Water-dispersible nano-pollutions reshape microbial metabolism in type-specific manners: A metabolic and bacteriological investigation in Escherichia coli

• Water-dispersible nano-pollutions exhibit type-specific toxic effects on E. coli. • Global metabolite profiling was used to characterize metabolic disruption patterns. • Key dysregulated metabolites responsive to nano-pollution exposures were found. • Amino acid metabolism and purine metabolism are perturbed at nano-pollutions. Incomplete separation and recycling of nanoparticles are causing undesirable nanopollution and thus raising great concerns with regard to nanosafety. Since microorganisms are important regulator of physiological processes in many organisms, the interaction between nanopollution and microbial metabolomics and the resultant impact on the host’s health are important but unclear. To investigate how typical nanopollution perturbs microbial growth and metabolism, Escherichia coli (E. coli) in vitro was treated with six water-dispersible nanomaterials (nanoplastic, nanosilver, nano-TiO₂, nano-ZnO, semiconductor quantum dots (QDs), carbon dots (CDs)) at human-/environment-relevant concentration levels. The nanomaterials exhibited type-specific toxic effects on E. coli growth. Global metabolite profiling was used to characterize metabolic disruption patterns in the model microorganism exposed to different nanopollutants. The percentage of significant metabolites (p<0.05, VIP>1) accounted for 6%–38% of the total 293 identified metabolites in each of the nanomaterial-contaminated bacterial groups. Metabolic results also exhibited significant differences between different nanopollutants and dose levels, revealing type-specific and untypical concentration-dependent metabolic responses. Key metabolites responsive to nanopollution exposures were mainly involved in amino acid and purine metabolisms, where 5, 4, and 7 significant metabolic features were included in arginine and proline metabolism, phenylalanine metabolism, and purine metabolism, respectively. In conclusion, this study horizontally compared and demonstrated how typical nanopollution perturbs microbial growth and metabolomics in a type-specific manner, which broadens our understanding of the ecotoxicity of nanopollutants on microorganisms.     

Preparation of reverse osmosis membrane with high permselectivity and anti-biofouling properties for desalination

• Nanoparticle incorporation and anti-biofouling grafting were integrated. • Flux of modified membranes was enhanced without rejection sacrificing. • Anti-biofouling property of modified membranes was improved. High performance is essential for the polyamide (PA) reverse osmosis (RO) membranes during the desalination process. Herein, RO membranes with high permselectivity and anti-biofouling properties were fabricated by nanoparticles incorporation and anti-biofouling grafting. Hydrotalcite (HT) incorporation was performed with a dual role, enhancing water flux and acting as grafting sites. The HT incorporation increased the water flux without sacrificing the salt rejection, compensating for the loss caused by the following grafting reaction. The exposed surface of HT acted as grafting sites for anti-biofouling agent dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOTPAC). The combination of HT incorporation and DMOTPAC grafting endowed RO membranes with high permselectivity and anti-biofouling properties. The water flux of the modified membrane PA-HT-0.06 was 49.8 L/m²·h, which was 16.4% higher than that of the pristine membrane. The salt rejection of PA-HT-0.06 was 99.1%, which was comparable to that of the pristine membrane. As to the fouling of negatively charged lysozyme, the modified membrane’s water flux recovery was superior to that of the pristine membrane (e.g. 86.8% of PA-HT-0.06 compared to 78.2% of PA-pristine). The sterilization rates of PA-HT-0.06 for E. coli and B. subtilis were 97.3% and 98.7%, much higher than those of the pristine membrane (24.0% for E. coli and 26.7% for B. subtilis).     

