Micropollutants Research Articles

Biochar obtained from recovered cellulose and its mixture with conventional sources: Assessment of its potential for the removal of pollutants in water

Yearly thousands of tons of cellulose, in the form of toilet paper, end up in the wastewater treatment plants (WWTP) through the sewage. Cellulose was recovered with a 0.35 mm sieve and processed obtaining three different pellets: pure cellulose, straw mix (50 % cellulose-50 % straw) and wood mix (50 % cellulose-50 % wood). Those materials were carbonized at 750 °C for 210 min producing non-activated biochar. Then, a part of those biochars was biologically activated by fermentation adding minerals, nutrients and a mixture of bacteria. All biochar versions were characterized, assessing the surface, porosity and adsorption capacity for a dye (indigo carmine) and a selection of 5 micropollutants (MPs): benzotriazole, carbamazepine, clarithromycin, DEET, and diclofenac. However, results showed that conventional analysis for adsorbents was not adequate for biologically activated materials since biofilm can obstruct the pores of the supporting material hindering the pollutants' adsorption. Therefore, the biological degradation of the pollutants by the microorganisms was also tested. Finally, biologically activated WOW-Biochar straw mix was the selected material to be further applied in constructed wetlands (CW) due to its higher average MPs removal capacity. Validation test at mesocosm scale demonstrates the suitability of the material as an admixture in CW, reaching a MPs removal rate higher than the 90 % regarding the WWTP inlet.

Machine Learning Models to Predict Early Breakthrough of Recalcitrant Organic Micropollutants in Granular Activated Carbon Adsorbers.

Granular activated carbon (GAC) adsorption is frequently used to remove recalcitrant organic micropollutants (MPs) from water. The overarching aim of this research was to develop machine learning (ML) models to predict GAC performance from adsorbent, adsorbate, and background water matrix properties. For model calibration, MP breakthrough curves were compiled and analyzed to determine the bed volumes of water that can be treated until MP breakthrough reaches ten percent of the influent MP concentration (BV10). Over 400 data points were split into training, validation, and testing sets. Seventeen variables describing MP, background water matrix, and GAC properties were explored in ML models to predict log10-transformed BV10 values. Using the ML models on the testing set, predicted BV10 values exhibited mean absolute errors of ∼0.12 log units and were highly correlated with experimentally determined values (R2 ≥ 0.88). The top three drivers influencing BV10 predictions were the air-hexadecane partition coefficient and hydrogen bond acidity (Abraham parameters L and A) of the MPs and the dissolved organic carbon concentration of the GAC influent water. The model can be used to rapidly estimate the GAC bed life, select effective GAC products for a given treatment scenario, and explore the suitability of GAC treatment for remediating emerging MPs.

Crucial role of nitrogen vacancies in carbon activated persulfate toward nonradical abatement of micropollutants from secondary effluent

Biomass-derived carbonaceous materials exhibit fascinating potentials in nonradical oxidation of micropollutants (MPs) by activating persulfate and their performances mainly rest on graphitic N. However, the simultaneously derived N vacancy received little attention. Herein, a graphene-like material rich in N vacancy was synthesized from coffee residues. It showed excellent removal efficiency (95 %) and degradation kinetics (0.21 min−1) in abating tetracycline antibiotics from secondary effluent and significant biotoxicity was diminished. Solid nonradical oxidation consisting of electron transfer (89 %) and singlet oxygen (1O2) oxidation (11 %) was determined. By tracking 1O2 source and electron flow, ketone group appeared at N vacancy was found as the critical site to grab electrons from peroxydisulfate (PDS) with production of 1O2. Then the electrons were transferred to graphitic N driven by the microelectric field between them. This work notices the function of vacancies in biomass resources for high-efficient removal of MPs from real water matrix.

Enhanced Degradation of Micropollutants in a Peracetic Acid/Mn(II) System with EDDS: An Investigation of the Role of Mn Species.

