Microplastic accumulation in sewer sediments and its potential entering the environment via combined sewer overflows: a study case in Paris.

During wet weather events, combined sewer overflows (CSOs) transfer large amount of particulate matter and associated pollutants into surrounding water bodies, thereby deteriorating the recipients' ecological health. Resuspension of sewer sediments during these events contributes significantly to pollution level of these discharges. However, how much this in-sewer process contributes to CSOs' quality regarding microplastic (MP) pollution is little known. Therefore, an investigation on sewer deposits inside the Parisian combined sewer network was carried out. The study found high MP concentrations stored in this matrix, ranging from 5 × 103 to 178 × 103 particle/kg dry weight. Polymer composition is similar to what found in raw wastewater, containing a high proportion of polyethylene and polypropylene. Thus, the results indicated the persistence of MPs in sewer network during transport during dry weather periods to treatment facilities. Once resuspension of sewer deposits happens, MPs can be released into water flow and get discharged along with CSOs. This highlights another potential pathway of MPs into freshwater environment.

COVID lockdown significantly impacted microplastic bulk atmospheric deposition rates.

Here, microplastic atmospheric deposition data collected at an urban site during the French national lockdown of spring 2020 is compared to deposition data from the same site in a period of normal activity. Bulk atmospheric deposition was collected on the vegetated roof of a suburban campus from the Greater Paris and analysed for microplastics using a micro-FTIR imaging methodology. Significantly lower deposition rates were measured overall during the lockdown period (median 5.4 MP m-2.d-1) than in a period of normal activity in spring 2021 (median of 29.2 MP m-2.d-1). This difference is however not observed for the smallest microplastic size class. The dominant polymers identified were PP, followed by PE and PS. Precipitation alone could not explain the differences between the two campaigns, and it is suggested that the temporary drop in human activity during lockdown is the primary cause of the reduced deposition rates. This study provides novel insight on the immediate impact of human activities on atmospheric microplastics, thus enhancing the global understanding on this topic.

Realistic assessment of tire and road wear particle emissions and their influencing factors on different types of roads.

This study aims to examine tire and road wear particle (TRWP) emissions under realistic conditions in order to provide some valuable insights into understanding their sources and fate in the environment. TRWP emissions were evaluated with a fully instrumented vehicle driving on five representative road types: urban, ring road, suburban, highway, and rural. Multiple vehicle dynamic variables were recorded to assess the factors influencing these emissions. For the first time, emitted particles were collected on filters and analyzed by means of pyrolysis coupled with gas chromatography-mass spectrometry to determine the polymeric content of tires, in specifically quantifying styrene-butadiene rubber (SBR) and butadiene rubber (BR) pyrolytic markers. The measurements obtained from the five road types revealed similar size distributions for SBR + BR emissions, with maxima found in the (ultra)fine fraction (< 0.39 µm). Upon applying an SBR + BR-to-TRWP conversion factor, (ultra)fine fraction TRWP emissions proved to be the highest for suburban (64 ± 5 µg/km), followed by highway, urban, ring road and rural routes. The output represents up to 480 tons of TRWP per year emitted in the EU27, thus suggesting a widely impregnated atmospheric compartment capable of threatening human health. Furthermore, an analysis of variables revealed that acceleration, tire constraints, and constant sustained driving factors had specific impacts on TRWP emissions.

Effect of an environmental microplastic mixture from the Seine River and one of the main associated plasticizers, dibutylphthalate, on the sentinel species Hediste diversicolor.

