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[Display omitted] • Electrochemically activated peroxymonosulfate (PMS) pretreatment was applied. • PMS pretreatment effectively removed dissolved organic carbon. • Electrochemical activation of PMS generated •OH directly. • Membrane fouling of membrane distillation was greatly mitigated by PMS pretreatment. • The one-time dosing mode of PMS was better for membrane fouling control. Membrane distillation (MD) provides a potential method to supply large volumes of good quality potable water from surface water resources, avoiding the risk of long-term water shortages. However, the high abundance of dissolved natural organic matter (DOM) in surface water induces severe membrane fouling, which reduces productivity and increases energy consumption. Therefore, for the first time, electrochemically activated peroxymonosulfate (PMS) treatment was applied prior to the direct contact (DC)-MD process with the aim of reducing the deposition of organics and inorganics on the membrane and reducing membrane fouling. Results showed that supplying PMS continuously at a rate of 0.10 mM/min, eliminated 30.4% of dissolved organic carbon (DOC). Furthermore, fluorescence parallel factor (PARAFAC) analysis showed that >60% of two fluorescent substances were removed after 60 min of the electrochemically activated PMS pretreatment at a current density of 5 mA/cm2. Electrochemical activation of PMS generated •OH directly, facilitating the removal and degradation of DOM. In terms of the DCMD performance, almost no normalized flux decline was observed for the DCMS process after 0.01 mM/min pre-oxidation, while 44.8% flux decay occurred in the standalone DCMD treating raw surface water. Compared with continuous dosing, the use of a one-time dosing mode achieved a better outcome, as more small organic molecules generated in continuous dosing mode are not conducive to membrane fouling control. Therefore, electrochemically activated PMS could be an effective tool to mitigate membrane fouling in MD processes, although the characteristics of membrane and feed should be considered. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photothermally-activated PMS pre-treatment was applied for MD fouling alleviation. • NOM in the surface water can be effectively removed after PMS pre-treatment. • Stable permeance (PMS (2 mM)) vs 50 % reduction (control) of flux were obtained. • •OH and SO 4 •− radicals generated by PMS contributed to the NOM removal. • The MD membrane properties could be kept conserved by the PMS pre-treatment step. Membrane distillation (MD) has demonstrated its efficacy for seawater desalination, which prompted researchers to investigate its performance for the treatment of surface water containing natural organic matter (NOM). However, membrane fouling remains a significant technological constraint in the acceptability and implementation of MD modules. Herein, for the first time, a photothermally-activated PMS pre-treatment process is coupled to a direct contact (DC)-MD module for effective membrane fouling control. Photothermally-activated PMS (2 mM) pre-treatment achieved 69 % of UV 254 removal and 30.9 % of dissolved organic carbon removal and allowed stable operation of the DCMD without any reduction in water permeance vs 50 % reduction obtained without the pretreatment step. The analysis of NOM fractions after pre-treatment using Parallel Factor Analysis and molecular weight distribution indicated changes in NOM composition, which facilitated membrane fouling control. The photothermally-activated PMS pre-treatment seems to alleviate membrane fouling by limiting the foulant-membrane interaction, which was observed to result in the formation of the fouling layer containing aromatic proteins, microbial byproducts-like substances, and inorganic (e.g., calcium) foulants. Finally, characterization of the used MD membranes revealed that the MD membrane properties could be kept unchanged by the photothermally-activated PMS pre-treatment step, thereby making the integrated DCMD system sustainable and attractive for widespread applications. [ABSTRACT FROM AUTHOR]

Nanomaterials (NMs) have received tremendous attention as emerging adsorbents for environmental applications. The ever-increasing release into aquatic systems and the potential use in water treatment processes heighten the likelihood of the interactions of NMs with aquatic dissolved organic matter (DOM). Once DOM is adsorbed on NMs, it substantially modifies the surface properties, thus altering the fate and transport of NMs, as well as their toxic effects on (micro)organisms in natural and engineered systems. The environmental consequences of DOM-NMs interaction have been widely studied in the literature. In contrast, a comprehensive understanding of DOM-NM complexes, particularly regarding the controlling factors, is still lacking, and its significance has been largely overlooked. This gap in the knowledge mainly arises from the complex and heterogeneous structures of the DOM, which prompts the urgent need to further characterize the DOM properties to deepen the understanding associated with the adsorption processes on NMs. This review aims to provide in-depth insights into the complex DOM adsorption behavior