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With growing concerns regarding the ecological and human risks of organic micropollutants (OMPs) in water, much effort has been devoted worldwide to establishing quality standards and compiling candidate and watch lists. Although bank filtration is recognized as an efficient natural water treatment in the removal of contaminants such as OMPs, the increase in exploitation requires continuous assessment of removal efficiency. This review aims to provide a critical overview of bank filtration (BF) reports on more than a hundred priority substances (PSs) and compounds of emerging concern (CECs) listed in the relevant European Union regulations. Field- and lab-scale studies analyzing the removal efficiency and its variance of individual OMPs and biological indicators using BF and the main influencing factors and their interactions, shortcomings, and future challenges are discussed in this review. The removal efficiency of EU-relevant contaminants by BF has been comprehensively investigated for only a few pollutants listed in the environmental EU regulations: pharmaceutically active compounds, (e.g., the anti-inflammatory drug diclofenac, some antibiotics (e.g. , sulfamethoxazole and trimethoprim)), a few pesticides (e.g. , atrazine), and faecal indicators such as Escherichia coli. In many cases, the measured concentrations of PSs and CECs have not been published numerically, which hinders comprehensive statistical analysis. Although BF is one of the most cost-effective and efficient water treatments, present field and lab studies have demonstrated the diversity of site-specific factors affecting its efficiency. Even in the case of substances known to be removed by BF, the efficiency rates can vary with environmental and anthropogenic factors (e.g. , hydrogeological parameters and the contamination level of infiltrating water) and abstraction well parameters (e.g. , the depth, distance, and pumping volume). The published removal rate variations and influencing factors often reflect the research design (field or lab-scale), which can lead to ambiguities. [Display omitted] • BF efficiency varies with environmental, anthropogenic, and well properties. • The concomitant influencing factors make the analysis complex. • The methodological heterogeneity in BF studies hinders their comparison. • Removal rate variations often reflect the research design. • Anthropogenic impact on BF efficiency requires further study. [ABSTRACT FROM AUTHOR]

The combination of photocatalysis with membrane separation technology allows to mitigate potential membrane fouling while degrading the organic micropollutants in water. This work is focused on the immobilization of a g-C 3 N 4 promising photocatalyst, in the form of a g-C 3 N 4 -PVDF polymeric membrane, for the elimination of representative pharmaceutical substances from complex water matrices in a continuous flow mode under visible light irradiation. Metoprolol (MTP), venlafaxine (VEN) and diclofenac (DCF) in a mixture (at 250 μg L−1 each) were fed to the system at room temperature. The adsorption of these substances on the membrane was negligible (< 5%) in the dark. Removals of 89%, 92% and 72% for MTP, VEN and DCF, respectively, were achieved in deionized water using visible-light emitting diodes (LEDs) as light source. Moreover, the permeate flux remained constant throughout the experiments (89.5 L m−2 h−1). The membrane system was then assessed using urban wastewater treatment plant effluent, surface and tap waters, spiked with the target analytes. As expected, a worse performance was observed with these matrices, although still high removals were achieved in tap water (73%, 61% and 75%, respectively for MTP, VEN and DCF). Accordingly, the impact of the occurrence of humic acid as representative species of natural organic matter, as well as inorganic ions such as chlorides, sulphates, phosphates and carbonates, was evaluated in more detail. Clearly, humic acid and sulphates were the most impactful on the treatment performance. Finally, different scavengers were used to understand the photocatalytic mechanism, suggesting that superoxide radicals and photogenerated holes were the main active species involved in the removal of the studied micropollutants. [Display omitted] • g-C 3 N 4 -PVDF membrane was successfully applied for continuous micropollutant removal. • High pharmaceutical removal yields were achieved in deionized water with constant flux. • Less effective performance in real water matrices but still high activity in tap water. • Humic acid and sulphates had significant negative impact on treatment performance. • Superoxide radicals and photogenerated holes are behind the photocatalytic mechanism. [ABSTRACT FROM AUTHOR]