The aim of this study was to explore the adverse effects of a microplastic (MP) mixture obtained from litter accumulated in the Seine River (France) compared to those of their major co-plasticizer, dibutylphthalate (DBP), on the sentinel species Hediste diversicolor. A suite of biomarkers has been investigated to study the impacts of MPs (100 mg kg-1 sediment), DBP (38 µg kg-1 sediment) on worms compared to non-exposed individuals after 4 and 21 days. The antioxidant response, immunity, neurotoxicity and energy and respiratory metabolism were investigated using biomarkers. After 21 days, worms exposed to MPs showed an increasing aerobic metabolism, an enhancement of both antioxidant and neuroimmune responses. Energy-related biomarkers demonstrated that the energy reallocated to the defence system may come from proteins. A similar impact was depicted after DBP exposure, except for neurotoxicity. Our results provide a better understanding of the ecotoxicological effects of environmental MPs and their associated-contaminants on H. diversicolor.

Toxicity assessment of microplastics within the Loire River in the clam Corbicula fluminea exposed to environmentally relevant exposure conditions.

The dispersed pollution caused by microplastics (MPs) represents a current and global concern. While the fragmentation of plastic debris into smaller particles occurs in rivers, little MP research is done on freshwater species and is published compared to the marine environment. The Loire River is the longest river in France and is subject to moderate to high anthropic pressure while it represents major societal and economic issues. However, there are not many studies that have been put forward with regards to the effect of environmental MPs (EMPs) on aquatic organisms and no policies have been enacted to monitor the plastic pollution. In this study, freshwater bivalves, Corbicula fluminea, were exposed for 21 days to environmentally relevant concentrations of a mixture of <200 µm MPs generated from plastic litter collected directly along the banks of the Loire River. This mixture was composed of 40% polyethylene (PE), 40% polypropylene (PP), 10% polyethylene terephthalate (PET) and 10% polyvinylchloride (PVC) (mass percentage). Ecotoxicological effects were assessed from the individual to the molecular levels on several endpoints: condition index, filtration efficiency, enzyme activities, lipid peroxidation, energy reserves and gene expression. The ingestion of EMPs caused damages at the biochemical level. Indeed, we reported an increase in catalase activity in gills and digestive mass, a decrease in TBARs in gills, a decrease in acetylcholinesterase activity in the digestive mass, a decrease of glycogen and lipid contents in the whole organisms and a significant induction of the expression of gst, cat, mp, acp genes. The current results suggest therefore that long-term exposure to realistic doses of EMPs causes toxicity towards freshwater benthic biota. The analysis of biomarker activities and the analysis of gene expression are complementary to prevent the effects of a plastic contamination at higher biological levels in aquatic organisms.

Microplastics in sediments from urban and suburban rivers: Influence of sediment properties.

Although sediments are considered to be a major sink for microplastics (MP), there is still a relative lack of knowledge on the factors that influence the occurrence and abundance of MP in riverine sediments. The present study investigated the occurrence and distribution of MP in riverine sediments collected at twelve sites representative of different populated and urbanized rivers (To Lich, Nhue and Day Rivers) located in the Red River Delta (RRD, Vietnam, during dry and rainy seasons. MP concentrations ranged from 1600 items kg-1 dw to 94,300 items kg-1dw. Fiber shape dominated and MP were made of polypropylene (PP) and polyethylene (PE) predominantly. An absence of seasonal effect was observed for both fragments and fibers for each rivers. Decreasing MP concentrations trend was evidenced from the To Lich River, to the Nhue River and to the Day River, coupled with a decreasing fiber length and an increasing fragment area in the surface sediment from upstream to downstream. Content of organic matter was correlated to MP concentrations suggesting that, high levels of organic matter could be MP hotspots in urban rivers. Also, high population density as well as in highly residential areas are related to higher MP concentrations in sediments. Finally, a MP high ecological risk (RI: 866 to 4711) was calculated in the RDD.

Assessment of microplastic contamination in the Loire River (France) throughout analysis of different biotic and abiotic freshwater matrices.

