Fate of Naturally Dissolved Organic Matter and Synthetic Organic Compounds Subjected to Drinking Water Treatment Using Membrane, Activated Carbon, and UV/H2O2 Technologies.

Organic pollutants are toxic and are present in drinking water. The conventional processes of most water plants can basically meet the discharge standard. However, based on the improvement of the objective of organic pollutants control and the constant change of water characteristics, the results may not be ideal. This study evaluates the effectiveness of different treatments such as microfiltration, nanofiltration, reverse osmosis, activated carbon, and ultraviolet irradiation/H2O2 in terms of the removal of organic pollutants. Among the DOM results, nanofiltration, reverse osmosis, and activated carbon showed optimal performance due to the characteristics of processes and the compound properties. However, the risks of low-molecular-weight organic residue and byproduct formation are still present. Thirty-nine species of synthetic organic compounds (SOC) were qualitatively and semiquantitatively analyzed. Different technologies showed varying removal capabilities for SOC based on their properties and many substances coexisted leading to abnormal removal performances. These residual organics showed the characteristics of lower molecular weight, more hydrophilicity, further unknown impacts, and with risk of DBPs. Based on the above insights, possible methods can be rationally chosen for on-demand decontamination of organics in unconfined aquatic environment and long-time impact on water characteristics and human health also should be considered.

Dose-Response Behavior of Pathogens and Surrogate Microorganisms across the Ultraviolet-C Spectrum: Inactivation Efficiencies, Action Spectra, and Mechanisms.

The dose-response behavior of pathogens and inactivation mechanisms by UV-LEDs and excimer lamps remains unclear. This study used low-pressure (LP) UV lamps, UV-LEDs with different peak wavelengths, and a 222 nm krypton chlorine (KrCl) excimer lamp to inactivate six microorganisms and to investigate their UV sensitivities and electrical energy efficiencies. The 265 nm UV-LED had the highest inactivation rates (0.47-0.61 cm2/mJ) for all tested bacteria. The bacterial sensitivity strongly fitted the absorption curve of nucleic acids at wavelengths of 200-300 nm; however, indirect damage induced by reactive oxygen species (ROS) was the leading cause of bacterial inactivation under 222 nm UV irradiation. In addition, the guanine and cytosine (GC) content and cell wall constituents of bacteria affect inactivation efficiency. The inactivation rate constant of Phi6 (0.13 ± 0.002 cm2/mJ) at 222 nm due to lipid envelope damage was significantly higher than other UVC (0.006-0.035 cm2/mJ). To achieve 2log reduction, the LP UV lamp had the best electrical energy efficiency (required less energy, average 0.02 kWh/m3) followed by 222 nm KrCl excimer lamp (0.14 kWh/m3) and 285 nm UV-LED (0.49 kWh/m3).

Molecular ecological networks reveal the spatial-temporal variation of microbial communities in drinking water distribution systems.

Microbial activity and regrowth in drinking water distribution systems is a major concern for water service companies. However, previous studies have focused on the microbial composition and diversity of the drinking water distribution systems (DWDSs), with little discussion on microbial molecular ecological networks (MENs) in different water supply networks. MEN analysis explores the potential microbial interaction and the impact of environmental stress, to explain the characteristics of microbial community structures. In this study, the random matrix theory-based network analysis was employed to investigate the impact of seasonal variation including water source switching on the networks of three DWDSs that used different disinfection methods. The results showed that microbial interaction varied slightly with the seasons but was significantly influenced by different DWDSs. Proteobacteria, identified as key species, play an important role in the network. Combined UV-chlorine disinfection can effectively reduce the size and complexity of the network compared to chlorine disinfection alone, ignoring seasonal variations, which may affect microbial activity or control microbial regrowth in DWDSs. This study provides new insights for analyzing the dynamics of microbial interactions in DWDSs.

The impact of UV treatment on microbial control and DBPs formation in full-scale drinking water systems in northern China.