This work demonstrates the suitability of employing carbon-based catalytic membranes for persulfate activation and water disinfection in continuous flow mode of operation for the first time. Poly(vinylidene fluoride) (PVDF) membranes with and without nitrogen-doped reduced graphene oxide (rGO-M) were prepared and tested. The cumulative effect of each membrane component was assessed based on the persulfate activation capacity and the retention and/or elimination of faecal contamination indicator microorganisms in a defined suspension of Escherichia coli and Enterococcus faecalis. In the absence of persulfate, the pristine PVDF membrane enabled retention of 1.98 ± 0.51 log, while the rGO-M–PVDF membrane removed 3.71 ± 0.66 log of the initial microbial abundance (3.87 ± 0.01 log) after 6 h of operation. The catalytic features of the rGO-M–PVDF membrane were then demonstrated by adding a persulfate precursor to the feed suspension. This treatment system was able to reduce the abundance of cultivable microorganisms (total heterotrophs, enterobacteria, enterococci) of the defined suspensions and river water samples to values below the limit of detection (< 0.5 CFU mL−1) up to 24 h operation. In addition, the reactivation capacity of the cultivable microorganisms and representative specific genes (16S rRNA, intl 1, bla TEM and sul 1) after 7-day storage of the treated river water was studied. Among the parameters analysed, only total cultivable heterotrophic cells were able to regrow to values similar to those found in the feed. Therefore, the proposed system can be considered as a promising technology for the removal of harmful microbiota during drinking water production in continuous flow mode. [Display omitted] • Nitrogen-doped reduced graphene oxide (rGO-M–PVDF) membranes were produced. • The rGO-M–PVDF membranes activated persulfate in a continuous flow mode treatment. • River water was disinfected to safe levels in continuous flow mode (24 h operation). • The treated river water maintained microbiological stability upon 7-day storage. [ABSTRACT FROM AUTHOR]

Powdered catalysts are commonly used in lab-scale tests for the catalytic reduction of oxoanions in drinking water, but their powder nature limits their application at full scale. In this work, Pd and Pd-Cu catalysts (5% wt.) supported on carbon materials with different structural properties, in powder form, were used to prepare catalytic membranes that were tested in a reactor with flow-through configuration (FTCMR) to study their performance in the reduction of NO 3 -, NO 2 - and BrO 3 -. Pd catalytic membranes showed high activity in the reduction of NO 2 -, being the selectivity to NH 4 + lower than 2% at 80% NO 2 - conversion in all cases. In BrO 3 - reduction, they exhibited a wide range of conversions being the catalyst supported on materials with high conductivity the most active ones, which may be ascribed to the charge distribution at the metal-carbon interface. NO 3 - reduction using Pd-Cu catalytic membranes showed that catalysts supported on materials with small nanoparticle size and low electrical conductivity exhibited higher selectivity to NH 4 +. FTCMR led to a good control of H 2 transfer and availability in the active sites, facilitating the tuning of H 2 availability conditions to preserve the activity, while maintaining/diminishing selectivity to NH 4 +. In simultaneous oxoanions reduction tests, NO 3 - reduction was inhibited by Br species, probably by affection of the Pd-Cu redox cycle. This fact could be crucial to the future development of drinking water treatment processes, as conditions the order of the disinfection and NO 3 - reduction steps. • Pd- and Pd-Cu-based catalytic membranes were active in the reduction of oxoanions. • FTCMR led to a good control of H2 transfer and availability in the active sites. • NO3- reduction was inhibited by Br species, probably affecting the Pd-Cu redox cycle. [ABSTRACT FROM AUTHOR]

Demineralized and disinfected waters may have very low microbial loads, requiring that large volumes of water are filtered to recover enough biomass for further analysis. Extended filtration periods, often interrupted by clogging, are a major limiting factor to concentrate samples' microbiota for further examination, besides hindering the work pace. In this study, we investigated the performance of three types of filtering membranes – polycarbonate (PC), cellulose nitrate (CN), and polyethersulfone (PES) with 0.22 µm pore size for culture-independent microbiological analysis (quantitative PCR of seven housekeeping and integrase genes) of tap water, recirculating tap water in a bottle washing loop, and of demineralized water. Compared to PC membranes, CN or PES required lower filtration periods, although had slightly lower DNA extraction yields. However, genes abundance per volume of water was, in general, not significantly different. The exception was observed for bottle washing water in which PC membranes supported significantly higher quantification values than PES membranes. These differences were lower than ∼ 0.5 log-units and did not hamper the distinction of the types of water based on genes profile. Also, the type of membrane did not significantly affect the profile of the bacterial community determined for tap and demineralized water. A major conclusion is that CN membranes, cheaper, allowing shorter filtration periods, and producing results that are not significantly different from those obtained with PC or PES, can be a good alternative to analyze waters with low biomass loads. [Display omitted] • The performance of PC, CN, and PES filters to retain bacterial cells was compared. • Lower vacuum-filtration times were achieved with CN and PES than with PC filters. • DNA yields were slightly lower with CN and PES than with PC filters. • Filter type did not impact gene quantification in clean water samples. • Bacterial community profile was not significantly affected by the filter type. [ABSTRACT FROM AUTHOR]