onto NMs, whether they are metal- or carbon-based materials. First, we summarize the up-to-date analytical methods to characterize the DOM to unravel the underlying adsorption mechanisms. Second, the key DOM characteristics governing the adsorption processes are discussed. Next, the environmental factors, such as the nature of adsorbents and solution chemistry, affecting the DOM-NM interactions, are identified and discussed. Finally, future studies are recommended to fully understand the chemical traits of DOM upon its adsorption onto NMs. Image 1 • Traditional and advanced analyses for DOM adsorption are fully reviewed. • Major factors to control DOM-NMs interactions are identified through literature review. • DOM properties governing DOM adsorption behaviors on NMs are highlighted. • Future studies are recommended of better understanding of DOM adsorption onto NMs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dopamine-functionalized PTFE (DA@PTFE) membranes were fabricated. • Membrane distillation (MD) performance of DA@PTFE membranes was investigated. • Secondary effluent from a WWTP was selected for MD to produce reclaimed water. • The DA-9@PTFE membrane demonstrated the best MD performance. • The water quality of MD permeate was significantly improved. Using secondary effluent from municipal wastewater treatment plants by membrane distillation (MD) to produce reclaimed water is an effective strategy for solving the growing global water shortage problems, however, membrane fouling caused by natural organic matter in the secondary effluent tends to reduce the water production rate of MD systems or destabilize these systems. Herein, the well-known dopamine (DA) surface functionalization method was applied and for the first time, DA-functionalized PTFE membranes (DA@PTFE) were fabricated to address the membrane fouling issue by treating secondary effluent enriched with effluent organic matter (EfOM) via direct contact membrane distillation (DCMD). The results showed that dopamine deposition formed a thin hydrophilic layer on the membrane surface, which inhibited the adhesion of contaminants and slowed down membrane fouling. The DA-9@PTFE membrane (with the C/F ratio of 1.25) demonstrated the best MD performance, with an increased flow rate of 13.8 % and much less membrane fouling compared with the pristine PTFE membrane (26.2 % vs. 56.8 % flux decay after three cycles). Meanwhile, using the DA@PTFE membranes in MD operation led to high water quality permeate, exhibiting a conductivity rejection rate above 99.6 % and a dissolved organic carbon retention rate above 90 %. This study demonstrates the good stability, wettability, and anti-pollution performance of DA@PTFE membranes in a DCMD system for real application in reclaimed water treatment. [ABSTRACT FROM AUTHOR]

• REM effectively removed fluorescence components in secondary effluent. • REM system showed consistent performance in repeated experiments. • FT-ICR MS confirmed extensive degradation/transformation of DOM on REM surface. • Highly unsaturated and phenolic compounds were transformed to the aliphatic. • Sulfur-containing molecular formulas were easily degraded. This research evaluated the performance of reactive electrochemical ceramic membrane (REM) in treating secondary effluent and investigated the fate of dissolved organic matter (DOM) at the molecular level. The role of adsorption, electrosorption, and oxidation in DOM removal was comprehensively elucidated based on fluorescence spectroscopy and high-resolution mass spectrometry (FT-ICR MS). Among the fluorescence components (C1-C3) in secondary effluent, microbial humic-like C2 showed fewer adsorption on the REM surface without applying an electrical potential. The electrosorption helped an enhanced uptake of all DOM components and transformed them onto the electrode surface. The fluorescence components and all three fractions (hydrophilic, transphilic, and hydrophobic) were rapidly degraded, and finished water with stable DOM was obtained. The leading degradation phenomena were the change of the unsaturated compounds to the aliphatic and transformation of large-sized molecules to medium and small-sized ones. Above 70% of the compounds in the secondary effluent acted as precursors, which were mineralized/degraded and transformed products were found on the REM surface and in the finished water. The compounds containing sulfur (CHOS) were easily and preferably degraded/mineralized, followed by the compounds containing nitrogen (CHON) and CHO. The oxidation of DOM led to the extensive formation of organo-chlorinated compounds, which contributed above 80% in products. Overall, the combination of fluorescence spectroscopy and FT-ICR MS provided unique behavior of DOM in the secondary effluent toward electro-oxidation in the REM system. These findings could help explore the potential of REM for different water matrices to project the possible composition of DOM in the finished water. