Effects and bioaccumulation of Cr(III), Cr(VI) and their mixture in the freshwater mussel Corbicula fluminea

Chromium has two main oxidation states, Cr(III) and Cr(VI), that can occur simultaneously in natural waters. Current consensus holds that Cr(VI) is of high ecotoxicological concern, but regards Cr(III) as poorly bioavailable and relatively non-toxic. In this work, the effects and bioaccumulation of Cr(III), Cr(VI) and their mixture were studied using the freshwater clam Corbicula fluminea as a model organism. Mixture exposures were carried out using solutions isotopically enriched in ⁵⁰Cr(III) or ⁵³Cr(VI), allowing to quantify the contribution of each redox form to total Cr accumulation in the clams. Following exposure to individual redox forms, Cr(III) accumulated preferentially in the digestive glands and Cr(VI) in the gills of C. fluminea. In mixture exposures, both redox forms accumulated mainly in the gills; the concentration of Cr(III) in the digestive glands being much lowered compared with individual exposures. Both oxidation states affected the expression of biomarkers related to energy reserves, cellular damage and mitochondrial functioning, as well as the expression of mRNA for detoxification genes. The observed effects differed between gills and digestive glands. The present study suggests that Cr(III) is a bioavailable and biologically active elemental species deserving more consideration by the ecotoxicological community.

Electrosorption of phenolic compounds from olive mill wastewater: Mass transport consideration under a transient regime through an alginate-activated carbon fixed-bed electrode

Olive mill wastewater (OMWW) is an environmentally critical effluent, specifically due to its high content of phenolic compounds (PCs), which are hazardous due to their antimicrobial activities in water. However, their properties have good health effects at suitable doses. For the first time, the electrosorption of PCs from actual OMWW has been proposed for their possible recovery as value-added compounds, while decontaminating OMWW. A bio-sourced alginate-activated carbon (AC) fixed-bed electrode was prepared based on the reuse of olive pomace solid waste as powdered AC. At the optimal AC content (1% w/v), the internal ohmic drop voltage was lower (2.26 V) and the mass transport coefficient was higher (9.7 10^-5 m s^-1) along with the diffusivity (7.3 10^-9 m² s^-1), which led to enhanced electrosorption rates. Afterward, an optimal electrode potential was obtained (-1.1 V vs. Ag/AgCl), while higher voltages led to faradaic reactions. Moreover, the adsorption capacity was lower (123 mg g^-1) than that of electrosorption (170 mg g^-1) and was even higher (307 mg g^-1) with actual effluents. This was probably due to the influence of electromigration, which was confirmed by new models that could predict the electrosorption kinetics well considering mass transport and acid dissociation constants.

A critical review on the electrosorption of organic compounds in aqueous effluent - Influencing factors and engineering considerations

Despite being an old process from the end of the 19^th century, electrosorption has attracted renewed attention in recent years because of its unique properties and advantages compared to other separation technologies and due to the concomitant development of new porous electrode materials. Electrosorption offer the advantage to separate the pollutants from wastewater with the possibility of selectively adsorbing and desorbing the targeted compounds. A comprehensive review of electrosorption is provided with particular attention given to the electrosorption of organic compounds, unlike existing capacitive deionization review papers that only focus on inorganic salts. The background and principle of electrosorption are first presented, while the influence of the main parameters (e.g., electrode materials, electrode potential, physico-chemistry of the electrolyte solutions, type of compounds, co-sorption effect, reactor design, etc.) is then detailed and the modeling and engineering aspects are discussed. Finally, the main output and future prospects about recovery studies and combination between electro-sorption/desorption and degradation processes are given. This review particularly highlights that carbon-based materials have been mostly employed (85% of studies) as porous electrode in organics electrosorption, while existing studies lack of electrode stability and durability tests in real conditions. These electrodes have been implemented in a fixed-bed reactor design most of the time (43% of studies) due to enhanced mass transport. Moreover, the electrode potential is a major criterion: it should be applied in the non-faradaic domain otherwise unwanted reactions can easily occur, especially the corrosion of carbon from 0.21 V/standard hydrogen electrode or the water oxidation/reduction. Furthermore, there is lack of studies performed with actual effluents and without addition of supporting electrolyte, which is crucial for testing the real efficiency of the process. The associated predictive model will be required by considering the matrix effect along with transport phenomena and physico-chemical characteristics of targeted organic compounds.

Performance and dynamic modeling of a continuously operated pomace olive packed bed for olive mill wastewater treatment and phenol recovery

The solid waste of olive oil extraction processes (olive pomace, OP) was converted into activated carbon (AC) by treating it with NaOH and then encapsulating it within sodium alginate (SA) in beads by crosslinking (SA-AC beads). The prepared SA-AC beads were utilized as an adsorbent for the elimination and recovery of phenolic compounds (PCs) from olive mill wastewater (OMWW) following a zero liquid and waste discharge approach to implement and promote the circular economy concept. The novel AC and SA-AC beads were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and Brunauer, Emmett and Teller (BET) analysis. The adsorption performance of these beads was evaluated in batch and fixed-bed reactors operated in a concurrent flow system. The results revealed that an adsorption capacity of 68 mg g^-1 was attained for 4000 mg L^-1 phenolic compounds. The kinetics of the adsorption process of the PCs fit a pseudo second-order model, and the most likely mechanism took place in two stages. The adsorption isotherm conformed to the Langmuir model, representing the monolayer adsorption of the phenolic compounds. The dynamic models were used, and they accurately represented the breakthrough curves. Considering PC recovery and process reusability, a regeneration experiment of SA-AC beads was carried out in fixed-bed reactors. SA-AC beads showed a high percentage desorption >40% using ethanol and were efficient after several cycles of OMWW treatment and phenol recovery.

