Efficacy of activated carbon filtration and ozonation to remove persistent and mobile substances - A case study in two wastewater treatment plants.

Persistent and mobile (PM) substances are able to spread quickly in the water cycle and were thus identified as potentially problematic for the environment and water quality. If also toxic (PMT) or very persistent and very mobile (vPvM) their regulation under REACH as substances of very high concern is foreseen. Yet, knowledge on the effectiveness of advanced wastewater treatment in removing PM-substances from WWTP effluents is limited to few rather well-known chemicals. The occurrence and behavior of 111 suspected and known PM-substances was investigated in two wastewater treatment plants employing either powdered activated carbon (PAC, full-scale) or ozonation with subsequent sand/anthracite filtration (pilot-scale) and an additional granular activated carbon (GAC) filtration was investigated. 72 of the 111 PM-substances analyzed were detected at least once in the secondary effluent of either wastewater treatment plant, resulting in total concentrations of 104 µg/L and 40 µg/L, respectively. While PAC removed 32 % of PM-substances well, the total PM burden in the effluent was only reduced from 103 µg/L to 87 µg/L. Ozonation and the subsequent sand/anthracite filtration was able to reduce the PM burden in wastewater from 40 µg/L to 19 µg/L, showing a higher removal efficacy than PAC in this study. The additional GAC filtration further reduced the total PM-concentration to 13 µg/L. Among the investigated PM-chemicals detected were constituents of ionic liquids: The anion hexafluorophosphate was one of few chemicals that was detected in effluent concentrations >1 µg/L and could not be removed by the processes studied, showing that for some chemicals preventive actions may be required.

Pilot-scale removal of persistent and mobile organic substances in granular activated carbon filters and experimental predictability at lab-scale.

Present knowledge about the fate of persistent and mobile (PM) substances in drinking water treatment is limited. Hence, this study assesses the potential of fixed-bed granular activated carbon (GAC) filters to fill the treatment gap for PM substances and the elimination predictability from lab-scale experiments. Two parallel pilot filters (GAC bed height 2 m, diameter 15 cm) with different GAC were operated for 1.5 years (ca. 47,000 BV throughput) alongside rapid small-scale column tests (RSSCT) designed based on the proportional diffusivity (PD) and the constant diffusivity (CD) approaches. Background dissolved organic matter (DOM) and a set of 17 target substances were investigated, among them 2-acrylamido-2-methylpropane sulfonate (AAMPS), adamantan-1-amine (ATA), melamine (MEL) and trifluoromethanesulfonic acid (TFMSA). Nine substances were predominantly present in the drinking water used as pilot filter influent (frequencies of detection above 80 %, median concentrations 0.003-1.868 µg/L) and their breakthrough behaviors could be observed: TFMSA was not retained at all, four substances including AAMPS and ATA reached complete breakthrough below 20,000 BV, three compounds were partially retained until the end of operation and oxypurinol was retained completely. The comparable PM candidate and DOM removal performances of both GAC aligns with their very similar surface characteristics and elemental compositions. The agreement of results between RSSCT with the pilot-scale filters were substance specific and no superior RSSCT design could be identified. However, CD-RSSCT provide a conservative removal prediction for most studied compounds. MEL adsorption was significantly underestimated by both RSSCT designs. Using the criterion of a carbon usage rate (with respect to 50 % breakthrough) below 25 mgGAC/Lwater for an economic retention by fixed-bed GAC filters, five (out of nine) substances met the requirement.

Is adsorption onto activated carbon a feasible drinking water treatment option for persistent and mobile substances?

Persistent and mobile (PM) substances among the organic micropollutants have gained increasing interest since their inherent properties enable them to enrich in water cycles. This study set out to investigate the potential of adsorption onto activated carbon as a drinking water treatment option for 19 PM candidates in batch experiments in a drinking water matrix using a microporous and a mesoporous activated carbon. Overall, adsorption of PM candidates proved to be very variable and the extent of removal could not be directly related to molecular properties. At an activated carbon dose of 10 mg/L and 48 h contact time, five (out of 19) substances were readily removed (≥ 80%), among them N-(3-(dimethylamino)-propyl)methacrylamide, which was investigated for the first time. For five other substances, no or negligible removal (< 20%) was observed, including 2-methyl-2-propene-1-sulfonic acid and 4­hydroxy-1-(2-hydroxyethyl)-2,2,6,6,-tetramethylpiperidine. For the former, current state of the art adsorption processes may pose a sufficient barrier. Additionally, substance specific surrogate correlations between removals and UVA254 abatements were established to provide a cheap and fast estimate for PM candidate elimination. Adsorption onto activated carbon could contribute significantly to PM substance elimination as part of multi barrier approaches, but assessments for individual substances still require clarification, as demonstrated for the investigated PM candidates.