The contamination of microplastics (MP) in freshwater environments represent a major way for the MP transport in the environment. The assessment of MP pollution in freshwater compartments is then important to visualize the pressure and the impacts on medium, and to set up necessary measures. In this context, this study focused on the influence of anthropogenic activities of a medium French city (Angers) on MP levels in samples collected from the Loire River, the longest river in France. Abiotic and biotic matrices were collected upstream and downstream Angers. A first analysis was performed based on microscopy to determine the size, colour and shape of suspected MP and a complementary analysis by µ-FTIR (micro-Fourier Transform InfraRed) was conducted to determine the composition of plastic particles. Three organisms belonging to different trophic levels were studied: when the MP level was expressed per individual, the lowest abundance of MP was found in Tubifex sp. Followed by Corbicula fluminea, while the highest was measured in Anguilla anguilla. To establish the relationship with their habitat, the presence of MP in sediment and water was also analysed. Therefore, this works constitutes a complete overview of the MP levels in freshwater abiotic and biotic matrices. Overall, the presence of MP in analysed samples did not follow a particular pattern, neither in the sites nor matrices: the characteristics depending on a multifactorial outcome (feeding mode, organism size …). However, correlation of MP pattern between clams and sediment was quite evident, while the one between worms and their habitat was not. This demonstrates the relevance of investigating plastic contamination both in biotic and abiotic matrices. Finally, a standardisation of sampling and analytical analysis protocols would be helpful to make comparisons between studies more robust.

Non-persistent chemicals in polymer and non-polymer products can cause persistent environmental contamination: evidence with DEHP in Europe.

Bis(2-ethylhexyl) phthalate (DEHP) is a plasticizer that has been massively used since the second part of the twentieth century by the plastic industry to provide softness properties to PVC. This chemical is considered as toxic to reproduction and endocrine disrupting, and a wide range of uses are now forbidden by the EU. Despite these regulations, DEHP is still found to be a widespread contaminant in watersheds in the EU. In this study, we calculate retrospective and prospective scenarios of past and future emissions of DEHP in the environment (water, soil, air) in the EU 28, taking into account the entire lifecycle of the substance, from its production and its inclusion in polymer (mainly PVC) and non-polymer products (adhesive and sealant, ceramic and printing ink) to the recycling and end of life of these products. We develop a stock and flow model based on dynamically estimating the stocks of DEHP present in products on the market. Our results show that the introduction of recent regulations to limit the use of DEHP (that bring a 70% reduction of DEHP contained in products placed on the market in 2020 and 75% in 2040) will not reduce significantly future emissions. This persistence of emissions is explained by the high stocks built in the economy and the long-term presence of soft PVC waste in landfills. Our results suggest that DEHP will remain a cause of environmental contamination many decades after uses have declined and even ceased, and it appears to be too late for market regulation at the market stage to offset the effect of past stock buildup and landfilling. It is likely that several chemicals that are not considered as persistent and therefore not the focus of international regulations could exhibit the same characteristics. Regulations should avoid possible use patterns that make hazardous chemicals persistent in products, because they have the potential to create long-term and almost irreversible environmental pollution and impacts.

Macrolitter dataset from a highly frequented roadway in Nantes, France.

Land-based sources of riverine macrolitter are now recognized as a major concern, but few field data on litter amount, composition and sources are available. This is especially the case for macrolitter hotspots like high frequented roadways that could generate large amount of macrolitter potentially reaching rivers. This dataset provides macrolitter amount and composition over one year from a retention pond collecting stormwater and carried macrolitter from a 800 m portion of a highly frequented roadway (around 90,000 vehicles per day). The typology of macrolitter was defined using the TSG-ML/OSPAR classifications. A total of 36,439 items in which 84% of plastics were individually counted, classified and weighted by category for a total mass of 88.5 kg (60% of plastics). Raw data are available in Mendeley Data (DOI:10.17632/t6ryv6crjd.4). Top 10 items represent 92% by count of the total with plastic fragments (31%), cigarette butts (18%), EPS fragments (17%) or foam packaging (11%) as most common items. Top 10 items represent 72% by mass of the total with plastic fragments (24%) and Cardboard (13%) as most common items, followed by foam packaging (6%), wood fragments (6%), industrial plastic sheets (5%), rubber fragments (4%) and EPS fragments (4%). More than 94% of plastic items are below 1.9 g/item. This dataset is related to the research paper Amount, composition and sources of macrolitter from a highly frequented roadway.