Comparative genotoxicity of water processed by three drinking water treatment plants with different water treatment procedures

• Genotoxicity of substances is unknown in the water after treatment processes. • Genotoxicity decreased by activated carbon treatment but increased by chlorination. • Halogenated hydrocarbons and aromatic compounds contribute to genotoxicity. • Genotoxicity was assessed by umu test; acute and chronic toxicity by ECOSAR. • Inconsistent results confirmed that genotoxicity cannot be assessed by ECOSAR. Advanced water treatment is commonly used to remove micropollutants such as pesticides, endocrine disrupting chemicals, and disinfection byproducts in modern drinking water treatment plants. However, little attention has been paid to the changes in the genotoxicity of substances remaining in the water following the different water treatment processes. In this study, samples were collected from three drinking water treatment plants with different treatment processes. The treated water from each process was analyzed and compared for genotoxicity and the formation of organic compounds. The genotoxicity was evaluated by an umu test, and the acute and chronic toxicity was analyzed through Ecological Structure- Activity Relationship (ECOSAR). The results of the umu test indicated that biological activated carbon reduced the genotoxicity by 38%, 77%, and 46% in the three drinking water treatment plants, respectively, while chlorination increased the genotoxicity. Gas chromatograph-mass spectrometry analysis revealed that halogenated hydrocarbons and aromatic compounds were major contributors to genotoxicity. The results of ECOSAR were not consistent with those of the umu test. Therefore, we conclude that genotoxicity cannot be determined using ECOSAR .     

Influences and mechanisms of nanofullerene on the horizontal transfer of plasmid-encoded antibiotic resistance genes between E. coli strains

• Sub-inhibitory levels of nC₆₀ promote conjugative transfer of ARGs. • nC₆₀ can induce ROS generation, oxidative stress and SOS response. • nC₆₀ can increase cell membrane permeability and alter gene expression. • Results provide evidence of nC₆₀ promoting antibiotic resistance dissemination. The spread and development of antibiotic resistance globally have led to severe public health problems. It has been shown that some non-antibiotic substances can also promote the diffusion and spread of antibiotic resistance genes (ARGs). Nanofullerene (nC₆₀) is a type of nanomaterial widely used around the world, and some studies have discovered both the biological toxicity and environmental toxicity of nC₆₀. In this study, cellular and molecular biology techniques were employed to investigate the influences of nC₆₀ at sub-minimum inhibitory concentrations (sub-MICs) on the conjugation of ARGs between the E. coli strains. Compared with the control group, nC₆₀ significantly increased the conjugation rates of ARGs by 1.32‒10.82 folds within the concentration range of 7.03‒1800 mg/L. This study further explored the mechanism of this phenomenon, finding that sub-MICs of nC₆₀ could induce the production of reactive oxygen species (ROS), trigger SOS-response and oxidative stress, affect the expression of outer membrane proteins (OMPs) genes, increase membrane permeability, and thus promote the occurrence of conjugation. This research enriches our understanding of the environmental toxicity of nC₆₀, raises our risk awareness toward nC₆₀, and may promote the more rational employment of nC₆₀ materials.     

Removal,distribution and plant uptake of perfluorooctane sulfonate (PFOS) in a simulated constructed wetland system

• PFOS was removed by soil adsorption and plant uptake in the VFCW. • Uptake of PFOS by E. crassipes was more than that of C. alternifolius. • PFOS in wastewater can inhibit the removal of nutrients. • Dosing with PFOS changed the soil microbial community in the VFCW. A vertical-flow constructed wetland (VFCW) was used to treat simulated domestic sewage containing perfluorooctane sulfonate (PFOS). The removal rate of PFOS in the domestic sewage was 93%–98%, through soil adsorption and plant uptake, suggesting that VFCWs can remove PFOS efficiently from wastewater. The removal of PFOS in the VFCW was dependent on soil adsorption and plant uptake; moreover, the percentage of soil adsorption was 61%–89%, and was higher than that of the plants uptake (5%–31%). The absorption capacity of Eichhornia crassipes (E. crassipes) (1186.71 mg/kg) was higher than that of Cyperus alternifolius (C. alternifolius) (162.77 mg/kg) under 10 mg/L PFOS, and the transfer factor of PFOS in E. crassipes and C. alternifolius was 0.04 and 0.58, respectively, indicating that PFOS is not easily translocated to leaves from roots of wetland plants; moreover, uptake of PFOS by E. crassipes was more than that of C. alternifolius because the biomass of E. crassipes was more than that of C. alternifolius and the roots of E. crassipes can take up PFOS directly from wastewater while C. alternifolius needs to do so via its roots in the soil. The concentration of 10 mg/L PFOS had an obvious inhibitory effect on the removal rate of total nitrogen, total phosphorus, chemical oxygen demand, and ammonia nitrogen in the VFCW, which decreased by 15%, 10%, 10% and 12%, respectively. Dosing with PFOS in the wastewater reduced the bacterial richness but increased the diversity in soil because PFOS stimulated the growth of PFOS-tolerant strains.     