To manage potential microbial risks and meet increasingly strict drinking water health standards, UV treatment has attracted increasing attention for use in drinking water systems in China. However, the effects of UV treatment on microbial control and disinfection by-products (DBPs) formation in real municipal drinking water systems are poorly understood. Here, we collected water samples from three real drinking water systems in Beijing and Tianjin to investigate the impacts of UV treatment on microbial control and DBP formation. We employed heterotrophic plate count (HPC), flow cytometry (FCM), quantitative PCR analysis, and high-throughput sequencing to measure microorganisms in the samples. Different trends were observed between HPC and total cell count (measured by FCM), indicating that a single indicator could not reflect the real degree of biological re-growth in drinking water distribution systems (DWDSs). A significant increase in the 16S rRNA gene concentration was observed when the UV system was stopped. Besides, the bacterial community composition was similar at the phylum level but differed markedly at the genera level among the three DWDSs. Some chlorine-resistant bacteria, including potential pathogens (e.g., Acinetobacter) showed a high relative abundance when the UV system was turned off. It can be concluded that UV treatment can mitigate microbial re-growth to some extent. Finally, UV treatment had a limited influence on the formation of DBPs, including trihalomethanes, haloacetic acids, and nitrogenated DBPs. The findings of this study may help to understand the performance of UV treatment in real drinking water systems.

Enhanced permeation performance of biofiltration-facilitated gravity-driven membrane (GDM) systems by in-situ application of UV and VUV: Comprehensive insights from thermodynamic and multi-omics perspectives.

Biofouling is a major challenge limiting the practical application of biofiltration-facilitated gravity-driven membrane (GDM) systems in drinking water treatment. In this study, ultraviolet irradiation, including ultraviolet (UV) and vacuum ultraviolet (VUV) irradiation, was used for in-situ purification of membrane tanks to control membrane biofouling. After using UV and VUV, the permeate flux increased significantly by 26.1% and 78.3%, respectively, which was mainly due to the decreased cake layer resistance (Rc). The permeability of the biofouling layer improved after UV and VUV application, as evidenced by the increased surface porosity and decreased thickness. The contents of loosely bound extracellular proteins (LB-PN) and tightly bound extracellular proteins (TB-PN) in the biofouling layer were reduced after UV and VUV irradiation. The decreased LB-PN and TB-PN improved the interfacial free energy between the fouling itself and between the fouling and the membrane, which contributed to the reduction of interfacial cohesion and adhesion, resulting in a looser and thinner biofouling layer and a cleaner membrane. The concentration of protein-like material in the membrane tank decreased after UV and VUV irradiation, significantly altering the bacterial community structure on the membrane surface (Mantel's r > 0.7, p < 0.05). The changes in the metabolic state were responsible for the differences in the LB-PN and TB-PN contents. The inhibition of "Alanine, aspartate and glutamate metabolism" and "Glycine, serine and threonine metabolism" reduced amino acid biosynthesis, which restricted the secretion of LB-PN and TB-PN. Critical genera in the Proteobacteria phylum, such as Hirschia, Rhodobacter, Nordella, Candidatus_Berkiella, and Limnohabitans, were involved in metabolite transformation. Overall, the in-situ application of UV and VUV can be an effective alternative strategy to mitigate membrane biofouling, which would facilitate the practical application of biofiltration-facilitated GDM systems in drinking water treatment.

Antibiotics degradation by UV/chlor(am)ine advanced oxidation processes: A comprehensive review.