Filling the knowledge gap: A suspect screening study for 1310 potentially persistent and mobile chemicals with SFC- and HILIC-HRMS in two German river systems.

Persistent and mobile chemicals (PM chemicals) were searched for in surface waters by hydrophilic interaction liquid chromatography (HILIC) and supercritical fluid chromatography (SFC), both coupled to high resolution mass spectrometry (HRMS). A suspect screening was performed using a newly compiled list of 1310 potential PM chemicals to the data of 11 surface water samples from two river systems. In total, 64 compounds were identified by this approach. The overlap between HILIC- and SFC-HRMS was limited (31 compounds), confirming the complementarity of the two methods used. The identified PM candidates are characterized by a high polarity (median logD -0.4 at pH 7.5), a low molecular weight (median 187 g/mol), are mostly ionic (54 compounds) and contain a large number of heteroatoms (one per four carbons on average). Among the most frequently detected novel or yet scarcely investigated water contaminants were cyanoguanidine (11/11 samples), adamantan-1-amine (10/11), trifluoromethanesulfonate (9/11), 2-acrylamido-2-methylpropanesulfonate (10/11), and the inorganic anions hexafluorophosphate (11/11) and tetrafluoroborate (10/11). 31% of the identified suspects are mainly used in ionic liquids, a chemically diverse group of industrial chemicals with numerous applications that is so far rarely studied for their occurrence in the environment. Prioritization of the findings of PM candidates is hampered by the apparent lack of toxicity data. Hence, precautionary principles and minimization approaches should be applied for the risk assessment and risk management of these substances. The large share of novel water contaminants among these findings of the suspect screening indicates that the universe of PM chemicals present in the environment has so far only scarcely been explored. Dedicated analytical methods and screening lists appear essential to close the analytical gap for PM compounds.

Sources and Fate of the Antiandrogenic Fluorescent Dye 4-Methyl-7-Diethylaminocoumarin in Small River Systems.

Recently, the potent antiandrogen 4-methyl-7-diethylaminocoumarin (C47) and its potential transformation products 4-methyl-7-ethylaminocoumarin (C47T1) and 4-methyl-7-aminocoumarin (C47T2) were identified as novel environmental contaminants. We assessed for the first time the sources, distribution, and fate of these compounds in aquatic systems using the Holtemme River (Saxony-Anhalt, Germany), which is a hotspot for these contaminants. To this end, wastewater-treatment plant (WWTP) influent and effluent samples, surface water samples over 3 years, and the longitudinal profiles in water, sediment, and gammarids were analyzed. From the longitudinal profile of the river stretch, the WWTP of Silstedt was identified as the sole point source for these compounds in the River Holtemme, and exposure concentrations in the low micrograms per liter range could be recorded continuously over 3 years. Analysis of WWTP influent and effluent showed a transformation of approximately half of the C47 into C47T1 and C47T2 but no complete removal. A further attenuation of the three coumarins after discharge into the river could be largely attributed to dilution, while transformation was only approximately 20%, thus suggesting a significant persistence in aquatic systems. Experimentally derived partitioning coefficients between water and sediment organic carbon exceeded those predicted using the OPERA quantitative structure-activity relationship tools and polyparameter linear free-energy relationships by up to 93-fold, suggesting cation binding as a significant factor for their sorption behavior. Near-equilibrium conditions between water and sediment were not observed close to the emitting WWTP but farther downstream in the river. Experimental and predicted bioaccumulation factors for gammarids were closely matching, and the concentrations in field-sampled gammarids were close to steady state with exposure concentrations in the water phase of the river. Environ Toxicol Chem 2021;40:3078-3091. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Ozonation products from trace organic chemicals in municipal wastewater and from metformin: peering through the keyhole with supercritical fluid chromatography-mass spectrometry.