The potential of Blepharidium guatemalense for nickel agromining in Mexico and Central America

The aim of this study was to assess the potential of the woody nickel hyperaccumulator species Blepharidium guatemalense (Standl.) Standl. for agromining in southeastern Mexico. Pot trials consisting of nickel dosing (0, 20, 50, 100, and 250 mg Ni kg^-1), and synthetic and organic fertilization were conducted. Field trials were also undertaken with different harvesting regimes of B. guatemalense. Foliar nickel concentrations increased significantly with rising nickel additions, with a 300-fold increase at 250 mg Ni kg^-1 treatment relative to the control. Synthetic fertilization strongly increased nickel uptake without any change in plant growth or biomass, whereas organic fertilization enhanced plant shoot biomass with a negligible effect on foliar nickel concentrations. A 5-year-old stand which was subsequently harvested twice per year produced the maximum nickel yield tree^-1yr^-1, with an estimated total nickel yield of 142 kg ha^-1yr^-1. Blepharidium guatemalense is a prime candidate for nickel agromining on account of its high foliar Ni concentrations, high bioconcentration (180) and translocation factors (3.3), fast growth rate and high shoot biomass production. Future studies are needed to test the outcomes of the pot trials in the field. Extensive geochemical studies are needed to identify potential viable agromining locations. Novelty Statement Our research team is a pioneer in the discovery of metal hyperaccumulator plants in Mesoamerica with at least 13 species discovered in the last 2 years. This study is the first to assess the potential of nickel agromining (phytomining) in Mexico (and in all the American continent), using one of the strongest nickel hyperaccumulators reported so far. The promising results of this study are the basis for optimal agricultural management of Blepharidium guatemalense.

Effect of lockdown on wastewater characteristics: a comparison of two large urban areas

The effect of the lockdown imposed to limit the spread of SARS-CoV-2 in France between March 14 and May 11, 2020 on the wastewater characteristics of two large urban areas (with between 250,000 and 300,000 inhabitants) was studied. The number of outward and inward daily commuters was extracted from national census databases related to the population and their commuting habits. For urban area A, with the larger number of daily inward commuters (110,000, compared to 53,000 for B), lockdown was observed to have an effect on the monthly load averages of chemical oxygen demand, biochemical oxygen demand, total Kjeldahl nitrogen, total suspended solids and total phosphorus, all of which decreased (confidence level of 95%). This decrease, which varied between 20% and 40% and reached 45% for COD, can be related to the cessation of catering and activities such as hairdressing, which generate large amounts of graywater. The ammonium loads, due to the use of toilets before leaving for work and after returning from work, remained constant. In the case of urban area B, lockdown had no noticeable effect. More data would be necessary in the long term to analyze the effect of changes in the balance between ammonia and carbon sources on the operation of wastewater treatment plants.

Understanding Rare Earth Elements concentrations, anomalies and fluxes at the river basin scale: The Moselle River (France) as a case study

Anthropogenic activities linked to various new technologies are increasingly disrupting REEs biogeochemical cycles. A catchment-based perspective is therefore necessary to distinguish between natural (i.e., changes in lithology) and human-related sources of REEs variability. In the present study, REEs patterns, anomalies and fluxes were investigated in the French part of the Moselle River basin (Moselle River itself and some of its headstreams and tributaries). The REEs patterns in the headstream waters were highly variable and mostly related to the complex underlying lithology (granite, sandstone, tuff and graywacke). Along the Moselle River, the presence of positive Gd anomalies and a regular LREEs depletion/HREEs enrichment pattern on sandstone/limestone substrates were the most distinctive features. The Gd anomaly varied from 1.8 to 8.7, with anthropogenic Gd representing 45 to 88% of the total Gd. A linear relationship was obtained between the anthropogenic Gd flux and the cumulative population along the watershed. However, the magnitude of the Gd anomalies was shown to depend on the methodological approach chosen for their calculation. The use of a threshold value to identify the presence of an anthropogenic Gd anomaly may therefore be basin (and lithology) dependent, and care has to be taken in comparing results from different rivers or lithologies. Concentration of anthropogenic Gd in the Moselle River and its tributaries were close to, or above, the value of 20 ng/L reported in literature to elicit adverse biological effects in laboratory cell cultures. The ecotoxicological significance of Gd anomalies deserves further investigation because concentrations of anthropogenic Gd may also vary depending on the methodological approach used for calculating Gd anomalies.