Antibiotics are emerging contaminants in aquatic environments which pose serious risks to the ecological environment and human health. Advanced oxidation processes (AOPs) based on ultraviolet (UV) light have good application prospects for antibiotic degradation. As new and developing UV-AOPs, UV/chlorine and derived UV/chloramine processes have attracted increasing attention due to the production of highly reactive radicals (e.g., hydroxyl radical, reactive chlorine species, and reactive nitrogen species) and also because they can provide long-lasting disinfection. In this review, the main reaction pathways of radicals formed during the UV/chlor (am)ine process are proposed. The degradation efficiency, influencing factors, generation of disinfection by-products (DBPs), and changes in toxicity that occur during antibiotic degradation by UV/chlor (am)ine are reviewed. Based on the statistics and analysis of published results, the effects caused by energy consumption, defined as electrical energy per order (EE/O), increase in the following order: UV/chlorine < UV/peroxydisulfate (PDS)< UV/H2O2 < UV/persulfate (PS) < 265 nm and 285 nm UV-LED/chlorine (EE/O). Some inherent problems that affect the UV/chlor (am)ine processes and prospects for future research are proposed. The use of UV/chlor (am)ine AOPs is a rich field of research and has promising future applications, and this review provides a theoretical basis for that.

Can we shape microbial communities to enhance biological activated carbon filter performance?

A new focus on biofiltration has emerged that aims to shape microbial communities to improve treatment efficacy. It is therefore necessary to understand the linkages between microbial community structure and biofilter function. However, the assembly and interaction of microbial communities in biological activated carbon (BAC) filters are unknown. In this study, we selected one coal-based granular activated carbon (GAC), GAC-13, with simultaneously developed micropore and micro-level macropore volume used for a bench-scale BAC column experiment, and compared it with other coal-based GACs and wood-based GAC in terms of the dissolved organic carbon (DOC) removal and microbial community characteristics. The results showed that there was no difference between the DOC removal efficiency of BAC-13 and the other two coal-based BAC filters with high iodine value in the period dominated by adsorption, while the DOC removal efficiency of BAC-13 (64.7±0.6%) was significantly higher than that of other BAC filters (36.3±0.8-54.1±0.4%) with a difference of 0.3-0.7 mg/L in DOC during the steady state. The bacterial communities were strongly assembled by deterministic rather than stochastic factors, where the surface polarity of GAC had a greater effect on the microbial communities than its physical properties. The corresponding co-occurrence network revealed that microbes in the BAC filter may be more cooperative than competitive. The keystone bacterium Hyphomicrobium, which had a relatively low abundance, contributed 0.3-1% more to the most abundant functions and produced 5-21 proteins/(g·GAC) more than the dominant bacterium Sphingobium. The metaproteomic-based approach could provide more accurate information regarding the contributions of different species to metabolic functions. The pore size distribution of GAC was found to be an important factor in determining BAC filter performance; the most important pore sizes were micropores and micro-level macropores (0.2-10 µm and >100 µm in diameter), and the latter impacted the abundance of keystone species. Overall, our findings provide new insights into shaping microbial communities by optimizing pore size structure to improve BAC performance, especially the abundance of keystone species.

Contribution of filtration and photocatalysis to DOM removal and fouling mechanism during in-situ UV-LED photocatalytic ceramic membrane process.

The use of ceramic membranes and ultraviolet light-emitting diodes (UV-LEDs) has advanced the application of photocatalytic membrane for water treatment. We systematically evaluated the contribution of filtration and photocatalysis to dissolved organic matter (DOM) removal and fouling mechanism during in-situ UV-LED photocatalytic ceramic membrane filtration. The results showed that physical rejection primarily led to removal of 4-15 kDa molecules and photocatalysis further increased the removal of 1-4 kDa molecules, causing small sized microbial humic-like or protein-like materials in the permeate. In-situ UV-LED photocatalysis had an excellent effect on membrane fouling mitigation regardless of DOM sources. The dominant fouling mechanism changed from partial blockage to gel layer formation with increasing Ca2+ concentration but did not change with UV treatment. Correlation analysis revealed that the removal of 1-4 kDa molecules contributed to the mitigation of both reversible and irreversible fouling resistance, and the small molecules were the major cause of irreversible fouling resistance. Removal of 1-4 kDa terrestrial humic acid-like contributed to the pore blockage mechanism for synthetic water. Removal of 4-15 kDa protein-like materials was closely correlated to the pore blockage mechanism for real water. Trihalomethanes (THMs) and haloacetic acids (HAAs) formation potential (FP) were both significantly reduced after photocatalytic ceramic membrane process, but precursors of nitrogenous disinfection by-products (N-DBPs) with high toxicity were not removed by filtration or by photocatalysis, which deserves attention. Membrane rejection made higher contribution to better DBPFP control than photocatalysis. This study provides novel insights into the impact of UV-LED on DOM removal, DBPFP control and fouling mitigation, promoting the development of photocatalytic ceramic membrane filtration.