Surface water treatment benefits from the presence of algae: Influence of algae on the coagulation behavior of polytitanium chloride

• Emerging titanium coagulation was high-efficient for algae-laden water treatment. • Polytitanium coagulation was capable for both algae and organic matter removal. • Surface water purification was improved by around 30% due to algae inclusion. • Algae functioned as flocculant aid to assist polytitanium coagulation. • Algae could enhance charge neutralization capability of polytitanium coagulant. Titanium-based coagulation has proved to be effective for algae-laden micro-polluted water purification processes. However, the influence of algae inclusion in surface water treatment by titanium coagulation is barely reported. This study reports the influence of both Microcystis aeruginosa and Microcystis wesenbergii in surface water during polytitanium coagulation. Jar tests were performed to evaluate coagulation performance using both algae-free (controlled) and algae-laden water samples, and floc properties were studied using a laser diffraction particle size analyzer for online monitoring. Results show that polytitanium coagulation can be highly effective in algae separation, removing up to 98% from surface water. Additionally, the presence of algae enhanced organic matter removal by up to 30% compared to controlled water containing only organic matter. Polytitanium coagulation achieved significant removal of fluorescent organic materials and organic matter with a wide range of molecular weight distribution (693–4945 Da) even in the presence of algae species in surface water. The presence of algae cells and/or algal organic matter is likely to function as an additional coagulant or flocculation aid, assisting polytitanium coagulation through adsorption and bridging effects. Although the dominant coagulation mechanisms with polytitanium coagulant were influenced by the coagulant dosage and initial solution pH, algae species in surface water could enhance the charge neutralization capability of the polytitanium coagulant. Algae-rich flocs were also more prone to breakage with strength factors approximately 10% lower than those of algae-free flocs. Loose structure of the flocs will require careful handling of the flocs during coagulation-sedimentation-filtration processes.     

Mechanism of dichloromethane disproportionation over mesoporous TiO2 under low temperature

• Mechanism of DCM disproportionation over mesoporous TiO₂ was studied. • DCM was completely eliminated at 350℃ under 1 vol.% humidity. • Anatase (001) was the key for disproportionation. • A competitive oxidation route co-existed with disproportionation. • Disproportionation was favored at low temperature. Mesoporous TiO₂ was synthesized via nonhydrolytic template-mediated sol-gel route. Catalytic degradation performance upon dichloromethane over as-prepared mesoporous TiO₂, pure anatase and rutile were investigated respectively. Disproportionation took place over as-made mesoporous TiO₂ and pure anatase under the presence of water. The mechanism of disproportionation was studied by in situ FTIR. The interaction between chloromethoxy species and bridge coordinated methylenes was the key step of disproportionation. Formate species and methoxy groups would be formed and further turned into carbon monoxide and methyl chloride. Anatase (001) played an important role for disproportionation in that water could be dissociated into surface hydroxyl groups on such structure. As a result, the consumed hydroxyl groups would be replenished. In addition, there was another competitive oxidation route governed by free hydroxyl radicals. In this route, chloromethoxy groups would be oxidized into formate species by hydroxyl radicals transfering from the surface of TiO₂. The latter route would be more favorable at higher temperature.     