A global multinational survey of cefotaxime-resistant coliforms in urban wastewater treatment plants

The World Health Organization Global Action Plan recommends integrated surveillance programs as crucial strategies for monitoring antibiotic resistance. Although several national surveillance programs are in place for clinical and veterinary settings, no such schemes exist for monitoring antibiotic-resistant bacteria in the environment. In this transnational study, we developed, validated, and tested a low-cost surveillance and easy to implement approach to evaluate antibiotic resistance in wastewater treatment plants (WWTPs) by targeting cefotaxime-resistant (CTX-R) coliforms as indicators. The rationale for this approach was: i) coliform quantification methods are internationally accepted as indicators of fecal contamination in recreational waters and are therefore routinely applied in analytical labs; ii) CTX-R coliforms are clinically relevant, associated with extended-spectrum β-lactamases (ESBLs), and are rare in pristine environments. We analyzed 57 WWTPs in 22 countries across Europe, Asia, Africa, Australia, and North America. CTX-R coliforms were ubiquitous in raw sewage and their relative abundance varied significantly (<0.1% to 38.3%), being positively correlated (p < 0.001) with regional atmospheric temperatures. Although most WWTPs removed large proportions of CTX-R coliforms, loads over 10³ colony-forming units per mL were occasionally observed in final effluents. We demonstrate that CTX-R coliform monitoring is a feasible and affordable approach to assess wastewater antibiotic resistance status.

Production of electrolytic iron from red mud in alkaline media

In this study, the feasibility of producing electrolytic iron from red muds in a strongly alkaline medium at 110 °C was studied. The red mud samples from a French industry were characterized by various techniques (ICP-AES, SEM, XRD) to determine their chemical and mineralogical compositions. The main phase in the red mud investigated was hematite (α-Fe₂O₃). Iron electrodeposition tests from red mud suspended in a 12.5 mol/L NaOH electrolyte were conducted at constant current in a stirred electrochemical cell. The solid:liquid ratio and amounts of impurities contained in red mud were varied to optimize the faradaic yield and the production rate of electrolytic iron. Whereas hematite can be reduced to iron with a current efficiency over 80% for a current density (cd) up to 1000 A/m², the current efficiency with red muds was highest for a cd below 50 A/m² and then decreased regularly to 20% at 1000 A/m². In all cases, the deposit produced contained more than 97% metal iron. The moderate performance of the process investigated with red mud was attributed to a troublesome adsorption of red mud particles on the cathode, making the reduction far less efficient than that with hematite.

Rare earth elements (REE) in the urban wastewater of Cotonou (Benin, West Africa)

The rare earth element (REE) contamination of urban wastewater, which was collected from open sewers and the inlet of a wastewater treatment plant in Cotonou (Benin), was assessed. The drinking water distributed to the inhabitants of Cotonou and water samples from private wells were also analyzed. The sampling occurred between October and December 2016 and the samples were analyzed by ICP-MS. Although the only magnetic resonance imaging facility in Cotonou opened in November 2016, pollution by anthropogenic gadolinium (Gd), which is included in phase contrast agents, was observed: there was 30-620 times more Gd in wastewater samples than in drinking and well water samples. Europium was another REE presenting positive anomalies. It is hypothetized than the europium came from the leachates of solid waste piles in the street. In the absence of any wastewater treatment, the REEs found in the wastewater are spread to the aquatic environment. It would be interesting to monitor the wastewater REEs over the long term. So far, the aquifers used for water provision have not been polluted by the anthropogenic REEs.

Electrolytic iron production from alkaline suspensions of solid oxides: compared cases of hematite, iron ore and iron-rich Bayer process residues

Iron can be produced by the direct electrochemical reduction of hematite particles suspended in hot, concentrated NaOH solutions. Because various other iron sources can be considered, the present work was aimed at investigating the electrolytic treatment of the “red mud” generated by the Bayer process for alumina preparation from bauxite. Such sources contain very high amounts of impurities, in particular silicon and aluminium oxide-based minerals, in addition to other mineral phases. Electrolytic reductive treatment of the industrial red mud sample was shown to be possible but with both lower current density and current efficiency than for pure hematite. After deposition tests at a fixed current density, further experiments in simulation tests have been carried out for better understanding. In particular, hematite particles were tested with and without impurities introduced in the solution. Presence of little soluble impurities at the particle surface appear to hinder the reactivity of the suspended particles at the cathode surface, whereas side-hydrogen reaction still occurs. 

Fate of inorganic nitrogen species under homogeneous Fenton combined with electro-oxidation/reduction treatments in synthetic solutions and reclaimed municipal wastewater

The fate of inorganic nitrogen species has been studied for the first time in electro-Fenton (EF) conditions in acid media. A redox cycle is first obtained and validated with a kinetic model in synthetic solution and highlights the removal of nitrite that is quickly oxidized into nitrate while the reduction conditions are sufficient to reduce nitrate into ammonium cation. However, NH₄⁺ and gaseous nitrogen accumulate in such solution. The study in reclaimed municipal wastewater emphasize the removal of NH₄⁺ with formation of chloramines in the presence of initial chloride ions, a species widely present in wastewater effluent. Contrastingly, NO₃^- remain constant all along the electrolysis even after 2.1 Ah L^-1. The oxidation conditions were not sufficient to produce perchlorate while chlorate accumulated in solution. Therefore, it limits the use of EF for direct use for drinking water purpose but could be considered as complementary treatment for wastewater reuse applications.