Insight into the degradation of ciprofloxacin by medium-pressure UV-activated monochloramine process.

The degradation efficiency and mechanisms of ciprofloxacin (CIP), a typical antibiotic, by a medium-pressure ultraviolet/chloramine (MPUV/NH2Cl) treatment were investigated. The results showed that CIP degradation by MPUV/NH2Cl was significantly higher than that by NH2Cl oxidation and MPUV photolysis, and that this degradation processes were consistent with pseudo-first-order kinetics. The initial CIP concentration (7.5-30.2 µM) and the presence of HCO3- (0.5-10 mM) significantly inhibited CIP degradation with kobs,CIP 0.0090-0.0069 and 0.0078-0.0048 cm2/mJ. In contrast, NO3- (50-500 µM) and Br- (0.5-10 mM) significantly promoted the degradation with kobs,CIP 0.0078-0.0102 and 0.0078-0.0124 cm2/mJ. The effect of Cl- (0.5-10 mM) and natural organic matter (1-5 mg/L) were negligible. The NH2Cl dosage (30-60 µM) presented a dual effect, in which its increase within the optimal concentration range (30-40 µM) accelerated CIP degradation due to the formation of reactive radicals, whereas an excessive increase (40-60 µM) quenched the free radicals, ultimately quenching the free radicals and inhibiting the degradation. The optimum pH for CIP degradation under MPUV/NH2Cl treatment was 7.0. The contribution of reactive halogen species (i.e., reactive chlorine species and reactive nitrogen species) to CIP degradation was substantially greater than that of hydroxyl radicals under acidic or neutral conditions. We identified the degradation products of CIP and proposed degradation pathways, which included defluorination and cracking of the piperazine ring, with the latter being dominant. Compared to haloacetic acid (HAA) and nitrogenous disinfection byproducts (N-DBPs), MPUV/NH2Cl significantly reduced trihalomethane (THM) production and theoretical cytotoxicity by 80.1% and 78.4% respectively, compared to the background experiment in natural water at a UV dose of 300 mJ/cm2.

Degradation and transformation of norfloxacin in medium-pressure ultraviolet/peracetic acid process: An investigation of the role of pH.

Given that fluoroquinolone antibiotics (FQs) are frequently detected in aquatic environments, there is an urgent need for the development of efficient water treatment technologies for their removal. Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have increasingly attracted attention as promising technologies for water decontamination in this regard. In this study, a novel PAA-based AOP (the medium-pressure ultraviolet (MPUV)/PAA process) was employed to degrade norfloxacin (NOR), which is an extensively applied FQ that is widely present in water. Mechanistic and kinetic aspects of the role of pH on this NOR degradation process were investigated. The results obtained showed that the MPUV/PAA process could effectively degrade NOR (pH = 5-9), and the degradation efficiency was significantly enhanced at pH 7 and 9 compared with that at pH 5. This observation could be attributed to the effect of pH on the ionic forms of NOR and the generation of reactive oxygen species (ROS). Further, the rate of PAA photolysis, which resulted in the formation of reactive radicals, increased with pH, as evidenced by the observed increase in the molar absorption coefficient of PAA (εPAA). Electron paramagnetic resonance (EPR) tests also indicated that the generation of ROS was significantly enhanced when the pH increased from 5 to 7, and at pH 9, a large amount of •OH were possibly consumed by PAA to form organic radicals, leading to a decrease in the •OH signal. Furthermore, it was observed that •OH is primarily responsible for NOR degradation in the MPUV/PAA process at pH 5, whereas organic radicals were primarily responsible for the degradation at pH 7 and 9. The identification of the transformation products (TPs) led to the observation of different NOR transformation pathways owing to the MPUV/PAA process under different pH conditions. Overall, this study provides a comprehensive understanding of the role of pH on the MPUV/PAA degradation behavior of FQs.