Extensive research has been conducted on the utilization of a metal-based catalyst to activate peracetic acid (PAA) for the degradation of micropollutants (MPs) in water. Mn(II) is a commonly employed catalyst for homogeneous advanced oxidation processes (AOPs), but its catalytic performance with PAA is poor. This study showed that the environmentally friendly chelator ethylenediamine-N,N'-disuccinic acid (EDDS) could greatly facilitate the activation of Mn(II) in PAA for complete atrazine (ATZ) degradation. In this process, the EDDS enhanced the catalytic activity of manganese (Mn) and prevented disproportionation of transient Mn species, thus facilitating the decay of PAA and mineralization of ATZ. By employing electron spin resonance detection, quenching and probe tests, and 18O isotope-tracing experiments, the significance of high-valent Mn-oxo species (Mn(V)) in the Mn(II)-EDDS/PAA system was revealed. In particular, the involvement of the Mn(III) species was essential for the formation of Mn(V). Mn(III) species, along with singlet oxygen (1O2) and acetyl(per)oxyl radicals (CH3C(O)O•/CH3C(O)OO•), also contributed partially to ATZ degradation. Mass spectrometry and density functional theory methods were used to study the transformation pathway and mechanism of ATZ. The toxicity assessment of the oxidative products indicated that the toxicity of ATZ decreased after the degradation reaction. Moreover, the system exhibited excellent interference resistance toward various anions and humid acid (HA), and it could selectively degrade multiple MPs.

Uncertainty in Environmental Micropollutant Modeling.

Water pollution policies have been enacted across the globe to minimize the environmental risks posed by micropollutants (MPs). For regulative institutions to be able to ensure the realization of environmental objectives, they need information on the environmental fate of MPs. Furthermore, there is an urgent need to further improve environmental decision-making, which heavily relies on scientific data. Use of mathematical and computational modeling in environmental permit processes for water construction activities has increased. Uncertainty of input data considers several steps from sampling and analysis to physico-chemical characteristics of MP. Machine learning (ML) methods are an emerging technique in this field. ML techniques might become more crucial for MP modeling as the amount of data is constantly increasing and the emerging new ML approaches and applications are developed. It seems that both modeling strategies, traditional and ML, use quite similar methods to obtain uncertainties. Process based models cannot consider all known and relevant processes, making the comprehensive estimation of uncertainty challenging. Problems in a comprehensive uncertainty analysis within ML approach are even greater. For both approaches generic and common method seems to be more useful in a practice than those emerging from ab initio. The implementation of the modeling results, including uncertainty and the precautionary principle, should be researched more deeply to achieve a reliable estimation of the effect of an action on the chemical and ecological status of an environment without underestimating or overestimating the risk. The prevailing uncertainties need to be identified and acknowledged and if possible, reduced. This paper provides an overview of different aspects that concern the topic of uncertainty in MP modeling.

Loss of micropollutants on syringe filters during sample filtration: Machine learning approach for selecting appropriate filters

Prefiltration before chromatographic analysis is critical in the monitoring of environmental micropollutants (MPs). However, in an aqueous matrix, such monitoring often leads to out-of-specification results owing to the loss of MPs on syringe filters. Therefore, this study investigated the loss of seventy MPs on eight different syringe filters by employing Random Forest, a machine learning algorithm. The results indicate that the loss of MPs during filtration is filter specific, with glass microfiber and polytetrafluoroethylene filters being the most effective (<20%) compared with nylon (>90%) and others (regenerated-cellulose, polyethersulfone, polyvinylidene difluoride, cellulose acetate, and polypropylene). The Random Forest classifier showed outstanding performance (accuracy range 0.81–0.95) for determining whether the loss of MPs on filters exceeded 20%. Important factors in this classification were analyzed using the SHapley Additive exPlanation value and Kruskal–Wallis test. The results show that the physicochemical properties (LogKow/LogD, pKa, functional groups, and charges) of MPs are more important than the operational parameters (sample volume, filter pore size, diameter, and flow rate) in determining the loss of most MPs on syringe filters. However, other important factors such as the implications of the roles of pH for nylon and pre-rinsing for PTFE syringe filters should not be ignored. Overall, this study provides a systematic framework for understanding the behavior of various MP classes and their potential losses on syringe filters.