Population mobility and urban wastewater dynamics

Dynamic influent models, which have been proposed to test control strategies using virtual wastewater treatment plants, should be as realistic as possible. The number of inhabitants in the catchment at any given time and their ways of life are among the parameters affecting the quality of these models. Census data related to work and school commutes were used to evaluate the number of people present in a given urban area. Based on the example of a large urban catchment (Grand Nancy, France), the results show that a population increase of 30% could occur during working hours resulting from the imbalance between workers leaving and coming into the catchment. Combined with information related to the local way of life, variation in the population helps to explain changes in wastewater flow rate and pollution (carbon, nitrogen, phosphorus and heavy metals), which present several maxima reflecting daily activities, such as bladder voiding, meals, the use of washrooms, etc. However, no well-defined variation patterns for pH and conductivity, which are linked to the concentrations of anions and cations in the wastewater, were observed. Slight reductions (up to 10% on Sundays) in the flow and pollution load were observed on weekends as the commuter flow decreased. Census data proved to be efficient in helping to understand the daily pattern of urban wastewater characteristics.

Characterization by fluorescence of dissolved organic matter in rural drinking water storage tanks in Morocco

Water storage tanks, fed directly from the river through opened channels, are particular systems used for water supply in rural areas in Morocco. The stored water is used as drinking water by the surrounding population without any treatment. UV-visible spectroscopy and fluorescence spectroscopy (excitation-emission matrices and synchronous fluorescence) have been tested as rapid methods to assess the quality of the water stored in the reservoirs as well as along the river feeding them. Synchronous fluorescence spectra (SFS50), collected with a difference of 50 nm between excitation and emission wavelengths, revealed a high tryptophan-like fluorescence, indicative of a pollution induced by untreated domestic and/or farm wastewater. The best correlations were obtained between the total SFS50 fluorescence and dissolved organic carbon (DOC) and biological oxygen demand, showing that the contribution of humic-like fluorescent substances cannot be neglected to rapidly assess reservoir water quality in terms of DOC by fluorescence spectroscopy.

Vancomycin sorption on activated sludge Gram+ bacteria rather than on EPS; 3D Confocal Laser Scanning Microscopy time-lapse imaging

Antibiotics-bacteria interactions depend on antibiotic concentration at the scale of bacteria. This study investigates how vancomycin penetrates into activated sludge flocs and can be sorbed on the bacteria and extracellular polymeric substances (EPS). The 3D structure of flocs was imaged using EPS autofluorescence. The green fluorescent BODIPY^® FL vancomycin was introduced in a microscopic chamber containing activated sludge and penetration of vancomycin into the flocs by diffusion was observed using time-lapse microscopy. The penetration depended on the floc structure, as long and large pores could go through the whole flocs making preferential path. The antibiotic concentration into the flocs was also found to depend on the sorption rate. BODIPY^® FL vancomycin was found to bind preferentially into Gram⁺ bacteria than on EPS. The vancomycin adsorption constant on bacteria according to the linear adsorption model, Kd_bacteria was estimated to be 5 times higher (SD 2.6) than the adsorption constant on EPS Kd_EPS. These results suggest that antibiotic removal by sorption into wastewater treatment plants could change according to the amount of bacteria in the sludge. Moreover, antibiotic concentration at the scale of bacteria could be significantly higher than the concentration in the bulk solution and this should be taken into account when studying antibiotic activity or biodegradation.

Assessment of organic pollution of an industrial river by synchronous fluorescence and UV-vis spectroscopy: the Fensch River (NE France)

To rapidly monitor the surface water quality in terms of organic pollution of an industrial river undergoing restoration, optical methods (UV-visible spectrometry and fluorescence) were applied in parallel to classical physical-chemical analyses. UV-visible spectra were analyzed using the maximum of the second derivative at 225 nm (related to nitrates), specific absorbance at 254 nm (SUVA₂₅₄), and the spectral slope between 275 and 295 nm (S _275-295) (related to the aromaticity and molecular weight of dissolved organic carbon). The synchronous fluorescence spectra (wavelength difference = 50 nm) exhibited a high variability in the composition of dissolved organic material between the upstream and downstream sections and also versus time. The principal components analysis of the entire set of synchronous fluorescence spectra helped to define three river sections with different pollution characteristics. Spectral decomposition was applied to the two most upstream sections: five fluorophores, classical in rivers impacted by domestic sewage and related to protein-like (λ _ex = 280 nm) and humic-like fluorescence (M-type with λ _ex ≈ 305-310 nm and C-type with λ _ex ≥ 335 nm), were identified. The irregular shape of the synchronous fluorescence spectra in the most downstream section is likely due to organic pollutants of industrial origin; however, their variability and the complexity of the spectra did not allow the further elucidation of their nature.

Chronic impact of sulfamethoxazole on the metabolic activity and composition of enriched nitrifying microbial culture

This study investigated the chronic impact of sulfamethoxazole (SMX) on activated sludge sustaining an enriched nitrifying biomass. For this purpose, a laboratory scale fill and draw reactor was operated with 100 mg COD/L of peptone mixture and 50 mg N/L of ammonia at a sludge age of 15 days. Additionally, the biomass was exposed to a daily SMX dose of 50 mg/L once the reactor reached steady-state conditions. The reactor performance and microbial composition were monitored for 37 days with conventional parameters and molecular techniques based on the gene for ammonia monooxygenase subunit A (amoA) and the prokaryotic 16S rRNA gene. Denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene cloning analyses suggested a microbial community change concurrent with the addition of SMX. Specifically, quantitative polymerase chain reaction analyses (qPCR/RT-qPCR) revealed a significant reduction in the levels and activity of ammonia oxidizing bacteria (AOB). However, the acclimation period ended with high amoA mRNA levels and improved nitrification efficiency. Partial degradation of SMX by heterotrophic bacteria was also observed.