Microplastic and microfiber fluxes in the Seine River: Flood events versus dry periods.

Studies on the influence of hydrodynamic conditions on anthropogenic microfiber (MF) and microplastic (MP) distributions in freshwater environments are sparse. In this study, we evaluated the influence of urbanisation gradient on the spatial variability of MFs and MPs. Temporal variability was also assessed by comparing the concentrations and fluxes of MFs and MPs under low flow conditions with those during the January-February 2018 flood event. For each period, Seine river water was collected upstream and downstream of Greater Paris and filtered through an 80 µm net at three different sampling sites. MFs were counted using a stereomicroscope, while MPs were analysed using micro-Fourier transform infrared spectroscopy coupled with siMPle analysis software. The highest concentrations of MFs and MPs were reported at the furthest downstream sites during both periods. However, high water flowrates and urbanisation gradient did not significantly impact MF and MP concentrations, sizes, or polymer distributions. The median MF and MP concentrations were 2.6 and 15.5 items/L and their interquartile ranges were 1.6 and 4.9 items/L (n = 10), respectively, illustrating relatively stable concentrations in spite of the urbanisation gradient and variations in the flowrate. In contrast to the concentration, size, and polymer distribution characteristics, MP mass fluxes were strongly affected by river flow. MF and MP fluxes show increases in the number and mass of particles from upstream to downstream. The downstream site presents high MP mass fluxes, which range between 924 and 1675 tonnes/year. These results may indicate significant MP inputs from the Paris Megacity through wastewater treatment plant effluents and untreated stormwater. The January-February 2018 flood event, which represented 14.5% of the year (in terms of time), contributed 40% of the yearly MP mass fluxes. Thus, flood events contribute strongly to MP fluxes.

Microplastics and microfibers in urban runoff from a suburban catchment of Greater Paris.

Microplastics (MPs) and microfibers (MFs) in stormwater have been poorly investigated. Data on their intra and inter rain events variability over time are still sparse. For the first time, the variability of microlitter concentrations in stormwater has been studied. MF and MP concentrations were investigated in stormwater runoff at the outlet of the suburban catchment at Sucy-en-Brie (a suburb of Paris, France), during four rain events. Median MF and MP concentrations were 1.9 and 29 items/L, with an interquartile range of 2.3 and 36 items/L, respectively (N = 18). A different pattern was observed between MFs and MPs. While no relationship or trends were observed for MFs, the highest MP concentrations were observed before the flow rate peak of the rain events. This could indicate a difference in the behaviour between MFs and MPs. We estimated the median MP mass concentration to be 56 µg/L with an interquartile range of 194 µg/L, whereas the mass concentration of macroplastics was estimated to be 31 µg/L with an interquartile range of 22 µg/L at the same sampling site, in a previous study. For this sampling site, MPs and macroplastics have the same order of magnitude. This study may have strong implications on microplastic assessment in urban waters.

A microfluidic chip enables fast analysis of water microplastics by optical spectroscopy.

Microplastics contaminating drinking water is a growing issue that has been the focus of a few recent studies, where a major bottleneck is the time-consuming analysis. In this work, a micro-optofluidic platform is proposed for fast quantification of microplastic particles, the identification of their chemical nature and size, especially in the 1-100 µm size range. Micro-reservoirs ahead of micro-filters are designed to accumulate all trapped solid particles in an ultra-compact area, which enables fast imaging and optical spectroscopy to determine the plastic nature and type. Furthermore, passive size sorting is implemented for splitting the particles according to their size range in different reservoirs. Besides, flow cytometry is used as a reference method for retrieving the size distribution of samples, where chemical nature information is lost. The proof of concept of the micro-optofluidic platform is validated using model samples where standard plastic particles of different size and chemical nature are mixed.