Ozone Strong Water Dosing as Optimized Ozonation Process for Micropollutants Reduction in Wastewater Treatment Plants

ABSTRACT Growing concern over potential ecotoxicological problems caused by micropollutants (MPs) in water has led to the application of adsorptive and oxidative advanced treatment technologies at European wastewater treatment plants (WWTPs). Direct dosage of gaseous ozone via diffusers or pump-injection systems is the most common large-scale process applied in water and wastewater treatment. Studies point out that MP removal may take place via the direct, very selective reaction with the ozone molecule as well as the indirect reaction with the very reactive but nonselective hydroxyl radicals. Several process parameters and set-ups may affect the MPs elimination and inhibit or even cause the formation of transformation products (TPs) such as bromate. This work compares an alternative ozone application procedure (the so-called ‘ozone strong water’ dosing – OSW) with standard systems regarding MP elimination, ozone consumption, reaction time, and required plant space. A full-scale OSW system was installed and operated at the WWTP Duisburg-Vierlinden. A significant reduction in the time required to achieve the maximum possible elimination was observed for all six MPs investigated, with a hydraulic reaction time of 8 min. According to a theoretical calculation, the reactor volume could be reduced by two-thirds of the installed volume.

Occurrence of micropollutants in rural domestic wastewater in Zhejiang Province, China and corresponding wastewater-based epidemiology analysis

By 2021, rural regions in China were occupied by over 500 million residents, generating an annual volume of 19.5 billion m3 of rural domestic wastewater (RDW). This study aimed to investigate the occurrence and removal of micropollutants (MPs) in RDW treatment facilities and to perform a corresponding wastewater-based epidemiology analysis (WBE). Our findings indicated the significantly high levels of influent MPs, particularly pharmaceuticals, such as ofloxacin and diclofenac being most prevalent (ranging from several to tens of μg/L) across different facilities. After various treatments, regular water indexes in the effluent, like NH3 -N and COD, have basically satisfied the local discharge standard. However, the concentration of certain dominant MPs in effluent remained notably high, ranging from hundreds of ng/L to several μg/L. The risk quotients of MPs like diclofenac, ciprofloxacin, ofloxacin, sulfamethoxazole, diuron, and isoproturon were all above 1 in the effluent, signifying significant hazards to aquatic organisms. The quantitative meta-analysis revealed higher average standardized removal efficiency for membrane bioreactor (MBR) treatment (-11 %) compared to anaerobic/anoxic/aerobic (A2O) treatment (11 %), indicating the higher efficiency of MBR treatment in outperforming the A2O as a secondary treatment. Additionally, employing biofilter as a tertiary treatment proved to be more effective as compared to flocculation-air flotation and artificial wetlands. Moreover, the results of WBE analysis showed that diclofenac and ofloxacin emerged as the most commonly used pharmaceuticals (of seven), with consumption levels recorded at 1222 and 517 mg/(d·103 capita), with daily defined doses per day per 103 capita of 12.2/1000 and 1.29/1000, respectively. This study addresses the existing knowledge gaps regarding the occurrence and removal of MPs in RDW and offers valuable insights into pharmaceutical consumption patterns in rural regions, thereby improving our understanding of public health.

Biochar from recovered cellulose as new admixture in constructed wetlands for micropollutant removal: A circular approach

This study aimed to evaluate the suitability of biochar produced by pyrolysis from recovered wastewater cellulose and activated biologically as an admixture in Constructed Wetlands (CWs) when applied as a post-treatment step to remove micropollutants (MPs) from municipal wastewater effluent. Two planted vertical flow mesocosm CWs with cellulose-based admixtures of different origins (plant residue and recovered toilet paper) were fed with a municipal wastewater effluent representative for rural catchments. The results showed an average MPs elimination of 89.1 % for the activated biochar produced from recovered cellulose when 15 relevant compounds are considered and a reduction of the risk from compounds cocktail below the maximum acceptable level having diclofenac, carbamazepine, PFOS, ciprofloxacin and clarithromycin as main risk drivers (Risk Quotient > 1). The implementation of a circular approach to reduce MPs was finally conducted for the Blies catchment (Saarland region in Germany) characterized by low population density and small, sensitive water bodies. This approach demonstrates the feasibility of combining cellulose recovery with a fine sieve in large wastewater treatment plants (WWTPs) and providing biochar produced from recovered cellulose as an admixture to small WWTP where CW is an affordable solution for MP mitigation.