Ozonation is an important process to further reduce the trace organic chemicals (TrOCs) in treated municipal wastewater before discharge into surface waters, and is expected to form products that are more oxidized and more polar than their parent compounds. Many of these ozonation products (OPs) are biodegradable and thus removed by post-treatment (e.g., aldehydes). Most studies on OPs of TrOCs in wastewater rely on reversed-phase liquid chromatography- mass spectrometry (RPLC-MS), which is not suited for highly polar analytes. In this study, supercritical fluid chromatography combined with high resolution MS (SFC-HRMS) was applied in comparison to the generic RPLC-HRMS to search for OPs in ozonated wastewater treatment plant effluent at pilot-scale. While comparable results were obtained from these two techniques during suspect screenings for known OPs, a total of 23 OPs were only observed by SFC-HRMS via non-targeted screening. Several SFC-only OPs were proposed as the derivatives of methoxymethylmelamines, phenolic sulfates/sulfonates, and metformin; the latter was confirmed by laboratory-scale ozonation experiments. A complete ozonation pathway of metformin, a widespread and extremely hydrophilic TrOC in aquatic environment, was elaborated based on SFC-HRMS analysis. Five of the 10 metformin OPs are reported for the first time in this study. Three different dual-media filters were compared as post-treatments, and a combination of sand/anthracite and fresh post-granular activated carbon proved most effective in OPs removal due to the additional adsorption capacity. However, six SFC-only OPs, two of which originating from metformin, appeared to be persistent during all post-treatments, raising concerns on their occurrence in drinking water sources impacted by wastewater.

Disentangling multiple chemical and non-chemical stressors in a lotic ecosystem using a longitudinal approach.

Meeting ecological and water quality standards in lotic ecosystems is often failed due to multiple stressors. However, disentangling stressor effects and identifying relevant stressor-effect-relationships in complex environmental settings remain major challenges. By combining state-of-the-art methods from ecotoxicology and aquatic ecosystem analysis, we aimed here to disentangle the effects of multiple chemical and non-chemical stressors along a longitudinal land use gradient in a third-order river in Germany. We distinguished and evaluated four dominant stressor categories along this gradient: (1) Hydromorphological alterations: Flow diversity and substrate diversity correlated with the EU-Water Framework Directive based indicators for the quality element macroinvertebrates, which deteriorated at the transition from near-natural reference sites to urban sites. (2) Elevated nutrient levels and eutrophication: Low to moderate nutrient concentrations together with complete canopy cover at the reference sites correlated with low densities of benthic algae (biofilms). We found no more systematic relation of algal density with nutrient concentrations at the downstream sites, suggesting that limiting concentrations are exceeded already at moderate nutrient concentrations and reduced shading by riparian vegetation. (3) Elevated organic matter levels: Wastewater treatment plants (WWTP) and stormwater drainage systems were the primary sources of bioavailable dissolved organic carbon. Consequently, planktonic bacterial production and especially extracellular enzyme activity increased downstream of those effluents showing local peaks. (4) Micropollutants and toxicity-related stress: WWTPs were the predominant source of toxic stress, resulting in a rapid increase of the toxicity for invertebrates and algae with only one order of magnitude below the acute toxic levels. This toxicity correlates negatively with the contribution of invertebrate species being sensitive towards pesticides (SPEARpesticides index), probably contributing to the loss of biodiversity recorded in response to WWTP effluents. Our longitudinal approach highlights the potential of coordinated community efforts in supplementing established monitoring methods to tackle the complex phenomenon of multiple stress.

Determination of transformation products of per- and polyfluoroalkyl substances at trace levels in agricultural plants.

Per- and polyfluoroalkyl substances (PFASs) are ubiquitous in the environment. However, only a limited number of predominantly persistent perfluoroalkyl acids (PFAAs) have been analyzed in edible plants so far. We present a generic trace analytical method that allows for quantification of 16 intermediate fluorotelomer alcohol (FTOH)- or perfluoroalkane sulfonamidoethanol (FASE)-based transformation products as well as 18 PFAAs in plants. Additionally, 36 suspected intermediate PFAS transformation products were qualitatively analyzed. The ultrasound-assisted solid-liquid extraction of wheat and maize grain, maize leaves, Jerusalem artichoke and ryegrass (1-5 g plant sample intake) was followed by a clean-up with dispersive solid-phase extraction using graphitized carbon adsorbent (5-10 mg per sample) and chemical analysis by reversed phase liquid chromatography-tandem mass spectrometry. The method was based on matrix matched and extracted calibration and displayed good precision with relative standard deviations in triplicate analyses typically below 15% for all quantified analytes and matrices. An average deviation of 12% between quantified concentrations obtained by matrix matched and extracted calibration and a method based on isotopically labelled internal standards underlines the good trueness of the method. The method quantification limits for the majority of analytes in all plant samples were in the low ng/kg concentration range on a dry weight basis. Plant matrices were analyzed from crops grown on agricultural fields that have been contaminated with PFASs. FTOH- and/or FASE-based intermediate transformation products were detected in all samples with N-ethyl perfluorooctane sulfonamidoacetic acid (EtFOSAA) and perfluorooctane sulfonamide (FOSA) as the prevailing compounds in concentrations up to several hundred ng/kg in maize leaves. The 9:3 Acid (a transformation product of 10:2 FTOH) was tentatively identified. In accordance with these findings, the final degradation products perfluorooctane sulfonic acid (PFOS) and perfluorodecanoic acid (PFDA) were frequently detected. For perfluoroalkyl carboxylic acids (PFCAs), according to earlier findings, short chain homologues generally displayed the highest levels (up to 98 µg/kg for perfluorobutanoic acid (PFBA) in maize leaves). However, maize grain was an exception showing the highest concentrations for long chain PFCAs, whereas PFBA was not detected. The uptake of high levels of PFASs into plants is of concern since these may be used as animal feed or represent a direct exposure medium for humans.