Implication on selection and replacement of granular activated carbon used in biologically activated carbon filters through meta-omics analysis.

Biologically activated carbon (BAC) filters are widely used in China and worldwide as an essential part of advanced water treatment. However, it is unclear how to properly select the granular activated carbon (GAC) used in BAC filters and to determine when GAC should be replaced. In this study, five BAC filters, each filled with a different coconut- or coal-based GAC with different physicochemical properties, were run continuously for 400 days. The structure and function of the microbial community and the quantity of specific enzymes in the BAC filters were investigated through an integrated metagenomic/metaproteomic analysis. The results indicated that GAC adsorption still played a major role in removing organic matter once the filters reached a steady-state, which was attributed to bioregeneration, and the contribution of adsorption might be relatively greater than that of biodegradation. GAC with strong adsorption capacity and high bioregeneration potential selected bacterial communities more phylogenetically closely-related than others. The iodine value could be used as an indicator of BAC performance in terms of organic matter removal in the initial stage of the filters, which is dominated by adsorption. However, it could not be used to assess performance at a later stage when adsorption and biodegradation occurred simultaneously. Pore-size distribution characteristics could be chosen as a potential better indicator compared with the current adsorption indicators, dually representing the adsorption performance and the microbial activity, and the proportion of important pore-size of GAC that is more suitable for BAC filter is suggested. GAC with strongly polar terminal groups is more conducive to the removal of ammonium-nitrogen.

Microbial composition and diversity of drinking water: A full scale spatial-temporal investigation of a city in northern China.

The microbiological water quality of drinking water distribution systems (DWDSs) is of primary importance for public health. The detachment of biofilm attached on the pipe wall attribution to water source switch and the occurrence of potentially pathogenic chlorine-resistant bacteria (CRB) under chlorine disinfection get lots of attention. Studies examining microbial communities after the water source switch, particularly in low-salinity water, have been scant. The UV­chlorine combined disinfection applied in one of the investigated drinking water plants provided insight into the control of CRBs. We applied high-throughput sequencing of the 16S rRNA gene to characterize the bacterial communities of the DWDS in northern China over 1 year. A network comprising four different DWDSs was sampled at 48 sites every season (temperate continental monsoon climate), and the impact of key spatial-temporal and physicochemical parameters was investigated. Overall, the entire bacterial community was not significantly different among the four DWDSs (spatial parameter) but varied with seasons (temporal parameter). The switch in water sources might increase the relative abundance of potentially opportunistic pathogens in DWDSs. UV­chlorine combined disinfection can decrease community diversity and is likely to control the growth of potential opportunistic pathogens in DWDSs.

Peracetic acid-based advanced oxidation processes for decontamination and disinfection of water: A review.

Peracetic acid (PAA) has attracted growing attention as an alternative oxidant and disinfectant in wastewater treatment due to the increased demand to reduce chlorine usage and control disinfection byproducts (DBPs). These applications have stimulated new investigations on PAA-based advanced oxidation processes (AOPs), which can enhance water disinfection and remove micropollutants. The purpose of this review is to conduct a comprehensive analysis of scientific information and experimental data reported in recent years on the applications of PAA-based AOPs for the removal of chemical and microbiological micropollutants from water and wastewater. Various methods of PAA activation, including the supply of external energy and metal/metal-free catalysts, as well as their activation mechanisms are discussed. Then, a review on the usage of PAA-based AOPs for contaminant degradation is given. The degradation mechanisms of organic compounds and the influence of the controlling parameters of PAA-based treatment systems are summarized and discussed. Concurrently, the application of PAA-based AOPs for water disinfection and the related mechanisms of microorganism inactivation are also reviewed. Since combining UV light with PAA is the most commonly investigated PAA-based AOP for simultaneous pathogen inactivation and micropollutant oxidation, we have also focused on PAA microbial inactivation kinetics, together with the effects of key experimental parameters on the process. Moreover, we have discussed the advantages and disadvantages of UV/PAA as an AOP against the well-known and established UV/H2O2. Finally, the knowledge gaps, challenges, and new opportunities for research in this field are discussed. This critical review will facilitate an in-depth understanding of the PAA-based AOPs for water and wastewater treatment and provide useful perspectives for future research and development for PAA-based technologies.