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The green porous biochar aerogel (PBA) was facilely tuned for SGFPW pretreatment. • The optimal PBA adsorbed highest DOC ratio than other carbon materials reported. • PBAs adsorbed more humic substances, aromatic proteins, and hydrophobic organics. • Mechanism was electron-donor–acceptor, hydrophobic, and hydrogen-bond interactions. The complex organic compounds in shale gas flowback and produced water (SGFPW) pose threats to environmental safety and aggravate membrane fouling during membrane combined processes for SGFPW reuse. The high adsorption efficiency and capacity of aerogel revealed the tremendous potential for removing organics from SGFPW. In this study, we utilized a facile tuning method for porous biochar aerogel (PBA) to improve the adsorption performance of organic compounds in SGFPW as well as identified the adsorption mechanism by analyzing the organics characterization and PBAs' physicochemical properties. The PBAs were tailored by altering urea and KOH concentration, and the maximum adsorption removal (56.4%) and capacity (205.86 mg/g) of dissolved organic carbon (DOC) was obtained by the optimally tuned PBA-A11.5U12.0 (PBA tuned by 11.5 wt% KOH and 12.0 wt% urea) with a fast adsorption rate (0.012 g/(mg·min)), exceeding the DOC removal from shale gas wastewater by other carbon adsorbents reported. The characterization of organic compounds in SGFPW was identified by measuring fluorescence compounds and organic fractionation, which showed that the humic substances, aromatic proteins, and hydrophobic organics were much tended to be adsorbed by PBAs. Combined with principal component analysis, the organics adsorption mechanism was further identified, indicating the considerable contribution of electron-donor–acceptor interaction, hydrophobic effect, and hydrogen-bond formation. Such a high-efficiency tuned PBA showed decent adsorption performance for various SGFPW as well as good reusability. And it was fabricated from biopolymer with low cost, thus possessing promising prospects in SGFPW treatment. [ABSTRACT FROM AUTHOR]

• Higher chlorine consumption was noted during wet season in drinking water networks. • NDMA and NDMA-FP were found to increase with increase in length of distribution. • Humic-like component in finished water acted as a surrogate of residual chlorine. • Fluorescence peaks, I 245/410 and I 335/410 , correlated with chlorine consumption. • Fluorescence-based monitoring could help in adjusting chlorine dosage. Several factors play a role in chlorine consumption in drinking water networks such as microbial contamination and dissolved organic matter (DOM). This study investigated the simultaneous impacts of seasonal variations on chlorine consumption and DOM composition for a year-long period in three different full-scale water distribution networks in a southern city of China. Efforts were made to determine the association between different fluorescence moieties in DOM of finished water and chlorine consumption through excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC). The chlorine consumption was also found to be directly related to N -Nitrosodimethylamine (NDMA) and NDMA-formation potential (NDMA-FP), presenting consequence of excess residual chlorine. The wet season with high rainfall showed elevated consumption of chlorine on the opposite of dry season. During wet season, humic-like component in finished water was dominant than protein-like features and its abundance decreased in dry season. Results proved that chlorine consumption was season dependent and highly influenced by DOM composition in the finished water. Unlike the bulk quality parameters and protein-like component, fluorescence moieties related to humic substances acted as a surrogate for the chlorine consumption. Based on humic-like component, a single excitation based fluorescence peak, I 245/410 or I 335/410 , was also extracted from EEMs of finished water samples and validated on different water distribution networks. These two single peaks well-explained the trends of residual chlorine and have the potential for on-line monitoring and portable purposes. This field-based study demonstrated application of fluorescence spectroscopy in designing chlorine dose to obtain optimal residual chlorine at consumer's tap. [ABSTRACT FROM AUTHOR]

This study aims to extend and demonstrate the application of fluorescence spectroscopy for monitoring the water quality of three differently operated full-scale drinking water treatment plants located in the Shenzhen city (China). A ratio of fluorescent dissolved organic matter (FDOM), which describes relative changes in humic-like to protein-like fluorescence, was used to explain mechanisms behind the physicochemical processes. The fluorescence components obtained through individual and combined parallel factor analysis (PARAFAC) modeling revealed the presence of humic-like (C1) and protein-like (C2) structures in the DOM. The C1/C2 ratio provided a direct relationship between the seasonal variations and DOM composition. Wet season generated DOM enriched with humic-like fluorescence, while dry season caused a higher release of protein-like fluorescence. The fluorescence ratio presented unique patterns of DOM in treatment trains. The chemical pretreatment and disinfection unit processes showed a higher tendency to remove the humic-like fluorescence. However, the C1/C2 ratio increased during physical treatment processes such as coagulation-precipitation and sand filtration, indicating preferential removal of