Spectrophotometric characterization of dissolved organic matter in a rural watershed: the Madon River (N-E France)

In the last 20 years, increasing dissolved organic carbon (DOC) concentrations have been observed in several rivers and lakes in Europe. This increase has reduced the quality of the aquatic environment. In this study, UV-vis spectroscopy and synchronous fluorescence spectroscopy with a difference of 50 nm between the excitation and emission (SF50) were used to characterize the DOC in a rural river (Madon River). The specific absorbance index at 254 nm (SUVA254) which is related to the aromaticity of DOC was extracted from UV-vis spectra, whose maximum of the second derivative (occurring near 225 nm) is related to nitrates. SF50 spectra which are characterized by well-defined peaks indicated large spatial and temporal variations. Two methods were used to analyze and compare these spectra. The first method was based on the decomposition of the SF50 spectra into four Gauss functions: B1 (related to tryptophan-like fluorescence), B2 and B3 (related to humic substances), and B4 (related to chlorophyll-like substances). The second method was principal components analysis (PCA), which results yielded three principal components that accounted for 95% of the variance. Although PCA enables the consideration of the spectra without making assumptions regarding the number of fluorophores, the results from the decomposition in Gauss function were easier to interpret.

Chronic impact of tetracycline on nitrification kinetics and the activity of enriched nitrifying microbial culture

This study evaluated the chronic impact of tetracycline on biomass with enriched nitrifying community sustained in a lab-scale activated sludge system. For this purpose, a fill and draw reactor fed with 100 mg COD/L of peptone mixture and 50 mg N/L of ammonia was sustained at a sludge age of 15 days. At steady-state, the reactor operation was continued with a daily tetracycline dosing of 50 mg/L for more than 40 days, with periodic monitoring of the microbial composition, the nitrifying bacteria abundance, as well as the amoA and 16S rRNA gene activity, using molecular techniques. Changes in the kinetics of nitrification were quantified by modelling concentration profiles of major nitrogen fractions and oxygen uptake rate profiles derived from parallel batch experiments. Activated sludge modeling results indicated inhibitory impact of tetracycline on the growth of nitrifiers with a significant increase of the half saturation coefficients in corresponding rate equations. Tetracycline also inactivated biomass components of the enriched culture at a gradually increasing rate with time of exposure, leading to total collapse of nitrification. Molecular analyses revealed significant changes in the composition of the microbial community throughout the observation period. They also showed that continuous exposure to tetracycline inflicted significant reduction in amoA mRNA and 16S rRNA levels directly affecting nitrification. The chronic impact was much more pronounced on the ammonia oxidizing bacteria (AOB) community. These observations explained the basis of numerical changes identified in the growth kinetics of nitrifiers under stress conditions.

Occurrence of eight household micropollutants in urban wastewater and their fate in a wastewater treatment plant. Statistical evaluation

The occurrence in urban wastewater of eight micropollutants (erythromycin, ibuprofen, 4-nonylphenol (4-NP), ofloxacin, sucralose, triclosan, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)) originating from household activities and their fate in a biological wastewater treatment plant (WWTP) were investigated. Their concentrations were assessed in the liquid and solid phases (sewage particulate matter and wasted activated sludge (WAS)) by liquid chromatography-tandem mass spectrometry. The analysis of sewage from two different urban catchments connected to the WWTP showed a specific use of ofloxacin in the mixed catchment due to the presence of a hospital, and higher concentrations of sucralose in the residential area. The WWTP process removed over 90% of ibuprofen and triclosan from wastewater, while only 25% of ofloxacin was eliminated. Erythromycin, sucralose and PFOA were not removed from wastewater, the influent and effluent concentrations remaining at about 0.7 μg/L, 3 μg/L and 10 ng/L respectively. The behavior of PFOS and 4-nonylphenol was singular, as concentrations were higher at the WWTP outlet than at its inlet. This was probably related to the degradation of some of their precursors (such as alkylphenol ethoxylates and polyfluorinated compounds resulting in 4-NP and PFOS, respectively) during biological treatment. 4-NP, ofloxacin, triclosan and perfluorinated compounds were found adsorbed on WAS (from 5 ng/kg for PFOA to 1.0mg/kg for triclosan). The statistical methods (principal component analysis and multiple linear regressions) were applied to examine relationships among the concentrations of micropollutants and macropollutants (COD, ammonium, turbidity) entering and leaving the WWTP. A strong relationship with ammonium indicated that some micropollutants enter wastewater via human urine. A statistical analysis of WWTP operation gave a model for estimating micropollutant output from the WWTP based on a measurement of macropollution parameters.

Photodegradation-based detection of fluorescent whitening agents in a mountain river

Fluorescent whitening agents (FWAs) are highly soluble and poorly biodegradable ingredients used in laundry detergents and in industries (paper, textile, plastic manufacturing). They are likely to pass through biological wastewater treatment systems. The presence of FWAs in a mountain river was detected by monitoring the decay of synchronous fluorescence intensity at λ(ex)=360 nm after exposing samples to ultraviolet (UV) light (365 nm), for mimicking sunlight, for 15 min. The method was first validated on four commercial FWAs (DAS-1, FB28, DMA-X and CBS-X) in different water matrices (deionized water and pristine river water in the presence of humic acid and dyes). A 40% decay was observed after 15 min for the least photosensitive FWA (CBS-X). A field application was then performed on samples collected along a mountain river in which impacts of FWAs from domestic sources (laundry greywater) and industrial sources (paper and textile mills) were suspected. Variations of fluorescence decay at λ(ex)=360 nm could be explained by these potential sources of pollution. It is suggested that the fluorescence decay at λ(ex)=280 nm also be considered as an indicator, as some FWAs can exhibit fluorescence at that excitation wavelength.