Ceramic nanocomposite membranes and membrane fouling: A review.

Membrane technologies have broad applications in the removal of contaminants from drinking water and wastewater. In recent decades, ceramic membrane has made rapid progress in industrial/municipal wastewater treatment and drinking water treatment owing to their advantageous properties over conventional polymeric membrane. The beneficial characteristics of ceramic membranes include fouling resistance, high permeability, good recoverability, chemical stability, and long life time, which have found applications with the recent innovations in both fabrication methods and nanotechnology. Therefore, ceramic membranes hold great promise for potential applications in water treatment. This paper mainly reviews the progress in the research and development of ceramic membranes, with key focus on porous ceramic membranes and nanomaterial-functionalized ceramic membranes for nanofiltration or catalysis. The current state of the available ceramic membranes in industry and academia, and their potential advantages, limitations and applications are reviewed. The last section of the review focuses on ceramic membrane fouling and the efforts towards ceramic membrane fouling mitigation. The advances in ceramic membrane technologies have rarely been widely reviewed before, therefore, this review could be served as a guide for the new entrants to the field, as well to the established researchers.

An ultrasensitive hybridization chain reaction-amplified CRISPR-Cas12a aptasensor for extracellular vesicle surface protein quantification.

Tumor-derived extracellular vesicle (TEV) protein biomarkers facilitate cancer diagnosis and prognostic evaluations. However, the lack of reliable and convenient quantitative methods for evaluating TEV proteins prevents their clinical application. Methods: Here, based on dual amplification of hybridization chain reaction (HCR) and CRISPR-Cas12a, we developed the apta-HCR-CRISPR assay for direct high-sensitivity detection of TEV proteins. The TEV protein-targeted aptamer was amplified by HCR to produce a long-repeated sequence comprising multiple CRISPR RNA (crRNA) targetable barcodes, and the signals were further amplified by CRISPR-Cas12a collateral cleavage activities, resulting in a fluorescence signal. Results: The established strategy was verified by detecting the TEV protein markers nucleolin and programmed death ligand 1 (PD-L1). Both achieved limit of detection (LOD) values as low as 102 particles/µL, which is at least 104-fold more sensitive than aptamer-ELISA and 102-fold more sensitive than apta-HCR-ELISA. We directly applied our assay to a clinical analysis of circulating TEVs from 50 µL of serum, revealing potential applications of nucleolin+ TEVs for nasopharyngeal carcinoma cancer (NPC) diagnosis and PD-L1+ TEVs for therapeutic monitoring. Conclusion: The platform was simple and easy to operate, and this approach should be useful for the highly sensitive and versatile quantification of TEV proteins in clinical samples.

Insight into PPCP degradation by UV/NH2Cl and comparison with UV/NaClO: Kinetics, reaction mechanism, and DBP formation.