Feasibility study of powdered activated carbon membrane bioreactor (PAC-MBR) for source-separated urine treatment: A comparison with MBR

Micropollutants (MPs) such as pharmaceuticals and personal care products are a group of emerging environmental contaminants, which are structurally complex and can cause adverse physiological effects on human health at low concentration. This study demonstrated that a hybrid process of powdered activated carbon and microfiltration membrane bioreactor (PAC-MBR) could be utilized for efficient removal of metronidazole, acetaminophen, naproxen, ibuprofen, carbamazepine, estriol (> 99 %) from source-separated urine via physical adsorption and biodegradation in a single step, without compromising the operating system stability. PAC addition to MBR improved 5 % of nitrification performance in terms of ammonia to nitrate conversion rate. Further, it improved organic removal efficiency from 88.6 ± 2.9 % to 96.0 ± 1.2 %, promoted rapid biomass growth, increased sludge floc size growth by 17 % and reduced membrane fouling propensities. This study showed the production of a micropollutant-free fertiliser from source-separated urine achieving a complete nutrient recovery in a single stage MBR system.

Ferrate(VI)/percarbonate for the oxidation of micropollutants: Interactive activation and release of low-concentration hydrogen peroxide for efficient electron utilization

A novel "ferrate/percarbonate (Fe(VI)/SPC) co-oxidation process" was used to treat ciprofloxacin (CIP) and various micropollutants (MPs), which owned better performance than mixture of Fe(VI), Na2CO3 and H2O2. The mechanism investigation found that the low-concentration H2O2 (1–2 µM) released by SPC can promote the high-valent iron intermediates (Fe(IV)/Fe(V)) of Fe(VI) to the MP oxidation, and Fe(VI) products can also activate SPC to produce hydroxyl radical (·OH). The interactive activation of Fe(VI) and SPC was realized, which retained the high selectivity of Fe(VI) to electron-rich pollutants, and also made up the oxidation of electron-deficient pollutants through •OH, improving the degradation effect of various MPs by 20–30%, and the rate constant was increased by 1 to 3 times. Moreover, non-purgeable organic carbon (NPOC) determination confirmed that •OH participation reduced the NPOC value of CIP from 5.43 mg/L to 4.37 mg/L. The transformation pathway of CIP showed that Fe(VI)/SPC resulted in more hydroxylation intermediates of CIP than Fe(VI) alone. Acute toxicity assays found that the photoinhibition rate of CIP treated with Fe(VI) alone was 14.5%, while the sample treated with Fe(VI)/SPC showed no significant photoinhibition effect, which proved that the new process had good detoxification properties for CIP.

A harmonized Danube basin-wide multi-compartment concentration database to support inventories of micropollutant emissions to surface waters