Assessment of field fluorometers

Two field fluorometers, devoted either to natural organic matter (NOM) or to tryptophan-like fluorescing substances, were tested for the characterization of a large set of water samples (n = 263) impacted to various degrees by untreated or poorly treated urban sewage. Both fluorometers yielded consistent results when testing discrete samples. A nonlinear correlation (coefficient of determination = 0.98) was found between the tryptophan concentration given by the tryptophan field fluorometer and the fluorescence intensity given by a bench-top fluorometer (excitation = 285 nm, emission = 335 nm), corresponding to tryptophan-like fluorescing substances. A linear correlation with a mediocre coefficient of determination (0.63) was found between the NOM concentration given by the NOM field fluorometer and the fluorescence intensity given by the bench-top fluorometer (excitation = 355 nm, emission = 405 nm). This could be related to the diversity of NOM present, as illustrated by the different shapes of synchronous fluorescence spectra collected for the same samples.

Impact of certain household micropollutants on bacterial behavior. Toxicity tests/study of extracellular polymeric substances in sludge

The impact of eight household micropollutants (erythromycin, ofloxacin, ibuprofen, 4-nonylphenol, triclosan, sucralose, PFOA and PFOS (PFAAs)) on the laboratory bacterial strain Escherichia coli MG1655 and on activated sludge from an urban wastewater treatment plant was studied. Growth-based toxicity tests on E. coli were performed for each micropollutants. The effect of micropollutants on activated sludge (at concentrations usually measured in wastewater up to concentrations disturbing the bacterial growth of E. coli) was examined in batch reactors and by comparison to a control reactor (without micropollutants). The bound extracellular polymeric substances (EPS) secreted by the sludge were measured by size exclusion chromatography and their overexpression was considered as an indicator of bacteria sensitivity to environmental changes. The chemical oxygen demand (COD) and the ammonium concentration were monitored to evaluate the biomass ability to remove the macropollution. Some micropollutants induced an increase of bound EPS in activated sludge flocs at concentrations depending on the micropollutant: erythromycin from 100 μg/L, ofloxacin from 10 μg/L, triclosan from 0.5 μg/L, 4-nonylphenol from 5000 μg/L and PFAAs from 0.1 μg/L. This suggests that the biomass had to cope with new conditions. Moreover, at high concentrations of erythromycin (10 mg/L) and ibuprofen (5 mg/L) bacterial populations were no longer able to carry out the removal of macropollution. Ibuprofen induced a decrease of bound EPS at all the studied concentrations, probably reflecting a decrease of general bacterial activity. The biomass was not sensitive to sucralose in terms of EPS production, however at very high concentration (1 g/L) it inhibited the COD decrease. Micropollution removal was also assessed. Ibuprofen, erythromycin, ofloxacin, 4-nonylphenol and triclosan were removed from wastewater, mainly by biodegradation. Sucralose and PFOA were not removed from wastewater at all, and PFOS was slightly eliminated by adsorption on sludge.

Dynamic assessment of the floc morphology, bacterial diversity, and integron content of an activated sludge reactor processing hospital effluent

The treatment of hospital effluents (HE) is a major concern, as they are suspected of disseminating drugs and antibiotic resistance determinants in the environment. In order to assess HE influence on wastewater treatment plant biomass, lab-scale conventional activated sludge systems (CAS) were continuously fed with real HE or urban effluent as a control. To gain insights into the main hurdles linked to HE treatment, we conducted a multiparameter study using classical physicochemical characterization, phase contrast and confocal laser scaning microscopy, and molecular biology (i.e., pyrosequencing) tools. HE caused erosion of floc structure and the production of extracellular polymeric substances attributed to the development of floc-forming bacteria. Adaptation of the sludge bacterial community to the HE characteristics, thus maintaining the purification performance of the biomass, was observed. Finally, the comparative metagenomic analysis of the CAS showed that HE treatment resulted in an increase of class 1 resistance integrons (RIs) and the introduction of Pseudomonas spp. into the bacterial community. HE treatment did not reduce the CAS process performance; nevertheless it increases the risk of dissemination into the environment of bacterial species and genetic determinants (RIs) involved in antibiotic resistance acquisition.

Comparison of photocatalytic degradation of dyes in relation to their structure

The photocatalytic degradation of a series of six acid dyes (Direct Red 80, Direct Red 81, Direct Red 23, Direct Violet 51, Direct Yellow 27, and Direct Yellow 50) has been tested compared in terms of color removal, mineralization, and toxicity (Lactuca sativa L. test) after photocatalysis on immobilized titanium dioxide. The dyes were examined at their natural pH and after hydrolysis at pH 12. Results show that hydrolysis decreases strongly the efficiency of color removal, that full mineralization takes much longer reaction time than color removal, and that toxicity is only very partially reduced. Some structural parameters, related to the structure and the topology of the dye molecules, could be correlated with the apparent color removal rates at natural pH.

