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.     

Fate of microplastics in a coastal wastewater treatment plant: Microfibers could partially break through the integrated membrane system

• Fate of microplastics in integrated membrane system for water reuse was investigated. • Integrated membrane system has high removal efficiency (>98%) for microplastics. • Microplastics (>93%) were mainly removed through membrane bioreactor treatment. • Small scale fiber plastics (<200 μm) could break through reverse osmosis (RO) system. • The flux of microplastics maintained at 2.7 × 10¹¹ MPs/d after the RO treatment. Rare information on the fate of microplastics in the integrated membrane system (IMS) system in full-scale wastewater treatment plant was available. The fate of microplastics in IMS in a coastal reclaimed water plant was investigated. The removal rate of microplastics in the IMS system reached 93.2% after membrane bioreactor (MBR) treatment while that further increased to 98.0% after the reverse osmosis (RO) membrane process. The flux of microplastics in MBR effluent was reduced from 1.5 × 10¹³ MPs/d to 10.2 × 10¹¹ MPs/d while that of the RO treatment decreased to 2.7 × 10¹¹ MPs/d. Small scale fiber plastics (<200 μm) could break through RO system according to the size distribution analysis. The application of the IMS system in the reclaimed water plant could prevent most of the microplastics from being discharged in the coastal water. These findings suggested that the IMS system was more efficient than conventional activated sludge system (CAS) for the removal of microplastics, while the discharge of small scale fiber plastics through the IMS system should also not be neglected because small scale fiber plastics (<200 μm) could break through IMS system equipped with the RO system.     

Research progress on distribution,sources, identification,toxicity, and biodegradation of microplastics in the ocean,freshwater, and soil environment

• Microplastics are widely found in both aquatic and terrestrial environments. • Cleaning products and discarded plastic waste are primary sources of microplastics. • Microplastics have apparent toxic effects on the growth of fish and soil plants. • Multiple strains of biodegradable microplastics have been isolated. Microplastics (MPs) are distributed in the oceans, freshwater, and soil environment and have become major pollutants. MPs are generally referred to as plastic particles less than 5 mm in diameter. They consist of primary microplastics synthesized in microscopic size manufactured production and secondary microplastics generated by physical and environmental degradation. Plastic particles are long-lived pollutants that are highly resistant to environmental degradation. In this review, the distribution and possible sources of MPs in aquatic and terrestrial environments are described. Moreover, the adverse effects of MPs on natural creatures due to ingestion have been discussed. We also have summarized identification methods based on MPs particle size and chemical bond. To control the pollution of MPs, the biodegradation of MPs under the action of different microbes has also been reviewed in this work. This review will contribute to a better understanding of MPs pollution in the environment, as well as their identification, toxicity, and biodegradation in the ocean, freshwater, and soil, and the assessment and control of microplastics exposure.     

The abundance,characteristics and diversity of microplastics in the South China Sea: Observation around three remote islands

• A high abundance of floating MPs was found in the southern South China Sea. • Transparent film and fiber were predominant in water and organisms, respectively. • 84.7% of floating MPs and 54.5% of MPs in vivo belonged to PP and PE. • Characteristics of MP in organisms were different from those of inshore ones. Surrounded by emerging markets with considerable plastic consumption, the South China Sea has been a focus area of microplastic research. A survey on the floating microplastics (>0.3 mm) and microplastics ingested by fish and mollusks was conducted around three remote islands here. Compared with the results from several previous studies, a high abundance of floating microplastics (with a median of 1.9 × 10⁵ items/km² or 0.7 items/m³) was observed, revealing another “hot spot” for microplastics. Polyolefin, especially polypropylene, was the main component. The diversity index and evenness index were calculated and evaluated based on the composition of microplastics. The characteristic peaks of Raman spectra concerning pigmented microplastics were provided. Transparent sheets/films were predominant in the water sample, which was quite different from a similar study in this sea area (8.9% for film), and only 16.4% of floating microplastics (>0.3 mm) were fibers/lines, implying that the main sources of floating microplastics (>0.3 mm) might be household/agricultural consumption activities. The transparent fiber/line was also dominant in organisms. It is suggested that the main sources of microplastics ingested by organisms might be both fabric fibers and fishing/aquaculture.     