BackgroundThe European Water Framework Directive foresees the establishment of emission inventories for micropollutants (MP) to facilitate an evidence-based development of mitigation measures. Regionalized pathway analysis constitutes a moderately data-intensive approach to quantify the contribution of different pathways to the total pollution of surface waters. So far, only few European member states have created an inventory that includes diffuse pathways. The fundamental basis to enable it is an accessible, well-structured and harmonized database with data on the concentration of MPs in multiple compartments, such as soils, groundwater, atmospheric deposition and urban systems. Combined with the water and suspended substance balance in river basins, such data enables the estimation of emission loads via specific pathways. In the Danube River Basin, but in general in Europe, a public data management platform with such scope and criteria is still lacking.ResultsWe collected and harmonized MP measurements across multiple compartments and countries together with key metadata, harmonized and combined them into a new database. The resulting tool, available for download, facilitates the assessment of current data availability, in terms of quantity and quality. For example, while the majority of available data stems from groundwater and surface water, other highly relevant compartments are scarcely represented. By examining differences in MP concentration level across compartments, the database can lead to understand the relevance of specific emission pathways and thus to prioritize data-retrieval and calculation efforts in modelling applications. Selected examples show how to exploit the metadata associated to the measurements to extrapolate the results to regions not covered by specific monitoring programmes. For example, PFAS concentrations in treated wastewater show significant dependence on the design capacity of the treatment plant.ConclusionsThis study showcases how such database can support the setup of emission inventories, guide data providers and national authorities in prioritizing the allocation of resources for new surveys and in optimizing their national data collection and management systems. The process tested showed a great need for enhanced data literacy across countries and institutions to increase data availability and quality to secure the exploitation of the full information potential generated via monitoring programmes.

Efficiency of ozonation and sulfate radical - AOP for removal of pharmaceuticals, corrosion inhibitors, x-ray contrast media and perfluorinated compounds from reverse osmosis concentrates

This study investigated the elimination of pharmaceuticals, corrosion inhibitors, x-ray contrast media and perfluorinated compounds from reverse osmosis concentrates during ozonation and UV/persulfate processes. Second-order rate constants for the reactions of candesartan, irbesartan, methyl-benzotriazole, and chloro‑benzotriazole with sulfate radical (SO4·−) were determined for the first time. Experiments were conducted in buffered pure water, in buffered water added with the matrix substituents chloride, carbonate, NOM, and reverse osmosis concentrate with spiked micropollutants (MP). UV/persulfate eliminated all MP to a higher extent than ozonation in RO concentrates due to the higher yield of oxidative species and photolytic degradation. Compounds with electron-rich moieties such as carbamazepine, diclofenac, metoprolol, and sulfamethoxazole were completely eliminated with small ozone doses (< 0.5 mg O3 / mg DOC) and with a small fluence (< 5000 J m−2) in UV/persulfate processes. Photosensitive compounds with high reactivity towards hydroxyl radicals (·OH) and SO4·− like the x-ray contrast media Iopamidol, Iohexol, and Amidotrizoic acid were successfully eliminated with a reasonable fluence in UV/persulfate, whereas these compounds persist in ozonation at common ozone dosages. However, much higher fluences and ozone dosages were required for the least reactive compounds like the class of benzotriazoles. Comparing the application of both oxidative processes to the RO concentrate, ozonation has the disadvantage of forming bromate. The energy input of both processes strongly depends on the target compounds to be eliminated. For the elimination of compounds such as sulfamethoxazole, ozonation is a feasible technique, whereas UV/persulfate is better suited for the elimination of recalcitrant compounds such as x-ray contrast media. In general, oxidative process treatment of RO concentrate could be applied to partly abate micropollutants before discharge.

Removal characteristics of 53 micropollutants during ozonation, chlorination, and UV/H2O2 processes used in drinking water treatment plant

The removal of 53 emerging micropollutants (MPs), including 10 per- and polyfluorinated substances (PFASs), 25 pharmaceuticals and personal care products (PPCPs), 7 pesticides, 5 endocrine disrupters (EDCs), 3 nitrosamines, and 3 taste and odor compounds (T&Os), by chlorination, ozonation, and UV/H2O2 treatment was examined in deionized water and surface waters used as the raw waters in drinking water treatment plants (DWTPs) in South Korea. The UV/H2O2 treatment was effective in the removal of most MPs, whereas chlorination was selectively effective for 19 MPs, including EDCs (>70 %). MPs containing aromatic ring with electron-donating functional group, or primary and secondary amines were effectively removed by chlorination immediately upon reaction initiation. The removal of MPs by ozonation was generally lower than that of the other two processes at a low ozone dose (1 mg L−1), but higher than chlorination at a high ozone dose (3 mg L−1), particularly for 16 MPs, including T&Os. Compared in deionized water, the removals of MPs in the raw water samples were lower in all three processes. The regression models predicting the rate constants (kobs) of 53 MPs showed good agreement between modeled and measured value for UV/H2O2 treatment (R2 = 0.948) and chlorination (R2 = 0.973), despite using only dissolved organic carbon (DOC) and oxidant concentration as variables, whereas the ozonation model showed a variation (R2 = 0.943). Our results can provide the resources for determining which oxidative process is suitable for treating specific MPs present in the raw waters of DWTPs.