Cultivation of Chlorella sp. HQ in inland saline-alkaline water under different light qualities

• Optimal growth of Chlorella in inland saline-alkaline water was achieved by blue LED. • Lipids of Chlorella sp. HQ were mainly composed of C16:0 and C18:2 under various LEDs. • The BiodieselAnalyzer^© software was used to evaluate the Chlorella biodiesel quality. • Chlorella sp. HQ was a high-quality feedstock for biodiesel production. Inland saline-alkaline water can be used for the low-cost cultivation of microalgae, but whether algal biomass under various light sources has the potential to produce biodiesel remains to be developed. Herein, the influence of different light-emitting diode (LEDs) light colors (blue, red, white, mixed blue-red, and mixed blue-white LED) on the growth performance, lipid accumulation, and fatty acid composition of Chlorella sp. HQ cultivated in inland saline-alkaline water was investigated. The highest algal density was obtained under blue LEDs at the end of cultivation, reaching 1.93±0.03 × 10⁷ cells/mL. White LEDs can improve biomass yield, total lipid yield, and triacylglycerol yield per algal cell. The main fatty acid components of Chlorella from inland saline-alkaline water were palmitic acid and linoleic acid. The BiodieselAnalyzer^© software was used to predict algal biodiesel quality by estimating different quality parameters. The cetane number, kinematic viscosity, and density of Chlorella biodiesel were 51.714–67.69, 3.583–3.845 mm²/s, and 0.834–0.863 g/cm³, respectively. This further proved that the Chlorella biomass obtained from inland saline-alkaline water has the potential to be used as a high-quality biodiesel feedstock.     

Transmembrane transport of polycyclic aromatic hydrocarbons by bacteria and functional regulation of membrane proteins

• Explaintheadsorption, uptake and transmembrane transport of PAHs by bacteria. • Analyze functional regulation of membrane proteins inthe transmembrane transport. • Proteomics technology such as iTRAQ labeling was used to access expressed proteins. • Single cell analysis technology wereused to study the morphological structure. In recent years, increasing research has been conducted on transmembrane transport processes and the mechanisms behind the microbial breakdown of polycyclic aromatic hydrocarbons (PAHs), including the role of membrane proteins in transmembrane transport and the mode of transmission. This article explains the adsorption, uptake and transmembrane transport of PAHs by bacteria, the regulation of membrane protein function during the transmembrane transport. There are three different regulation mechanisms for uptake, depending on the state and size of the oil droplets relative to the size of the microbial cells, which are (i) direct adhesion, (ii) emulsification and pseudosolubilization, and (iii) interfacial uptake. Furthermore, two main transmembrane transport modes are introduced, which are (i) active transport and (ii) passive uptake and active efflux mechanism. Meanwhile, introduce the proteomics and single cell analysis technology used to address these areas of research, such as Isobaric tags for relative and absolute quantitation (iTRAQ) technology and Nano Secondary ion mass spectrometry (Nano-SIMS). Additionally, analyze the changes in morphology and structure and the characteristics of microbial cell membranes in the process of transmembrane transport. Finally, recognize the microscopic mechanism of PAHs biodegradation in terms of cell and membrane proteins are of great theoretical and practical significance for understanding the factors that influence the efficient degradation of PAHs contaminants in soil and for remediating the PAHs contamination in this area with biotechnology.     

PM-support interfacial effect and oxygen mobility in Pt,Pd or Rh-loaded (Ce,Zr,La)O2 catalysts