Effects of hydraulic retention time on net present value and performance in a membrane bioreactor treating antibiotic production wastewater

• The membrane bioreactor cost decreased by 38.2% by decreasing HRT from 72 h to 36 h. • Capital and operation costs contributed 62.1% and 37.9% to decreased costs. • The membrane bioreactor is 32.6% cheaper than the oxidation ditch for treatment. • The effluent COD also improved from 709.93±62.75 mg/L to 280±17.32 mg/L. • Further treatment also benefited from lower pretreatment investment. A cost sensitivity analysis was performed for an industrial membrane bioreactor to quantify the effects of hydraulic retention times and related operational parameters on cost. Different hydraulic retention times (72–24 h) were subjected to a flat-sheet membrane bioreactor updated from an existing 72 h oxidation ditch treating antibiotic production wastewater. Field experimental data from the membrane bioreactor, both full-scale (500 m³/d) and pilot (1.0 m³/d), were used to calculate the net present value (NPV), incorporating both capital expenditure (CAPEX) and operating expenditure. The results showed that the tank cost was estimated above membrane cost in the membrane bioreactor. The decreased hydraulic retention time from 72 to 36 h reduced the NPV by 38.2%, where capital expenditure contributed 24.2% more than operational expenditure. Tank construction cost was decisive in determining the net present value contributed 62.1% to the capital expenditure. The membrane bioreactor has the advantage of a longer lifespan flat-sheet membrane, while flux decline was tolerable. The antibiotics decreased to 1.87±0.33 mg/L in the MBR effluent. The upgrade to the membrane bioreactor also benefited further treatments by 10.1%–44.7% lower direct investment.     

Sorption mechanisms of diphenylarsinic acid on natural magnetite and siderite: Evidence from sorption kinetics,sequential extraction and extended X-ray absorption fine-structure spectroscopy analysis

• DPAA sorption followed pseudo-secondary and intra-particle diffusion models. • Chemical bonding and intra-particle diffusion were dominant rate-limiting steps. • DPAA simultaneously formed inner- and outer-sphere complexes on siderite. • DPAA predominantly formed occluded inner-sphere complexes on magnetite. • Bidentate binuclear bond was identified for DPAA on siderite and magnetite. Diphenylarsinic acid (DPAA) is both the prime starting material and major metabolite of chemical weapons (CWs). Because of its toxicity and the widespread distribution of abandoned CWs in burial site, DPAA sorption by natural Fe minerals is of considerable interest. Here we report the first study on DPAA sorption by natural magnetite and siderite using macroscopic sorption kinetics, sequential extraction procedure (SEP) and microscopic extended X-ray absorption fine-structure spectroscopy (EXAFS). Our results show that the sorption pseudo-equilibrated in 60 minutes and that close to 50% and 20%–30% removal can be achieved for magnetite and siderite, respectively, at the initial DPAA concentrations of 4–100 mg/L. DPAA sorption followed pseudo-secondary and intra-particle diffusion kinetics models, and the whole process was mainly governed by intra-particle diffusion and chemical bonding. SEP and EXAFS results revealed that DPAA mainly formed inner-sphere complexes on magnetite (>80%), while on siderite it simultaneously resulted in outer-sphere and inner-sphere complexes. EXAFS analysis further confirmed the formation of inner-sphere bidentate binuclear corner-sharing complexes (²C) for DPAA. Comparison of these results with previous studies suggests that phenyl groups are likely to impact the sorption capacity and structure of DPAA by increasing steric hindrance or affecting the way the central arsenic (As) atom maintains charge balance. These results improve our knowledge of DPAA interactions with Fe minerals, which will help to develop remediation technology and predict the fate of DPAA in soil-water environments.     

Electricity-driven ammonia oxidation and acetate production in microbial electrosynthesis systems

• MES was constructed for simultaneous ammonia removal and acetate production. • Energy consumption was different for total nitrogen and ammonia nitrogen removal. • Energy consumption for acetate production was about 0.04 kWh/g. • Nitrate accumulation explained the difference of energy consumption. • Transport of ammonia and acetate across the membrane deteriorated the performance. Microbial electrosynthesis (MES) is an emerging technology for producing chemicals, and coupling MES to anodic waste oxidation can simultaneously increase the competitiveness and allow additional functions to be explored. In this study, MES was used for the simultaneous removal of ammonia from synthetic urine and production of acetate from CO₂. Using graphite anode, 83.2%±5.3% ammonia removal and 28.4%±9.9% total nitrogen removal was achieved, with an energy consumption of 1.32 kWh/g N for total nitrogen removal, 0.45 kWh/g N for ammonia nitrogen removal, and 0.044 kWh/g for acetate production. Using boron-doped diamond (BDD) anode, 70.9%±12.1% ammonia removal and 51.5%±11.8% total nitrogen removal was obtained, with an energy consumption of 0.84 kWh/g N for total nitrogen removal, 0.61 kWh/g N for ammonia nitrogen removal, and 0.043 kWh/g for acetate production. A difference in nitrate accumulation explained the difference of total nitrogen removal efficiencies. Transport of ammonia and acetate across the membrane deteriorated the performance of MES. These results are important for the development of novel electricity-driven technologies for chemical production and pollution removal.     