Integrated and Hybrid Processes for the Treatment of Actual Wastewaters Containing Micropollutants: A Review on Recent Advances

The global concern regarding the release of micropollutants (MPs) into the environment has grown significantly. Considerable amounts of persistent micropollutants are present in industrial discharges. Depending solely on a singular treatment approach is inadequate for the effective removal of MPs from wastewater due to their complex composition. The performance of different treatment methods to meet the discharge standards has been widely studied. These efforts are classified as hybrid and sequential processes. Despite their adequate performance, the optimization and industrial application of these methods could be challenging and costly. This review focuses on integrated (sequential) and hybrid processes for MP removal from actual wastewater. Furthermore, to provide a thorough grasp of the treatment approaches, the operational conditions, the source of wastewater containing MPs, and its characteristics are detailed. It is concluded that the optimal sequence to achieve the removal of MPs involves biological treatment followed by an advanced oxidation process (AOP) with a final passage through an activated carbon column. To refine this process further, a membrane unit could be added based on the desired effluent quality. Nevertheless, considering practical feasibility, this study identifies specific areas requiring additional research to implement this integrated treatment strategy effectively.

Effective removal of personal care product residues from aqueous media using hydrophobic deep eutectic solvents: Experimental and computational approach

Personal care product (PCP) residues - classified under micropollutants (MPs)- are widely found in aquatic environments, posing trace-level toxicity. Traditional water treatment techniques struggle to remove these toxins effectively. Deep eutectic solvents (DESs), the liquid mixtures typically composed of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs), have recently emerged as a viable alternative for extracting pollutants from water. Among DESs, hydrophobic deep eutectic solvents (HDESs) exhibit low water miscibility and unique solvent properties. The main objective of this study is to synthesize HDESs to effectively eliminate 2-naphthol and methylparaben- two of the significant chemical contaminants in PCPs- from aqueous media. HDESs were prepared by mixing different terpenes (menthol and thymol) and long-chain carboxylic acids at varying molar ratios. They were characterized using different spectroscopic and thermal techniques. The density and viscosity of the pure DESs were measured as afunction of temperature. Experimental studies were carried out using the liquid–liquid extraction (LLE) method, and the factors influencing the efficiency of extraction were optimized.Considering the limited number of studies on the extraction mechanism of MPs from aqueous media, this study employs comprehensive computational methods, including density functional theory (DFT) and the COnductor-like Screening MOdel for Real Solvents (COSMO-RS), to provide a detailed interpretation of the extraction mechanism. A series of successive extractions were conducted to reduce the DES usage to ensure economic viability. The reusability of the best-performed DES was explored. Additionally, the regeneration of one of the DESs was accomplished through activated carbon-based recovery.---------------------------------------------------------------------------------------------------------------------

Nanocomposite PVDF/TiO2 Photocatalytic Membranes for Micropollutant Removal in Secondary Effluent

