breakpoint analysis to investigate trends in temporal acrylamide exposure as well as descriptive statistics and statistical tests to validate findings. Our results indicate an overall increase in acrylamide exposure between the years 2001 and 2017. Studies with samples collected after 2018 focusing on adults do not indicate increasing exposure but show declining values. Regional differences appear to affect absolute values, but not the overall time-trend of exposure. As benchmark levels for acrylamide content in food have been adopted in Europe in 2018, our results may imply the effects of these measures, but only indicated for adults, as corresponding data are still missing for children

Trends of Exposure to Acrylamide as Measured by Urinary Biomarkers Levels within the HBM4EU Biomonitoring Aligned Studies (2000–2021)

Acrylamide, a substance potentially carcinogenic in humans, represents a very prevalent contaminant in food and is also contained in tobacco smoke. Occupational exposure to higher concentrations of acrylamide was shown to induce neurotoxicity in humans. To minimize related risks for public health, it is vital to obtain data on the actual level of exposure in differently affected segments of the population. To achieve this aim, acrylamide has been added to the list of substances of concern to be investigated in the HBM4EU project, a European initiative to obtain biomonitoring data for a number of pollutants highly relevant for public health. This report summarizes the results obtained for acrylamide, with a focus on time-trends and recent exposure levels, obtained by HBM4EU as well as by associated studies in a total of seven European countries. Mean biomarker levels were compared by sampling year and time-trends were analyzed using linear regression models and an adequate statistical test. An increasing trend of acrylamide biomarker concentrations was found in children for the years 2014–2017, while in adults an overall increase in exposure was found to be not significant for the time period of observation (2000–2021). For smokers, represented by two studies and sampling for, over a total three years, no clear tendency was observed. In conclusion, samples from European countries indicate that average acrylamide exposure still exceeds suggested benchmark levels and may be of specific concern in children. More research is required to confirm trends of declining values observed in most recent years

Developing human biomonitoring as a 21st century toolbox within the European exposure science strategy 2020-2030

Human biomonitoring (HBM) is a crucial approach for exposure assessment, as emphasised in the European Commission's Chemicals Strategy for Sustainability (CSS). HBM can help to improve chemical policies in five major key areas: (1) assessing internal and aggregate exposure in different target populations; 2) assessing exposure to chemicals across life stages; (3) assessing combined exposure to multiple chemicals (mixtures); (4) bridging regulatory silos on aggregate exposure; and (5) enhancing the effectiveness of risk management measures. In this strategy paper we propose a vision and a strategy for the use of HBM in chemical regulations and public health policy in Europe and beyond. We outline six strategic objectives and a roadmap to further strengthen HBM approaches and increase their implementation in the regulatory risk assessment of chemicals to enhance our understanding of exposure and health impacts, enabling timely and targeted policy interventions and risk management. These strategic objectives are: 1) further development of sampling strategies and sample preparation; 2) further development of chemical-analytical HBM methods; 3) improving harmonisation throughout the HBM research life cycle; 4) further development of quality control / quality assurance throughout the HBM research life cycle; 5) obtain sustained funding and reinforcement by legislation; and 6) extend target-specific communication with scientists, policymakers, citizens and other stakeholders. HBM approaches are essential in risk assessment to address scientific, regulatory and societal challenges. HBM requires full and strong support from the scientific and regulatory domain to reach its full potential in public and occupational health assessment and in regulatory decision-making