TiO2@palygorskite composite for the efficient remediation of oil spills via a dispersion-photodegradation synergy

• A novel and multi-functional clay-based oil spill remediation system was constructed. • TiO₂@PAL functions as a particulate dispersant to break oil slick into tiny droplets. • Effective dispersion leads to the direct contact of TiO₂ with oil pollutes directly. • TiO₂ loaded on PAL exhibits efficient photodegradation for oil pollutants. • TiO₂@PAL shows a typical dispersion-photocatalysis synergistic remediation. Removing spilled oil from the water surface is critically important given that oil spill accidents are a common occurrence. In this study, TiO₂@Palygorskite composite prepared by a simple coprecipitation method was used for oil spill remediation via a dispersion-photodegradation synergy. Diesel could be efficiently dispersed into small oil droplets by TiO₂@Palygorskite. These dispersed droplets had an average diameter of 20–30 mm and exhibited good time stability. The tight adsorption of TiO₂@Palygorskite on the surface of the droplets was observed in fluorescence and SEM images. As a particulate dispersant, the direct contact of TiO₂@Palygorskite with oil pollutants effectively enhanced the photodegradation efficiency of TiO₂ for oil. During the photodegradation process, •O₂⁻and •OH were detected by ESR and radical trapping experiments. The photodegradation efficiency of diesel by TiO₂@Palygorskite was enhanced by about 5 times compared with pure TiO₂ under simulated sunlight irradiation. The establishment of this new dispersion-photodegradation synergistic remediation system provides a new direction for the development of marine oil spill remediation.     

Characterization of value-added chemicals derived from the thermal hydrolysis and wet oxidation of sewage sludge

• Hydrothermal treatment can greatly improve resource recovery from sewage sludge. • tCOD removal during WO was ~55% compared with ~23% after TH. • TOC solubilization during hydrothermal treatment followed first-order kinetics. • Solids and carbon balance confirmed loss of organics during thermal hydrolysis. • Reaction pathways for thermal hydrolysis and wet oxidation are proposed. We evaluated the effect of hydrothermal pretreatments, i.e., thermal hydrolysis (TH) and wet oxidation (WO) on sewage sludge to promote resource recovery. The hydrothermal processes were performed under mild temperature conditions (140°C–180°C) in a high pressure reactor. The reaction in acidic environment (pH= 3.3) suppressed the formation of the color imparting undesirable Maillard’s compounds. The oxidative conditions resulted in higher volatile suspended solids (VSS) reduction (~90%) and chemical oxygen demand (COD) removal (~55%) whereas TH caused VSS and COD removals of ~65% and ~27%, respectively at a temperature of 180°C. During TH, the concentrations of carbohydrates and proteins in treated sludge were 400–1000 mg/L and 1500–2500 mg/L, respectively. Whereas, WO resulted in solids solubilization followed by oxidative degradation of organics into smaller molecular weight carboxylic acids such as acetic acid (~400–500 mg/L). Based on sludge transformation products generated during the hydrothermal pretreatments, simplified reaction pathways are predicted. Finally, the application of macromolecules (such as proteins), VFAs and nutrients present in the treated sludge are also discussed. The future study should focus on the development of economic recovery methods for various value-added compounds.     

Removal of arsenic by pilot-scale vertical flow constructed wetland

• VFCWs are effective for the treatment of arsenic-containing wastewater. • Arsenic removal did not affect the removal of nutrients, except for TP in CW500. • Arsenic removal was highest when the temperature peaked and the reed was in bloom. • Substrate accumulation contributed more to arsenic removal than plant absorption. Four pilot-scale Vertical Flow Constructed Wetlands (VFCWs) filled with gravel and planted with Phragmites australis were operated for seven months in the field to study the efficiency of arsenic removal in contaminated wastewater. The average arsenic removal efficiency by the VFCWs was 52.0%±20.2%, 52.9%±21.3%, and 40.3%±19.4% at the theoretical concentrations of 50 μg/L (CW50), 100 μg/L (CW100), and 500 μg/L (CW500) arsenic in the wastewater, respectively. The results also showed no significant differences in the removal efficiency for conventional contaminants (nitrogen, phosphorus, or chemical oxygen demand) between wastewater treatments that did or did not contain arsenic (P>0.05), except for phosphorus in CW500. The highest average monthly removal rate of arsenic occurred in August (55.9%–74.5%) and the lowest in November (7.8%–15.5%). The arsenic removal efficiency of each VFCW was positively correlated with temperature (P<0.05). Arsenic accumulated in both substrates and plants, with greater accumulation associated with increased arsenic concentrations in the influent. The maximum accumulated arsenic concentrations in the substrates and plants at the end of the experiment were 4.47 mg/kg and 281.9 mg/kg, respectively, both present in CW500. The translocation factor (TF) of arsenic in the reeds was less than 1, with most of the arsenic accumulating in the roots. The arsenic mass balance indicated that substrate accumulation contributed most to arsenic removal (19.9%–30.4%), with lower levels in plants (3.8%–9.5%). In summary, VFCWs are effective for the treatment of arsenic-containing wastewater.     