The UV/NH2Cl process is an emerging advanced oxidation process (AOP) that is greatly effective in degrading pharmaceuticals and personal care products (PPCPs). However, detailed information regarding the process is lacking. The degradation of ibuprofen (IBP, an electron-withdrawing PPCP) and naproxen (NPX, an electron-donating PPCP) in UV/NH2Cl and UV/NaClO processes was performed to investigate the applicability and security of the UV/NH2Cl process and compare with those of UV/NaClO. UV/NH2Cl was effective in degrading both IBP and NPX and the degradation followed pseudo-first order kinetics (kIBP = 0.0037 cm2/mJ and kNPX = 0.0044 cm2/mJ). This indicated the broad applicability of UV/NH2Cl to different kinds of PPCPs. Ranges of values of UV intensity (0.3-1.0 mW/cm2) and pH (6.0-8.0) showed little effect on the degradation of PPCPs by UV/NH2Cl based on UV Dose but HCO3- (2-8 mM), natural organic matter (NOM, 2-8 mg/L), and the natural water matrixes were inhibitory. Increasing the dosage of NH2Cl from 0.15 mM to 0.75 mM, resulted in an even increase of kIBP; however, kNPX increased slowly after 0.3 mM NH2Cl. Mechanism experiments involving nitrobenzene showed that •OH was the major radical involved in degrading IBP and NPX via UV/NH2Cl. The electron spin resonance spectroscopy and kinetic modeling results also indicated the larger amount of •OH and weaker reactive chlorine species (mainly ClO• and ClO2•) in UV/NH2Cl compared with UV/NaClO. Compared to UV/NaClO in synthetic and natural water, UV/NH2Cl was a more stable degrader with little pH- and substrate-dependence, while UV/NaClO preferred degrading the electron-donating PPCP and at low pH. The UV/NH2Cl produced less halogenated disinfection byproducts (DBPs) (even nitrogenous DBPs) and was less cytotoxic theoretically than UV/NaClO based on the DBPs included in this study. Thus UV/NH2Cl process may be an effective AOP for water treatment.

Effect of granular activated carbon pore-size distribution on biological activated carbon filter performance.

Proper granular activated carbon (GAC) selection could improve the performance of biological activated carbon (BAC) filters through a combination of adsorption and biodegradation, while the GACs used in BAC filters are now mainly selected according to adsorption function, ignoring biodegradation. In this study, sand filter effluent obtained from a drinking water treatment plant was fed into continuous-flow bench-scale BAC columns operated in parallel over 245 days to examine the effects of GAC pore-size distribution on BAC filter performance, in terms of the dissolved organic carbon (DOC) and disinfection byproduct (DBP) precursors. A metagenomic analysis indicated that bacterial community structure played an important role in BAC filter performance. A significant correlation was found between metabolism-related proteins and the volume of micro-level macropores based on metaproteomic analysis. It is suggested that the adsorption saturation was dynamic and that adsorption played a role in the performance of the BAC filters throughout the 245-day operating period. Renewed adsorption capacity, or bioregeneration, was driven by bacterial metabolic activity. Such activity largely depended on the organic matter adsorbed by the GAC, in which micro-level macropores, especially those with diameters of 0.2-10 µm, played an important but previously unrecognized role. The results suggest that more attention should be paid to well-developed pores and pore-size distribution in the production and selection of GAC used for full-scale drinking water biofilters.

Bioremoval of non-steroidal anti-inflammatory drugs by Pseudoxanthomonas sp. DIN-3 isolated from biological activated carbon process.