• Pt/CZL exhibits the optimum catalytic performance for HC and NO_x elimination. • The strong PM-Ce interaction favors the oxygen mobility and DOSC. • Pd/CZL shows higher catalytic activity for CO conversion due to more O_latt species. • Great oxygen mobility at high temperature broadens the dynamic operation window. • The relationship between DOSC and catalytic performance is revealed. The physicochemical properties of Pt-, Pd- and Rh- loaded (Ce,Zr,La)O₂ (shorted for CZL) catalysts before/after aging treatment were systematically characterized by various techniques to illustrate the relationship of the dynamic oxygen storage/release capacity and redox ability with their catalytic performances for HC, NO_x and CO conversions. Pt/CZL catalyst exhibits the optimum catalytic performance for HC and NO_x elimination, which mainly contribute to its excellent redox ability and dynamic oxygen storage/release capacity (DOSC) at lower temperature due to the stronger PM (precious metals)-support interaction. However, the worse stability of Pt-O-Ce species and volatile Pt oxides easily result in the dramatical decline in catalytic activity after aging. Pd/CZL shows higher catalytic activity for CO conversion by reason of more O_latt species as the active oxygen for CO oxidation reaction. Rh/CZL catalyst displays the widest dynamic operation window for NO_x elimination as a result of greater oxygen mobility at high temperature, and the ability to retain more Rh-O-Ce species after calcined at 1100°C effectively restrains sintering of active RhO_x species, improving the thermal stability of Rh/CZL catalyst.     

Bioinspired and biomimetic membranes for water purification and chemical separation: A review

•The history of biological and artificial water channels is reviewed. •A comprehensive channel characterization platform is introduced. •Rationale designs and fabrications of biomimetic membranes are summarized. •The advantages, limitations, and challenges of biomimetic membranes are discussed. •The prospect and scalable solutions of biomimetic membranes are discussed. Bioinspired and biomimetic membranes that contain biological transport channels or attain their structural designs from biological systems have been through a remarkable development over the last two decades. They take advantage of the exceptional transport properties of those channels, thus possess both high permeability and selectivity, and have emerged as a promising solution to existing membranes. Since the discovery of biological water channel proteins aquaporins (AQPs), extensive efforts have been made to utilize them to make separation membranes–AQP-based membranes, which have been commercialized. The exploration of AQPs’ unique structures and transport properties has resulted in the evolution of biomimetic separation materials from protein-based to artificial channel-based membranes. However, large-scale, defect-free biomimetic membranes are not available yet. This paper reviews the state-of-the-art biomimetic membranes and summarizes the latest research progress, platform, and methodology. Then it critically discusses the potential routes of this emerging area toward scalable applications. We conclude that an appropriate combination of bioinspired concepts and molecular engineering with mature polymer industry may lead to scalable polymeric membranes with intrinsic selective channels, which will gain the merit of both desired selectivity and scalability.     

Metagenomic analysis on resistance genes in water and microplastics from a mariculture system

• Total 174 subtypes of ARGs were detected by metagenomic analysis. • Chloramphenicol resistance genes were the dominant ARGs in water and microplastics. • The abundances of MRGs were much higher than those of ARGs. • Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant phylum. • Microplastics in mariculture system could enrich most of MRGs and some ARGs. Microplastics existing widely in different matrices have been regarded as a reservoir for emerging contaminants. Mariculture systems have been observed to host microplastics and antibiotic resistance genes (ARGs). However, more information on proliferation of ARGs and metal resistance genes (MRGs) in mariculture system at the presence of microplastics is needed. This study used metagenomic analysis to investigate the distribution of ARGs and MRGs in water and microplastics of a typical mariculture pond. Total 18 types including 174 subtypes of ARGs were detected with the total relative abundances of 1.22/1.25 copies per 16S rRNA copy for microplastics/water. Chloramphenicol resistance genes were the dominant ARGs with the abundance of 0.35/0.42 copies per 16S rRNA copy for microplastics/water. Intergron intI1 was dominant gene among 6 detected mobile genetic elements (MGEs) with the abundance of 75.46/68.70 copies per 16S rRNA copy for water/microplastics. Total 9 types including 46 subtypes of MRGs were detected with total abundance of 5.02 × 10²/6.39 × 10² copies per 16S rRNA copy for water/ microplastics while genes resistant to copper and iron served as the dominant MRGs. Proteobacteria, Bacteroidetes, and Actinobacteria accounted for 84.2%/89.5% of total microbial community. ARGs with relatively high abundance were significantly positively related to major genera, MGEs, and MRGs. Microplastics in mariculture system could enrich most of MRGs and some ARGs to serve as potential reservoir for these pollutants. The findings of this study will provide important information on resistance gene pollution at presence of microplastics in the mariculture system for further proposing suitable strategy of environmental management.     