protein-like fluorescence. The DOM composition in influent directly (R2 = 0.77) influenced the relative intensities of fluorescence components in the treated water. Compared to the dry season, the wet season caused significant changes in DOM composition and produced treated water enriched with humic-like fluorescence. This fluorescence ratio offers an approach to explore the role of different treatment units and determine the factors affecting the composition of DOM in the surface water and drinking water treatment plants. Image 1 • C1/C2 (humic-like/protein-like) was directly influenced by seasonal variations. • Wet season produced DOM enriched with humic structures. • Dry season caused higher release of protein-like fluorescence. • Chemical pretreatments units preferentially removed humic-like fluorescence. • Protein-like fluorescence was more prone to be removed in physical treatment units. [ABSTRACT FROM AUTHOR]

N -nitrosamines have been identified as emerging contaminants with tremendous carcinogenic potential for human beings. This study examined the seasonal changes in the occurrence of N -nitrosamines and N -nitrosodimethylamine formation potential (NDMA-FP) in drinking water resources and potable water from 10 drinking water treatment plants in a southern city of China. The changes in N -nitrosamines are well correlated with dissolved organic matter (DOM), particularly fluorophores, which were measured and compared between traditional fluorescence indices and excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC). Four of N -nitrosamine species including N -nitrosodimethylamine (NDMA), N -Nitrosodibutylamine (NDBA), N -Nitrosopyrrolidine (NPYR), and N -Nitrosodiphenylamine (NDPhA) are found to be abundant compounds with an average of 29.5% (26.7%), 20.0% (25.2%), 18.9% (16.0%), and 9.0% (9.9%) in the source (and treated) water, respectively. The sum of N -nitrosamines concentration is recorded to be low in the wet season (July–September), whereas the dry season (October–December) provided opposite impacts. EEM-PARAFAC modeling indicated the predominance of humic-like component (C1) in the wet season while in the dry season the water was dominant in protein-like component (C2). All the N -nitrosamines excluding NDPhA and N -Nitrosomorpholine (NMOR) showed a strong association with protein-like component (C2). In contrast, humic-like C1, which was directly influenced by rainfall, was found to be a suitable proxy for NMOR and NDPhA. The results of this study are valuable to understand the correlation between different N -nitrosamines and DOM through adopting fluorescence signatures. Image 1 • The mean concentration of each N -nitrosamine in drinking water is below 5 ng/L. • Sum of N -nitrosamines in drinking water is higher in dry season than wet season. • Humic-like component shows higher intensity in wet season. • Most of N -nitrosamines associate with protein-like component. • Compare to HIX and BIX, EEM-PARAFAC provides better proxies for N -nitrosamines. [ABSTRACT FROM AUTHOR]

The combined pretreatment of coagulation and ozonation is extensively adopted for water quality enhancement and membrane fouling reduction in wastewater reclamation. Herein, the integrated treatment of ferrate pretreatment and in-situ ozonation/ceramic membrane filtration on water quality improvement and fouling reduction of ceramic membrane in secondary wastewater effluent treatment was reported for the first time. The results showed that the hybrid treatment of ferrate pretreatment and in-situ ozonation greatly inhibited the generation of N-dimethyl nitrosamine (NDMA) and did not generate bromate. Meanwhile, the best removal efficiencies of low molecular weight (MW) organics (32.3%), humic-like substances (17.8%) and biopolymers (87.5%) in effluent were achieved by the combination of ferrate (0.15 mM) pretreatment and in-situ ozonation (10 mg/L). Moreover, the control sample (without any treatment) had a fouling transmembrane pressure (TMP) of 30.5 kPa after 7.0 h filtration under a constant flux of 90 L/(m2·h) while that was only 1.0 kPa by the hybrid treatment of ferrate (0.15 mM) pretreatment and in-situ ozonation (10 mg/L). Soluble microbial products (SMP)-like substances with high molecular weight (MW) of 20–2000 kDa were the main foulants and intermediate-standard fouling mechanism played a principal role during the membrane filtration process. Statistical analysis showed that dissolved organic carbon (DOC), UV 254 and protein had the greatest positive correlation (above 0.92) to the total fouling resistance, whilst turbidity displayed the greatest negative correlation (around −0.61) to the total fouling resistance. The remarkable fouling alleviation was due to the improved water quality and in-situ cleaning, which were contributed to the coagulation and oxidation by ferrate and in-situ ozonation. Image 1 • Ferrate pretreatment- in-situ ozonation greatly reduces ceramic membrane fouling. • NDMA and bromate are remarkably reduced by ferrate pretreatment- in-situ ozonation. • Intermediate-standard fouling is the main fouling mechanism. • DOC, UV 254 and protein are the most important positive factors to R t. • Fouling alleviation is due to the improved water quality and in-situ cleaning. [ABSTRACT FROM AUTHOR]