Monitoring of slaughterhouse wastewater biodegradation in a SBR using fluorescence and UV-Visible absorbance

The aim of this study was to demonstrate that the effectiveness of slaughterhouse wastewater treatment by activated sludge could be enhanced through the use of optical techniques, such as UV-Visible absorbance and fluorescence spectroscopy, to estimate the hydraulic retention time necessary to remove the biodegradable chemical oxygen demand (COD). Two experiments were conducted. First, a batch aerobic degradation was performed on four wastewater samples collected from four different cattle processing sites in order to study the changes in the spectroscopic properties of wastewater during biodegradation. Second, a sequencing batch reactor was used in order to confirm that the wastewater fluorescence could be successfully used to monitor wastewater biodegradation in a pilot-scale experiment. Residual blood was the main source of organic matter in the wastewater samples. The absorbance at 416 nm, related to porphyrins, was correlated to the COD during wastewater biodegradation. The tryptophan-like/fulvic-like fluorescence intensity ratio was related to the extent of biodegradation. The COD removal efficiency ranged from 74% to 94% with an hydraulic retention time (HRT) of 23 h. A ratio of tryptophan-like/fulvic-like fluorescence intensities higher than 1.2 indicated incomplete biodegradation of the wastewater and the need to increase the HRT.

Spectrophotometric characterization of human impacted surface waters in the Moselle watershed

In order to characterize the pollution discharged into the Moselle River and some of its tributaries, spectroscopic techniques, namely UV-vis spectroscopy and synchronous fluorescence spectroscopy, have been combined. UV-visible spectra were analysed using the maximum of the second derivative at 225 nm (related to nitrates), the SUVA254 and E2/E3 indices (related to the nature of organic matter). Synchronous fluorescence spectra (delta lambda = 50 nm) presented different shapes depending upon the type of pollution. The pollution results from anthropogenic activities: untreated domestic sewage due to misconnections in a periurban river, effluent from urban WWTPS, agricultural runoff (nitrates) in several streams, discharge from a paper mill (humic-like substances due to wood processing) and from steel mills (PAHs).

Cadmium biosorption by ozonized activated sludge: the role of bacterial flocs surface properties and mixed liquor composition

Cadmium uptake by activated sludge was studied following modifications of sludge composition and surface properties induced by ozone treatment. Ozone leads to the solubilization of sludge compounds as well as their mineralization, especially humic like substances. Small particles were formed following floc disintegration, leading to a decrease of average floc size. The study of surface properties underlined the mineralization as the number of surface binding sites decreased with the increase of ozone dose. Depending on ozone dose, cadmium uptake by activated sludge flocs was either increased or decreased. Different mechanisms were involved: below 10 mg O(3)/g TS, the increase of floc specific surface area following floc size decrease as well as the release of phosphate ions yielded an increase by 75% of cadmium uptake, due to the better availability of biosorption sites and the increase of precipitation. Inversely, at higher ozone doses, the number of biosorption sites decreased due to oxidation by ozone. Moreover, dissolved organic matter concentration increased and provided ligands for metal complexation. Cadmium uptake was therefore limited for ozone doses ranging from 10 to 16.8 mg O(3)/g TS.

Adverse effects of erythromycin on the structure and chemistry of activated sludge

This study examines the effects of erythromycin on activated sludge from two French urban wastewater treatment plants (WWTPs). Wastewater spiked with 10 mg/L erythromycin inhibited the specific evolution rate of chemical oxygen demand (COD) by 79% (standard deviation 34%) and the specific N-NH4+ evolution rate by 41% (standard deviation 25%). A temporary increase in COD and tryptophan-like fluorescence, as well as a decrease in suspended solids, were observed in reactors with wastewater containing erythromycin. The destruction of activated sludge flocs was monitored by automated image analysis. The effect of erythromycin on nitrification was variable depending on the sludge origin. Erythromycin inhibited the specific nitrification rate in sludge from one WWTP, but increased the nitrification rate at the other facility.

Photocatalytic decolorisation and mineralisation of orange dyes on immobilised titanium dioxide nanoparticles

In this paper the photocatalytic decolorisation and mineralisation of three orange dyes (AO10, AO12 and AO8) in neutral, alkaline and hydrolysed solutions under UV light irradiation in the presence of TiO(2) nanoparticles has been compared. The investigated photocatalyst was Millennium PC-500 TiO(2) (crystallites mean size 5-10 nm) immobilised on non-woven paper. All the experiments were performed in a circulation photochemical reactor equipped with a 15 W UV lamp emitting around 365 nm. Results indicated that complete decolorisation of 250 mL pure dye solutions with initial dye concentration of 30 mg/L could be achieved in 140 min. Photocatalytic mineralisation of the neutral, alkaline and hydrolysed dye solutions was monitored by total organic carbon (TOC) decrease and ammonium ion formation. Results indicated that the photocatalytic decolorisation and mineralisation of the dyes was less efficient with the hydrolysed and alkaline dye solutions in comparison with the neutral pure dye solutions. The amount of NH(4)(+), as N-containing mineralisation product, during UV/TiO(2) process was analysed. The electrical energy consumption for photocatalytic decolorisation of the dyes was calculated and related to the treatment costs.