Ceramic water filter for point-of-use water treatment in developing countries: Principles,challenges and opportunities

• CWF is a sustainable POU water treatment method for developing areas. • CWF manufacturing process is critical for its filtration performance. • Simultaneous increase of flow rate and pathogen removal is a challenge. • Control of pore size distribution holds promises to improve CWF efficiency. • Novel coatings of CWFs are a promising method to improve contaminant removal. Drinking water source contamination poses a great threat to human health in developing countries. Point-of-use (POU) water treatment techniques, which improve drinking water quality at the household level, offer an affordable and convenient way to obtain safe drinking water and thus can reduce the outbreaks of waterborne diseases. Ceramic water filters (CWFs), fabricated from locally sourced materials and manufactured by local labor, are one of the most socially acceptable POU water treatment technologies because of their effectiveness, low-cost and ease of use. This review concisely summarizes the critical factors that influence the performance of CWFs, including (1) CWF manufacturing process (raw material selection, firing process, silver impregnation), and (2) source water quality. Then, an in-depth discussion is presented with emphasis on key research efforts to address two major challenges of conventional CWFs, including (1) simultaneous increase of filter flow rate and bacterial removal efficiency, and (2) removal of various concerning pollutants, such as viruses and metal(loid)s. To promote the application of CWFs, future research directions can focus on: (1) investigation of pore size distribution and pore structure to achieve higher flow rates and effective pathogen removal by elucidating pathogen transport in porous ceramic and adjusting manufacture parameters; and (2) exploration of new surface modification approaches with enhanced interaction between a variety of contaminants and ceramic surfaces.     

Assessment of antibiotic resistance genes in dialysis water treatment processes

• Quantitative global ARGs profile in dialysis water was investigated. • Totally 35 ARGs were found in the dialysis treatment train. • 29 ARGs (highest) were found in carbon filtration effluent. • erm and mtrD-02 occurred in the final effluent. • The effluent was associated with health risks even after RO treatment. Dialysis water is directly related to the safety of hemodialysis patients, thus its quality is generally ensured by a stepwise water purification cascade. To study the effect of water treatment on the presence of antibiotic resistance genes (ARGs) in dialysis water, this study used propidium monoazide (PMA) in conjunction with high throughput quantitative PCR to analyze the diversity and abundance of ARGs found in viable bacteria from water having undergone various water treatment processes. The results indicated the presence of 35 ARGs in the effluents from the different water treatment steps. Twenty-nine ARGs were found in viable bacteria from the effluent following carbon filtration, the highest among all of the treatment processes, and at 6.96 Log (copies/L) the absolute abundance of the cphA gene was the highest. Two resistance genes, erm (36) and mtrD-02, which belong to the resistance categories macrolides-lincosamides-streptogramin B (MLSB) and other/efflux pump, respectively, were detected in the effluent following reverse osmosis treatment. Both of these genes have demonstrated the potential for horizontal gene transfer. These results indicated that the treated effluent from reverse osmosis, the final treatment step in dialysis-water production, was associated with potential health risks.     

Locally enhanced electric field treatment (LEEFT) for water disinfection

• Nanowire-assisted LEEFT is applied for water disinfection with low voltages. • LEEFT inactivates bacteria by disrupting cell membrane through electroporation. • Multiple electrodes and device configurations have been developed for LEEFT. • The LEEFT is low-cost, highly efficient, and produces no DBPs. • The LEEFT can potentially be applicable for water disinfection at all scales. Water disinfection is a critical step in water and wastewater treatment. The most widely used chlorination suffers from the formation of carcinogenic disinfection by-products (DBPs) while alternative methods (e.g., UV, O₃, and membrane filtration) are limited by microbial regrowth, no residual disinfectant, and high operation cost. Here, a nanowire-enabled disinfection method, locally enhanced electric field treatment (LEEFT), is introduced with advantages of no chemical addition, no DBP formation, low energy consumption, and efficient microbial inactivation. Attributed to the lightning rod effect, the electric field near the tip area of the nanowires on the electrode is significantly enhanced to inactivate microbes, even though a small external voltage (usually<5 V) is applied. In this review, after emphasizing the significance of water disinfection, the theory of the LEEFT is explained. Subsequently, the recent development of the LEEFT technology on electrode materials and device configurations are summarized. The disinfection performance is analyzed, with respect to the operating parameters, universality against different microorganisms, electrode durability, and energy consumption. The studies on the inactivation mechanisms during the LEEFT are also reviewed. Lastly, the challenges and future research of LEEFT disinfection are discussed.     