Abundance, composition and fluxes of plastic debris and other macrolitter in urban runoff in a suburban catchment of Greater Paris.

Stormwater possibly represents a significant input for plastic debris in the environment; however, the quantification and composition of plastic debris and other macrolitter in stormwater are not available in literature and the amounts discharged into freshwater have been poorly investigated. To obtain a better understanding, the occurrence, abundance, and composition of the macrolitter in screened materials from stormwater were investigated at a small residential suburban catchment (Sucy-en-Brie, France) in Greater Paris. The macrolitter, particularly the plastic debris, was sorted, weighed, and classified based on the OSPAR methodology. On average, plastics accounted for at least 62% in number and for 53% of the mass of all the anthropogenic waste found in the screened materials. The most common items were plastic bags or films, crisp or sweet packets, cigarette butts, plastic fragments of unknown origin, garbage bags or garbage bag strings, foil wrappers, tampon applicators, plastic cups, and medical items such as bandages. Plastic debris concentrations in runoff water ranged between 7 and 134 mg/m3 (i.e. 0.4-1.7 kg.yr-1.ha-1 or 4.8-18.8 g.yr-1.cap-1). When extrapolated to the Greater Paris area, the estimated amount of plastic debris discarded into the environment through untreated stormwater of separate sewer systems ranges from 8 to 33 tons.yr-1.

Fluorescence excitation/emission matrices as a tool to monitor the removal of organic micropollutants from wastewater effluents by adsorption onto activated carbon.

Monitoring the removal of organic micropollutants (OMPs) in advanced wastewater treatment facilities requires expensive and time-consuming analytical methods that cannot be installed online. Spectroscopic techniques such as fluorescence excitation/emission spectroscopy were demonstrated to offer the potential for monitoring OMPs removal in conventional wastewater treatment plants or ozonation pilots but their application to activated carbon (AC) adsorption processes was only investigated at lab scale and not in real treatment facilities. In this study, indexes from fluorescence emission/excitation matrices (EEMs) were used to find correlations with the removal of 28 OMPs from a large-scale AC pilot in fluidized bed employed for wastewater advanced treatment, as well as from batch experiments. Differences in OMPs removal could be observed depending on the operational conditions (i.e. pilot or batch experiments, contact time, type of AC) and the physico-chemical properties of the molecules. 7 PARAFAC components were derived from the fluorescence EEMs of 60 samples obtained before and after adsorption. Positive correlations were obtained between the removal of fluorescence indexes and most OMPs, and correlation coefficients were much higher than the ones obtained with UV254, confirming the interesting potential of fluorescence spectroscopy to accurately monitor adsorption performances at the industrial scale. The highest correlation coefficients were obtained for OMPs having the best removals while the ones that were refractory to adsorption, as well as to interactions with DOM, exhibited weak correlations. These results suggest that interactions between OMPs and fluorescing DOM and their subsequent co-adsorption onto AC were at the origin of the correlations found. Lower correlations were also found for the most biodegradable OMPs, which indicated that the occurrence of biological effects could make the monitoring of these compounds more challenging.

Impacts of organic matter digestion protocols on synthetic, artificial and natural raw fibers.

As microplastic studies grow, environmental concerns of all kinds of fibers are currently investigated. However, there is a gap in data regarding the impacts of digestion protocols on fibers integrity. This work focuses on the impact of five commonly used digestion protocols on the seven most produced fibers in traditional textile: three synthetics (polyamide 6.6 (PA 6.6), polyethylene terephthalate (PET) and polyacrylonitrile (acrylic)), one artificial (viscose), two vegetal natural (cotton and flax) and one animal natural (wool). The protocols to be tested were selected based on the literature: 10% KOH at 40 °C for 24 h; 10% KOH at 60 °C for 24 h; diluted NaClO at room temperature (~20 °C) for 15 h; 30% H2O2 at 40 °C for 48 h; Fenton's reagent with 30% H2O2 for 2 h at room temperature (~20 °C). The fibers were characterized before and after digestion. The effects of those protocols on fibers integrity have been assessed using several of their performance parameters. High degradations were observed for PET with 10% KOH 60 °C whereas almost no impact was observed at 40 °C. H2O2 digestion affects mechanical properties of different fibers, particularly PA 6.6. Both protocols should be avoided for synthetic fibers analyses. NaClO digestion mainly affected flax and viscose. Diluted NaClO at room temperature for 15 h, 10% KOH at 40 °C for 24 h and Fenton's reagent are more appropriate to maintain fibers integrity.