A rapid method for quantification of persistent and mobile organic substances in water using supercritical fluid chromatography coupled to high-resolution mass spectrometry.

Persistent and mobile organic substances (PM substances) are a threat to the quality of our water resources. While screening studies revealed widespread occurrence of many PM substances, rapid trace analytical methods for their quantification in large sample sets are missing. We developed a quick and generic analytical method for highly mobile analytes in surface water, groundwater, and drinking water samples based on enrichment through azeotrope evaporation (4 mL water and 21 mL acetonitrile), supercritical fluid chromatography (SFC) coupled to high-resolution mass spectrometry (HRMS), and quantification using a compound-specific correction factor for apparent recovery. The method was validated using 17 PM substances. Sample preparation recoveries were between 60 and 110% for the vast majority of PM substances. Strong matrix effects (most commonly suppressive) were observed, necessitating a correction for apparent recoveries in quantification. Apparent recoveries were neither concentration dependent nor dependent on the water matrix (surface or drinking water). Method detection and quantification limits were in the single- to double-digit ng L-1 ranges, precision expressed as relative standard deviation of quadruplicate quantifications was on average < 10%, and trueness experiments showed quantitative results within ± 30% of the theoretical value in 77% of quantifications. Application of the method to surface water, groundwater, raw water, and finished drinking water revealed the presence of acesulfame and trifluoromethanesulfonic acid up to 70 and 19 µg L-1, respectively. Melamine, diphenylguanidine, p-dimethylbenzenesulfonic acid, and 4-hydroxy-1-(2-hydroxyethyl)-2,2,6,6-tetramethylpiperidine were found in high ng L-1 concentrations. Graphical abstract.

Identification of Unknown Antiandrogenic Compounds in Surface Waters by Effect-Directed Analysis (EDA) Using a Parallel Fractionation Approach.

Among all the nuclear-receptor mediated endocrine disruptive effects, antiandrogenicity is frequently observed in aquatic environments and may pose a risk to aquatic organisms. Linking these effects to responsible chemicals is challenging and a great share of antiandrogenic activity detected in the environment has not been explained yet. To identify drivers of this effect at a hot spot of antiandrogenicity in the German river Holtemme, we applied effect-directed analysis (EDA) including a parallel fractionation approach, a downscaled luciferase reporter gene cell-based anti-AR-CALUX assay and LC-HRMS/MS nontarget screening. We identified and confirmed the highly potent antiandrogen 4-methyl-7-diethylaminocoumarin (C47) and two derivatives in the active fractions. The relative potency of C47 to the reference compound flutamide was over 5.2, whereas the derivatives were less potent. C47 was detected at a concentration of 13.7 µg/L, equal to 71.4 µg flutamide equivalents per liter (FEq/L) in the nonconcentrated water extract that was posing an antiandrogenic activity equal to 45.5 (±13.7 SD) FEq/L. Thus, C47 was quantitatively confirmed as the major cause of the measured effect in vitro. Finally, the antiandrogenic activity of C47 and one derivate was confirmed in vivo in spiggin-gfp Medaka. An endocrine disrupting effect of C47 was observed already at the concentration equal to the concentration in the nonconcentrated water extract, underlining the high risk posed by this compound to the aquatic ecosystem. This is of some concern since C47 is used in a number of consumer products indicating environmental as well as human exposure.

Downscaling procedures reduce chemical use in androgen receptor reporter gene assay.