Hexavalent chromium in drinking water: Chemistry,challenges and future outlook on Sn(II)- and photocatalyst-based treatment

• Wide occurrence of Cr(VI) in US source drinking water. • A strong dependence of occurrence on groundwater sources. • Elucidate Redox and equilibrium chemistry of Cr(VI). • Sn(II)-based and TiO₂-based reductive treatments hold extreme promise. • Key challenges include residual waste, Cr(VI) re-generation and socioeconomic drivers. Chromium (Cr) typically exists in either trivalent and hexavalent oxidation states in drinking water, i.e., Cr(III) and Cr(VI), with Cr(VI) of particular concern in recent years due to its high toxicity and new regulatory standards. This Account presented a critical analysis of the sources and occurrence of Cr(VI) in drinking water in the United States, analyzed the equilibrium chemistry of Cr(VI) species, summarized important redox reaction relevant to the fate of Cr(VI) in drinking water, and critically reviewed emerging Cr(VI) treatment technologies. There is a wide occurrence of Cr(VI) in US source drinking water, with a strong dependence on groundwater sources, mainly due to naturally weathering of chromium-containing aquifers. Challenges regarding traditional Cr(VI) treatment include chemical cost, generation of secondary waste and inadvertent re-generation of Cr(VI) after treatment. To overcome these challenges, reductive Cr(VI) treatment technologies based on the application of stannous tin or electron-releasing titanium dioxide photocatalyst hold extreme promise in the future. To moving forward in the right direction, three key questions need further exploration for the technology implementation, including effective management of residual waste, minimizing the risks of Cr(VI) re-occurrence downstream of drinking water treatment plant, and promote the socioeconomic drivers for Cr(VI) control in the future.     

Review on remediation technologies for arsenic-contaminated soil

• Recent progress of As-contaminated soil remediation technologies is presented. • Phytoextraction and chemical immobilization are the most widely used methods. • Novel remediation technologies for As-contaminated soil are still urgently needed. • Methods for evaluating soil remediation efficiency are lacking. • Future research directions for As-contaminated soil remediation are proposed. Arsenic (As) is a top human carcinogen widely distributed in the environment. As-contaminated soil exists worldwide and poses a threat on human health through water/food consumption, inhalation, or skin contact. More than 200 million people are exposed to excessive As concentration through direct or indirect exposure to contaminated soil. Therefore, affordable and efficient technologies that control risks caused by excess As in soil must be developed. The presently available methods can be classified as chemical, physical, and biological. Combined utilization of multiple technologies is also common to improve remediation efficiency. This review presents the research progress on different remediation technologies for As-contaminated soil. For chemical methods, common soil washing or immobilization agents were summarized. Physical technologies were mainly discussed from the field scale. Phytoextraction, the most widely used technology for As-contaminated soil in China, was the main focus for bioremediation. Method development for evaluating soil remediation efficiency was also summarized. Further research directions were proposed based on literature analysis.     