In this study, a mixed-matrix method was used to prepare PVDF polymeric membranes with different amounts of TiO2 P25 photocatalyst embedded, which were employed in filtration processes in the presence of UV radiation (LED, peak emission at 375 nm) to eliminate two aqueous micropollutants (MPs) used as model compounds (venlafaxine and metoprolol). The obtained membranes were characterized to gain insights into their texture, morphology, composition, and other catalyst-related properties that could affect the photocatalytic filtration process. For that purpose, N2 adsorption–desorption, contact angle, SEM-EDX, thermal analysis, FTIR, XPS, UV-vis DRS, and PL spectroscopy were used. Filtration tests were carried out in continuous mode using a dead-end filtration cell to evaluate the performance of the prepared membranes in removing the selected MPs. Experiments were performed both in ultrapure water and a secondary effluent from a municipal wastewater treatment plant. It was found that the synthesized membranes could effectively remove the target MPs in ultrapure water, achieving up to 99% elimination. Such process performance decreased drastically in the secondary effluent with removals below 35%. Carbonate/bicarbonate ions in the secondary effluent were identified as the main scavenging substances. Thus, after the partial removal of carbonate/bicarbonate ions from the secondary effluent, the removal of MPs achieved was above 60%.

Retention of nine micropollutants covering a wide range of physical-chemical properties using polyelectrolyte multilayer hollow fiber NF membranes

Our work investigates the efficiency of two polyelectrolyte multilayer hollow fiber nanofiltration (NF) membranes for the removal of nine micropollutants (MPs) from pre-treated wastewater. The Square Latin method was used to select the contaminants to study according to their molecular weight, hydrophilicity (log Kow), and charge at environmental pH. NF experiments were carried out in batch mode at 20 °C with a crossflow velocity of 1 m.s−1, and a transmembrane pressure of 3 bar. Retentions of MPs and salts were evaluated at various volume reduction ratios (1, 3 or 6), membrane molecular weight cut-off (400 or 800 Da) and fouling potential of the matrix (ultrapure water, synthetic water, or real pre-treated wastewater). Our study identified the 400 Da membrane as the best option as balance between MPs and salts retention was the most acceptable. With this membrane, two thirds of the investigated MPs showed a retention above 90 %, two MPs had a retention around 60 % and only one MP was retained less than 20 % while monovalent salts had a retention lower than 30 %. Our work identified size exclusion and electrostatic interactions as the main mechanisms involved in MPs retention by the negatively charged membrane. This membrane showed its efficiency to maintain high permeation flux during 24 h-filtration of stream with organic matter content comparable to secondary-treated wastewater to a volume reduction ratio up to 6. At this content, organic matter did not modify retention of micropollutants or salts. The selected membrane is an encouraging tool to produce MPs-free water from pre-treated wastewater without producing a highly saline retentate. In the future, permeate would possibly be employed for REUSE purposes.

Tubular and bio-based carbons as binder-free gas diffusion electrodes for heterogeneous electro-Fenton to remove micropollutants

Heterogeneous electro-Fenton (HEF) coupled with anodic oxidation offers a plug-and-treat and chemical-free process over a wide range of pH values for removing recalcitrant micropollutants (MPs). This work introduces a self-standing and Fe-containing tubular carbon as a gas diffusion electrode (GDE) for HEF. Unlike planar Fe-containing carbon electrodes, as-synthesized carbons contain no fluorinated polymer as a subgroup of perfluoroalkyl and polyfluoroalkyl substances (PFAS), omitting the risk of secondary pollution due to undesired PFAS release during electrolysis. The implementation of GDE enables the increase of current densities up to 25mAcm−2, approaching relevant conditions for real-life applications. The altering pore structure on the gas channel side illustrates the possibility of minimizing GDE flooding without using hydrophobic and fluorinated polymers. GDEs without catalyst shows a specific H2O2 production rate of 3.6mgcm−2h−1 with a current efficiency of 56% at an applied current density of 8.5mAcm−2. Additionally, the Fe-containing GDE removes sulfamethoxazole (SMX) and carbamazepine (CBZ), revealing a declined degradation rate in a mixture, especially for a more recalcitrant pollutant such as CBZ. This work reveals the potential of as-synthesized self-standing tubular GDEs as PFAS-free electrodes for a decentralized and modular water treatment unit.

Differential biotransformation of micropollutants in conventional activated sludge and up-flow anaerobic sludge blanket processes

We report differential micropollutant biotransformations in a conventional activated sludge (CAS) process and a pilot-scale up-flow anaerobic sludge blanket (UASB) process operating in parallel at the same wastewater treatment plant.