Activated sludge behaviour in a batch reactor in the presence of antibiotics: study of extracellular polymeric substances

The influence of Erythromycin, Roxithromycin, Amoxicillin, Tetracycline and Sulfamethoxazole on municipal sludge in batch reactors was investigated. The study was focused on extracellular polymeric substances (EPS) as indicator of bacteria sensitivity to toxic agents. The EPS were analysed by UV-Vis and FT-IR spectroscopies and by size exclusion chromatography. It was found that Erythromycin and Roxithromycin induced a significant increase of bound EPS in flocs. This was attributed to a protection mechanism of the bacteria. Erythromycin was the only antibiotic which inhibited COD and nitrogen removal.

Tylosin abatement in water by photocatalytic process

The photocatalytic degradation of a macrolide (tylosin) has been studied using immobilized titanium dioxide as photocatalyst in a laboratory reactor under UV illumination (365 nm). The degradation of the antibiotic and of the reaction intermediary product was monitored by UV spectrophotometry and HPLC. Three photocatalysts (P25 from Degussa and PC105 and PC500 from Millennium) immobilized on glass plates were compared. A slightly better degradation was obtained with P25. Then the tylosin degradation kinetics were investigated with the P25 photocatalyst. The kinetic model of Langmuir-Hinshelwood is satisfactorily obeyed at initial time and in the course of the reaction. Adsorption and apparent rate constants were determined. These results suggest that, although an intermediary by-product was detected during the reaction, complete degradation of tylosin can be achieved, which confirms the feasibility of such a photocatalytic treatment for tylosin elimination from wastewater.

Acute sensitivity of activated sludge bacteria to erythromycin

The presence of antibiotics in water resources has been disturbing news for the stakeholders who are responsible for public health and the drinking water supply. In many cases, biological wastewater treatment plants are the final opportunity in the water cycle to trap these substances. The sensitivity of activated sludge bacteria to erythromycin, a macrolide widely used in human medicine was investigated in batch toxicity tests using a concentration range of 1-300 mg L(-1). Erythromycin, a protein synthesis inhibitor, has been found to significantly inhibit ammonification, nitritation and nitratation at concentrations higher than 20 mg L(-1). The degree of inhibition increased with greater concentrations of the antibiotic. Exposure to erythromycin also clearly affected heterotrophs, particularly filamentous bacteria, causing floc disintegration and breakage of filaments. Cell lysis was observed with the concomitant release of organic nitrogen (intracellular proteins) and soluble COD. Although erythromycin exhibits properties of a surfactant, this characteristic alone cannot explain the damage to heterotrophs: the effects from erythromycin were greater than those of Tween 80, a commonly used surfactant. Floc disruption can lead to the release of isolated bacteria, and possibly antibiotic resistance genes, into the environment.

Photocatalytic degradation of three azo dyes using immobilized TiO2 nanoparticles on glass plates activated by UV light irradiation: influence of dye molecular structure

In order to discuss the effect of chemical structure on photocatalysis efficiency, the photocatalytic degradation of three commercial textile dyes (C.I. Acid Orange 10 (AO10), C.I. Acid Orange 12 (AO12) and C.I. Acid Orange 8 (AO8)) with different structure and different substitute groups has been investigated using supported TiO(2) photocatalyst under UV light irradiation. All the experiments were performed in a circulation photochemical reactor equipped with a 15-W UV lamp emitted around 365nm. The investigated photocatalyst was industrial Millennium PC-500 (crystallites mean size 5-10nm) immobilized on glass plates by a heat attachment method. SEM images of the immobilized TiO(2) nanoparticles showed the good coating on the plates, after repeating the deposition procedure three times. Our results indicated that the photocatalytic decolorization kinetics of the dyes were in the order of AO10>AO12>AO8. Photocatalytic mineralization of the dyes was monitored by total organic carbon (TOC) decrease, changes in UV-vis spectra and ammonium ion formation. The dye solutions could be completely decolorized and effectively mineralized, with an average overall TOC removal larger than 94% for a photocatalytic reaction time of 6h. The nitrogen-to-nitrogen double bond of the azo dyes was transformed predominantly into NH(4)(+) ion. The kinetic of photocatalytic decolorization of the dyes was found to follow a first-order rate law. The photocatalysis efficiency was evaluated by figure-of-merit electrical energy per order (E(EO)).

Flocs surface functionality assessment of sonicated activated sludge in relation with physico-chemical properties

Flocs surface functional groups evolutions due to an ultrasonic treatment were investigated in respect with the mechanisms involved during sonication. Activated sludge surface functional groups changes were studied after treatment of a sample at different ultrasonic specific energies. Sludge functionality was qualitatively assessed by recording the infrared (FT-IR) spectra of centrifugation pellets. Potentiometric titration coupled with proton surface complexation modeling was used to assess the nature and quantity of ionizable functional groups present at the floc surface and in the aqueous phase. These evolutions were linked to changes of both mixed liquor biochemical composition (TSS, VSS, COD, proteins, humic like substances, polysaccharides) and physical properties (floc size and settleability). Observations carried out showed that activated sludge flocs were essentially mechanically disintegrated by ultrasonic waves: the nature of chemical bonds observed by FT-IR did not shift after ultrasonic treatment. Moreover, the total number of ionizable functional groups measured by potentiometric titrations remained constant during sonication. However, due to the solubilization of organic components induced by cavitation process, the corresponding ionizable functional groups (carboxyl, hydroxyl, amine) were transferred from particulate to soluble fraction. Moreover, due to the variable amount of proteins, humic like substances and polysaccharides solubilised, the relative contributions of carboxyl, hydroxyl and amine groups varied at floc surface.