Surface modification of mesoporous silica nanoparticle with 4-triethoxysilylaniline to enhance seawater desalination properties of thin-film nanocomposite reverse osmosis membranes

• Mesoporous silica nanoparticle was modified with 4-triethoxysilylaniline. • AMSN-based TFN-RO membranes were prepared for seawater desalination. • Water transport capability of the AMSN was limited by polyamide. • Polyamide still plays a key role in permeability of the TFN RO membranes. Mesoporous silica nanoparticles (MSN), with higher water permeability than NaA zeolite, were used to fabricate thin-film nanocomposite (TFN) reverse osmosis (RO) membranes. However, only aminoalkyl-modified MSN and low-pressure (less than 2.1 MPa) RO membrane were investigated. In this study, aminophenyl-modified MSN (AMSN) were synthesized and used to fabricate high-pressure (5.52 MPa) RO membranes. With the increasing of AMSN dosage, the crosslinking degree of the aromatic polyamide decreased, while the hydrophilicity of the membranes increased. The membrane morphology was maintained to show a ridge-and-valley structure, with only a slight increase in membrane surface roughness. At the optimum conditions (AMSN dosage of 0.25 g/L), when compared with the pure polyamide RO membrane, the water flux of the TFN RO membrane (55.67 L/m²/h) was increased by about 21.6%, while NaCl rejection (98.97%) was slightly decreased by only 0.29%. However, the water flux of the membranes was much lower than expected. We considered that the enhancement of RO membrane permeability is attributed to the reduction of the effective thickness of the PA layer.     

Algae (Raphidocelis subcapitata) mitigate combined toxicity of microplastic and lead on Ceriodaphnia dubia

• Micro-plastics (MPs) significantly increase Pb toxicity. • Algae reduce the combined toxicity of MP and Pb. • The toxicity increase comes from high soluble Pb and MP-Pb uptake. • The toxicity reduction might come from energy related pathway. Microplastics (MPs) have been recognized as a new class of emerging contaminants in recent years. They not only directly impact aquatic organisms, but also indirectly impact these organisms by interacting with background toxins in the environment. Moreover, under realistic environmental conditions, algae, a natural food for aquatic organisms, may alter the toxicity pattern related to MPs. In this research, we first examined the toxicity of MPs alone, and their effect on the toxicity of lead (Pb) on Ceriodaphnia dubia (C. dubia), a model aquatic organism for toxicity survey. Then, we investigated the effect of algae on the combined toxicity of MPs and Pb. We observed that, MPs significantly increased Pb toxicity, which was related to the increase in soluble Pb concentration and the intake of Pb-loaded MPs, both of which increased the accumulation of Pb in C. dubia. The presence of algae mitigated the combined toxicity of MPs and Pb, although algae alone increased Pb accumulation. Therefore, the toxicity mitigation through algae uptake came from mechanisms other than Pb accumulation, which will need further investigation.     

Reutilize tire in microbial fuel cell for enhancing the nitrogen removal of the anammox process coupled with iron-carbon micro-electrolysis

• MFC promoted the nitrogen removal of anammox with Fe-C micro-electrolysis. • Reutilize pyrolysis waste tire as micro-electrolysis and electrode materials. • Total nitrogen removal efficiency of modified MFC increased to 85.00%. • Candidatus kuenenia and SM1A02 were major genera responsible for nitrogen removal. In this study, microbial fuel cells (MFCs) were explored to promote the nitrogen removal performance of combined anaerobic ammonium oxidation (anammox) and Fe-C micro-electrolysis (CAE) systems. The average total nitrogen (TN) removal efficiency of the modified MFC system was 85.00%, while that of the anammox system was 62.16%. Additionally, the effective operation time of this system increased from six (CAE system alone) to over 50 days, significantly promoting TN removal. The enhanced performance could be attributed to the electron transferred from the anode to the cathode, which aided in reducing nitrate/nitrite in denitrification. The H⁺ released through the proton exchange membrane caused a decrease in the pH, facilitating Fe corrosion. The pyrolyzed waste tire used as the cathode could immobilize microorganisms, enhance electron transport, and produce a natural Fe-C micro-electrolysis system. According to the microbial community analysis, Candidatus kuenenia was the major genus involved in the anammox process. Furthermore, the SM1A02 genus exhibited the highest abundance and was enriched the fastest, and could be a novel potential strain that aids the anammox process.