The presence of non-steroidal anti-inflammatory drugs (NSAIDs) in the environment is an emerging concern owing to their potential threat on aquatic ecosystems and living organisms. To investigate the bioremoval potential of a biological activated carbon (BAC) filter for the removal of NSAIDs, removal of diclofenac (DCF), ibuprofen (IBU), and naproxen (NAP) by biofilms on a bench-scaled BAC column operated for 400 days was studied. The results showed that the BAC column effectively removed the three NSAIDs (>90%). One bacterial strain isolated from the BAC, Pseudoxanthomonas sp. DIN-3, was able to simultaneously remove DCF, IBU, and NAP, which were supplied as the sole carbon source. In 14 days, 23%, 41%, and 39% of DCF, IBU, and NAP (50 µg L-1) were bioremoved, respectively, and strain DIN-3 eliminated IBU more rapidly than the other two NSAIDs. If only a single drug was added as the sole carbon source, ignoring the other drugs, the removal ability was overestimated by 5.0-27.0%. More efficient bioremoval was achieved, concomitantly with bacterial growth, via a co-metabolism with acetate, glucose, or methanol. Their intermediates were identified by UPLC-QQQ-MS, and their respective degradation pathways were also proposed. Moreover, based on the complete genome sequence of strain DIN-3, 49 related genes encoding the main enzymes involved in DCF, IBU, and NAP biodegradation were identified, including hemE, lpd, yihx, ligC, pobA, and ligA. These results suggested that Pseudoxanthomonas sp. DIN-3 is a potential degrader of DCF, IBU, and NAP, and to the best of our knowledge, this is the first report that demonstrates the bioremoval of DCF, IBU, and NAP simultaneously by an individual bacterial strain isolated from the environment. However, the bioremoval potential should be evaluated when assessing the applicability of the strain in the environment because of the combined effects of various pharmaceutical contaminants. The obtained results provide a foundation for the use of Pseudoxanthomonas sp. DIN-3 in the bioremoval of polycyclic NSAID-contaminated environments.

Seasonal variation characteristic of inhalable microbial communities in PM2.5 in Beijing city, China.

Bacteria and fungi are primary constituents of airborne microbes in fine particulate matter (PM2.5) and significantly impact human health. However, hitherto, seasonal variation and effect of air pollution on microbial community composition and structure are poorly understood. This study analyzed the bacterial and fungal composition of PM2.5 under different air pollution levels during different seasons in Beijing. We altogether collected 75PM2.5 samples during four seasons from April 2014 to January 2015, under different air pollution levels and employed high-throughput sequencing methods to analyze microbial composition. The results showed that air pollution decreased species richness and community diversity of bacteria in PM2.5. The variation in bacterial and fungal community composition and structure was significantly related to the season but there was no correlation between their abundance and pollution levels. Pathogenic bacteria and fungi were more abundant in winter than other seasons. To best of our knowledge, this is the first study that demonstrates seasonal variation characteristics of bacteria and fungi in PM2.5 in heavy haze contaminated areas and highlights the effects of air pollution on the atmospheric microbial community. This study would be useful to other bioaerosol studies focusing on the role of the atmospheric particulate matter on human health.

Mechanisms and toxicity evaluation of the degradation of sulfamethoxazole by MPUV/PMS process.

In this work, a sulfate radical (SO4-)-based advanced oxidation process was applied to the degradation of sulfamethoxazole (SMX). In these experiments, a medium pressure UV (MPUV) lamp was employed to active peroxymonosulfate (PMS). It was found that 98% of SMX was removed by MPUV/PMS at a UV dose of 200 mJ cm-2 (3.95 µM SMX, 0.2 mM PMS, pH0 = 3.7). Direct MPUV photolysis played a remarkable role in SMX removal by MPUV/PMS process. As for the indirect photolysis, SO4- was the major reactive species under acidic and neutral conditions in MPUV/PMS system, while the hydroxyl radical (OH) became the predominant radical under alkaline conditions. The transformation products (TPs) of SMX that formed in the MPUV-only and MPUV/PMS experiments were identified, and the possible degradation pathways were proposed. Photoisomerization of the isoxazole ring was the major pathway of SMX during MPUV-only process. Hydroxylation/oxidation of the aniline and isoxazole ring was the predominant degradation mechanism of SMX by MPUV/PMS. Toxicity evaluation showed that MPUV/PMS was effective at reducing the antibacterial activity of SMX solutions, while MPUV-only was not. However, some TPs with equivalent or even higher antibacterial activity than SMX were formed during the initial degradation period in MPUV/PMS system. Ecotoxicity of SMX and its TPs was also hypothetically predicted via the ECOSAR program, and the results indicated that some TPs could be more toxic than SMX.