Progress on the development and performance of graphene-based catalytic membranes for water treatment applications, particularly using advanced oxidation technologies (AOTs), is the subject of this review. A detailed search on Scopus database provided 79 studies concerning catalytic membranes made up of graphene derivatives for water treatment applications, namely for the effective removal of aqueous organic contaminants by photocatalysis, electrocatalysis and persulfate/peroxymonosulfate activation catalysis. The main goal of this review is the analysis of the existing studies dealing with graphene-derived catalytic membranes for water treatment, in particular assessing information of: i) membrane fabrication approaches, ii) target pollutants, and iii) graphene production methods. From a critical point of view, 60 studies (76%) evaluated the membrane performance towards the degradation of dyes, which are easily removed by most of the typical catalytic oxidation reactions. Most publications refer to the use of Hummers'-derived graphene analogues (59 studies, or ~75%) and vacuum filtration (33 studies, or 44%) as the chosen catalytic carbon material and membrane fabrication procedure, respectively. Fifty-six studies (71%) evaluated membrane performance under filtration mode, while the other 23 reports (29%) focused on batch mode of operation, which is far from the reality of a full-scale membrane filtration process. Moreover, various authors proposed the generation of reactive oxygen species (ROS), such as HO•, O 2 •−, among others, in the removal of several contaminants. Additional research is still needed, concerning cost-analysis of the processes, the possible reactivity of graphene-based membranes with ROS (i.e. understanding how to preserve long-term membrane stability) and using real water matrices. ga1 • Graphene derived catalytic membranes are effective water treatment options. • Photocatalysis, PS/PMS activation and electrocatalysis are the most employed AOTs. • Membrane fabrication, target pollutants and graphene production methods are discussed. • Research using real water matrices is needed. • Possible membrane reactivity with generated ROS should be investigated. [ABSTRACT FROM AUTHOR]

Photocatalytic ozonation was employed for the first time in continuous mode with TiO 2 -coated glass Raschig rings and light emitting diodes (LEDs) to treat urban wastewater as well as surface water collected from the supply area of a drinking water treatment plant (DWTP). Different levels of contamination and types of contaminants were considered in this work, including chemical priority substances (PSs) and contaminants of emerging concern (CECs), as well as potential human opportunistic antibiotic resistant bacteria and their genes (ARB&ARG). Photocatalytic ozonation was more effective than single ozonation (or even than TiO 2 catalytic ozonation) in the degradation of typical reaction by-products (such as oxalic acid), and more effective than photocatalysis to remove the parent micropollutants determined in urban wastewater. In fact, only fluoxetine, clarithromycin, erythromycin and 17-alpha-ethinylestradiol (EE2) were detected after photocatalytic ozonation, by using solid-phase extraction (SPE) pre-concentration and LC-MS/MS analysis. In surface water, this treatment allowed the removal of all determined micropollutants to levels below the limit of detection (0.01–0.20 ng L −1 ). The efficiency of this process was then assessed based on the capacity to remove different groups of cultivable microorganisms and housekeeping (16S rRNA) and antibiotic resistance or related genes ( intI1, blaTEM , qnrS , sul1 ). Photocatalytic ozonation was observed to efficiently remove microorganisms and ARGs. Although after storage total heterotrophic and ARB (to ciprofloxacin, gentamicin, meropenem), fungi, and the genes 16S rRNA and intI1 , increased to values close to the pre-treatment levels, the ARGs ( blaTEM , qnrS and sul1 ) were reduced to levels below/close to the quantification limit even after 3-days storage of treated surface water or wastewater. Yeast estrogen screen (YES), thiazolyl blue tetrazolium reduction (MTT) and lactate dehydrogenase (LDH) assays were also performed before and after photocatalytic ozonation to evaluate the potential estrogenic activity, the cellular metabolic activity and the cell viability. Compounds with estrogenic effects and significant differences concerning cell viability were not observed in any case. A slight cytotoxicity was only detected for Caco-2 and hCMEC/D3 cell lines after treatment of the urban wastewater, but not for L929 fibroblasts. [ABSTRACT FROM AUTHOR]