A first estimation of uncertainties related to microplastic sampling in rivers.

Many studies have been conducted to quantify microplastic contamination, but only a few of them have actually the sampling methodology and associated uncertainties. This study seeks to examine the influence of sampling strategy on the confidence interval of river microplastic estimates. 16 samples are collected in the Gave de Pau River (southwestern France) during a three-hour window with a 330-µm mesh size net. Three different exposure times (3, 5 and 7 min) allow for a respective filtration rate by the net of 35.6 m3 (3 samples), 59.4 m3 (10 samples), and 83.2 m3 (3 samples) of water. Organic matter contained in samples is removed by hydrogen peroxide oxidation. The plastic particles are then counted and classified under a binocular microscope. The microplastic concentrations vary between 2.64 and 4.24 microplastics/m3, with a median value of 3.26 microplastics/m3. Statistical analysis does not show differences in microplastic concentrations for the three exposure times. This result seems to demonstrate that a filtration of approx. 35 m3 of water is sufficient under similar conditions (similar flow condition and degree of microplastic contamination) and can help reduce sampling and sample processing time. Other analyses, based on 10 filtrations of 59.4 m3, show that the higher the number of samples, the lower the confidence interval. For triplicates, the mean confidence interval reaches 15% of the median value. Thus, collecting triplicates would seem to offer a reasonable optimum, in combining an acceptable error percentage and time efficiency. These results might depend on the microplastic load of the river, therefore making it necessary to conduct similar analyses on other rivers. This study reports for the first time uncertainties related to microplastic sampling in rivers. Such findings will serve to set up long term monitoring, highlight spatial differences between sites and improve the accuracy of annual microplastic fluxes in rivers.

Influence of dissolved organic matter on the removal of 12 organic micropollutants from wastewater effluent by powdered activated carbon adsorption.

The presence of dissolved organic matter (DOM) in wastewater effluents is recognized as the main factor limiting the adsorption of organic micropollutants (OMPs) onto activated carbon. The degree of the negative effect that DOM, depending on its quality, exerts on OMPs adsorption is still unclear. The influence of the interactions between DOM and OMPs on their removal is also not fully understood. Adsorption isotherms and conventional batch tests were performed in ultra-pure water and in wastewater effluent to study the influence of DOM on the adsorption of 12 OMPs onto powdered activated carbon. Best fit of adsorption pseudo-isotherms was obtained with the Freundlich equation and showed, as expected, that OMPs adsorption was higher in ultra-pure water than in wastewater effluent due to the presence of DOM leading to pore blockage and competition for adsorption sites. LC-OCD analysis revealed that biopolymers and hydrophobic molecules were the most adsorbed fractions while humic acids were not removed after a contact time of either 30 min or 72 h. The presence of DOM had a negative impact on the removal of all OMPs after 30 min of adsorption, but similar removals to ultra-pure water were obtained for 6 OMPs after 72 h of adsorption. This demonstrated that competition between DOM and OMPs for adsorption sites was not a major mechanism as compared to pore blockage, which only slowed down the adsorption and did not prevent it. The charge of OMPs had a clear impact: the adsorption of negatively charged compounds was reduced in the presence of wastewater effluent due to repulsive electrostatic interactions with the adsorbed DOM and the PAC surface. On the other hand, the removal of positively charged compounds was improved. A 24 h pre-equilibrium between OMPs and DOM improved their removal onto PAC, which suggest that OMPs and DOM interacted in solution which decreased the negative effects caused by the presence of DOM, e.g. through co-adsorption of an OMP-DOM complex.