Bioactivity screening studies often face sample amount limitation with respect to the need for reliable, reproducible and quantitative results. Therefore approaches that minimize sample use are needed. Low-volume exposure and chemical dilution procedures were applied in an androgen receptor reporter gene human cell line assay to evaluate environmental contaminants and androgen receptor modulators, which were the agonist 5α-dihydrotestosterone (DHT); and the antagonists flutamide, bisphenol A, 1-hydroxypyrene and triclosan. Cells were exposed in around 1/3 of the medium volume recommended by the protocol (70µL/well). Further, chemical losses during pipetting steps were minimized by applying a low-volume method for compound dilution in medium (250µL for triplicate wells) inside microvolume glass inserts. Simultaneously, compounds were evaluated following conventional procedures (200µL/well, dilution in 24-well plates) for comparison of results. Low-volume exposure tests produced DHT EC50 (3.4-3.7×10(-10)M) and flutamide IC50 (2.2-3.3×10(-7)M) values very similar to those from regular assays (3.1-4.2×10(-10) and 2.1-3.3×10(-7)M respectively) and previous studies. Also, results were within assay acceptance criteria, supporting the relevance of the downscaling setup for agonistic and antagonistic tests. The low-volume exposure was also successful in determining IC50 values for 1-hydroxypyrene (2.1-2.8×10(-6)M), bisphenol A (2.6-3.3×10(-6)M), and triclosan (1.2-1.9×10(-6)M) in agreement with values obtained through high-volume exposure (2.3-2.8, 2.5-3.4 and 1.0-1.3×10(-6)M respectively). Finally, experiments following both low-volume dosing and exposure produced flutamide and triclosan IC50 values similar to those from regular tests. The low-volume experimental procedures provide a simple and effective solution for studies that need to minimize bioassay sample use while maintaining method reliability. The downscaling methods can be applied for the evaluation of samples, fractions or chemicals which require minimal losses during the steps of pipetting, transference to medium and exposure in bioassays.

Effect-directed analysis supporting monitoring of aquatic environments--An in-depth overview.

Aquatic environments are often contaminated with complex mixtures of chemicals that may pose a risk to ecosystems and human health. This contamination cannot be addressed with target analysis alone but tools are required to reduce this complexity and identify those chemicals that might cause adverse effects. Effect-directed analysis (EDA) is designed to meet this challenge and faces increasing interest in water and sediment quality monitoring. Thus, the present paper summarizes current experience with the EDA approach and the tools required, and provides practical advice on their application. The paper highlights the need for proper problem formulation and gives general advice for study design. As the EDA approach is directed by toxicity, basic principles for the selection of bioassays are given as well as a comprehensive compilation of appropriate assays, including their strengths and weaknesses. A specific focus is given to strategies for sampling, extraction and bioassay dosing since they strongly impact prioritization of toxicants in EDA. Reduction of sample complexity mainly relies on fractionation procedures, which are discussed in this paper, including quality assurance and quality control. Automated combinations of fractionation, biotesting and chemical analysis using so-called hyphenated tools can enhance the throughput and might reduce the risk of artifacts in laboratory work. The key to determining the chemical structures causing effects is analytical toxicant identification. The latest approaches, tools, software and databases for target-, suspect and non-target screening as well as unknown identification are discussed together with analytical and toxicological confirmation approaches. A better understanding of optimal use and combination of EDA tools will help to design efficient and successful toxicant identification studies in the context of quality monitoring in multiply stressed environments.

Separation of multiphosphorylated peptide isomers by hydrophilic interaction chromatography on an aminopropyl phase.

The separation of isomeric phosphorylated peptides is challenging and often impossible for multiphosphorylated isomers using chromatographic and capillary electrophoretic methods. In this study we investigated the separation of a set of single-, double-, and triple-phosphorylated peptides (corresponding to the human tau protein) by ion-pair reversed-phase chromatography (IP-RPC) and hydrophilic interaction chromatography (HILIC). In HILIC both hydroxyl and aminopropyl stationary phases were tested with aqueous acetonitrile in order to assess their separation efficiency. The hydroxyl phase separated the phosphopeptides very well from the unphosphorylated analogue, while on the aminopropyl phase even isomeric phosphopeptides attained baseline separation. Thus, up to seven phosphorylated versions of a given tau domain were separated. Furthermore, the low concentration of an acidic ammonium formate buffer allowed an online analysis with electrospray ionization tandem mass spectrometry (ESI-MS/MS) to be conducted, enabling peptide sequencing and identification of phosphorylation sites.