Temporal dynamic of anthropogenic fibers in a tropical river-estuarine system.

Anthropogenic fibers, gathering synthetic fibers, artificial fibers and natural fibers are ubiquitous in the natural environment. Tremendous concentrations of anthropogenic fibers were previously measured in the tropical Saigon River (Vietnam), i.e. a river impacted by textile and apparel industries. In the present study, we want to examine the role of contrasted seasonal variation (e.g., dry and rainy seasons), via the rainfall and monthly water discharges, and of water's physico-chemical conditions on the concentrations of anthropogenic fibers in the surface water. The one year and half monthly survey evidenced that concentrations of anthropogenic fibers varied from 22 to 251 items L-1 and their variations were not related to rainfall, water discharge or abiotic factors. However, their color and length distribution varied monthly suggesting variations in sources and sinks. Based on the 2017 survey, we estimated an annual emission of anthropogenic fibers from the river to the downstream coastal zone of 115-164 × 1012 items yr-1.

Benefits of ozonation before activated carbon adsorption for the removal of organic micropollutants from wastewater effluents.

Advanced processes for the removal of organic micropollutants (OMPs) from wastewater effluents include adsorption onto activated carbon, ozonation, or a combination of both processes. The removal of 28 OMPs present in a real wastewater effluent was studied by ozonation coupled to activated carbon adsorption and compared to a sole adsorption. The influence of the specific ozone dose (0.09-1.29 gO3/gDOC) and the influence of the powdered activated carbon (PAC) dose (2, 5 and 10 mg/L) were first studied separately. OMPs removal increased with both the specific ozone dose (up to 80% for a dose higher than 0.60 gO3/gDOC) and the PAC dose. Ozonation performances decreased in presence of suspended solids, which were converted to dissolved organic carbon. A correction of the specific ozone dose according to the suspended solids levels, in addition to nitrite, should be considered. The influence of ozonation (0.09, 0.22, 0.94 and 1.29 gO3/gDOC) on OMPs adsorption was then assessed. OMPs adsorption didn't change at low specific ozone doses but increased at higher specific ozone doses due to a decrease in DOM adsorption and competition with OMPs. At low ozone doses followed by adsorption (0.22 gO3/gDOC and 10 mg/L PAC), the two processes appeared complementary as OMPs with a low reactivity toward ozone were well absorbed onto PAC while most OMPs refractory to adsorption were well eliminated by ozone. Improved removals were obtained for all compounds with these selected doses, reaching more than 80% removal for most OMPs while limiting the formation of bromate ion.

Influence of the properties of 7 micro-grain activated carbons on organic micropollutants removal from wastewater effluent.

Most studies dedicated to organic micropollutants (OMPs) removal from wastewater effluents by adsorption onto activated carbon (AC) only consider a few conventional AC properties. The link between OMPs removal and these properties is often missing, which limits the understanding of the adsorption process and the interpretation of the results. The chemical, physical and textural properties of seven newly commercialized micro-grain activated carbons (µGACs) were determined to assess their influence on the removal of 28 OMPs. Conventional batch tests with wastewater effluent showed that a high percentage of microporous volume (>65%) was detrimental for the removal of 10 OMPs, probably due to a higher blockage of micropores by dissolved organic matter (DOM). The removal of 5 OMPs was correlated with µGACs surface chemistry properties (i.e. charge) which were potentially modified by DOM adsorption or inorganic species, thus favoring the adsorption of positively-charged compounds. A combination of OMPs properties including their charge, hydrophobicity and minimal projection area could explain their removal. Correlations were found between the removal of several OMPs and UV254, suggesting that DOM and OMPs interacted with each other or followed similar adsorption mechanisms. A decrease in µGACs particle size had a positive impact on UV254 removal under continuous-flow conditions in columns representative of a large-scale pilot due to better expansion.