Quantitative analysis of microplastics in coastal tidal-flat reclamation in Dongtai,China

• Reclamation projects are important disturbances on microplastic risk in coasts. • Tidal-flat reclamation area is a large storage medium for sedimentary microplastics. • Aging and distribution features of soil microplastics show spatial heterogeneity. • Coastal weathered engineering geotextiles are a significant threat to marine health. Coastal tidal flats have received considerable attention in recent years, as they provide a direct channel for the discharge of terrestrial microplastics into the ocean. Land reclamation is occurring increasingly frequently in coastal tidal-flats; however, the environmental impacts of these activities remain unclear. Therefore, this pioneering study assessed the microplastic emission characteristics of reclamation geotextiles and performed a risk assessment accordingly. Morphological characterization of geotextile samples collected from five sites in Dongtai, China, provided evidence of sedimentary weathering. Based on several assumptions, the average abundance of microplastics in soil covered by geotextiles was estimated to reach 349±137 particles/kg dry weight, with the total microplastic load in the reclaimed area estimated to be 20.67±8.06 t. Compared with previous studies, this research demonstrates that coastal reclamation areas store a high concentration of microplastics, aggravating marine microplastic pollution. Moreover, conditional fragmentation model results revealed that the weathering and distribution characteristics of soil microplastics in coastal tidal-flat areas exhibit spatial heterogeneity, being more easily affected by natural factors (such as tides) than those in inland areas. As a result of tides, the annual discharge of geotextile-originating microplastics from the studied areas into the ocean was approximately 2465.52±960.77 t. These findings prove that the risks posed by engineering-microplastics are significant, indicating that further investigations are required on the precise laws of transfer and migration, as well as the toxicity mechanisms, in order to improve analytical techniques and policies in this field.     

Sludge fermentation liquid addition attained advanced nitrogen removal in low C/N ratio municipal wastewater through short-cut nitrification-denitrification and partial anammox

• Sludge fermentation liquid addition resulted in a high NAR of 97.4%. • Extra NH₄⁺-N from SFL was removed by anammox in anoxic phase. • Nitrogen removal efficiency of 92.51% was achieved in municipal wastewater. • The novel system could efficiently treat low COD/N municipal wastewater. Biological nitrogen removal of wastewater with low COD/N ratio could be enhanced by the addition of wasted sludge fermentation liquid (SFL), but the performance is usually limited by the introducing ammonium. In this study, the process of using SFL was successfully improved by involving anammox process. Real municipal wastewater with a low C/N ratio of 2.8–3.4 was treated in a sequencing batch reactor (SBR). The SBR was operated under anaerobic-aerobic-anoxic (AOA) mode and excess SFL was added into the anoxic phase. Stable short-cut nitrification was achieved after 46d and then anammox sludge was inoculated. In the stable period, effluent total inorganic nitrogen (TIN) was less than 4.3 mg/L with removal efficiency of 92.3%. Further analysis suggests that anammox bacteria, mainly affiliated with Candidatus_Kuenenia, successfully reduced the external ammonia from the SFL and contributed approximately 28%–43% to TIN removal. Overall, this study suggests anammox could be combined with SFL addition, resulting in a stable enhanced nitrogen biological removal.     

What have we known so far for fluorescence staining and quantification of microplastics: A tutorial review

• Fluorescence staining provides a fast and easy method to quantify microplastics. • Factors that influence staining are summarized to obtain an optimum staining effect. • Natural organic matter can be stained by dye and interfere with quantification. • Fluorescence staining is applied in both field and laboratory studies. • Future work involves developing new dyes and automated image-analysis methods. Understanding the fate and toxicity of microplastics (MPs,<5 mm plastic particles) is limited by quantification methods. This paper summarizes the methods in use and presents new ones. First, sampling and pretreatment processes of MPs, including sample collection, digestion, density separation, and quality control are reviewed. Then the promising and convenient staining procedures and quantification methods for MPs using fluorescence dyes are reviewed. The factors that influence the staining of MPs, including their physicochemical properties, are summarized to provide an optimal operation procedure. In general, the digestion step is crucial to eliminate natural organic matter (NOM) to avoid interference in quantification. Chloroform was reported to be the most appropriate solvent, and 10–20 μg/mL are recommended as optimal dye concentrations. In addition, a heating and cooling procedure is recommended to maintain the fluorescence intensity of MPs for two months. After staining, a fluorescence microscope is usually used to characterize the morphology, mass, or number of MPs, but compositional analysis cannot be determined with it. These fluorescence staining methods have been implemented to study MP abundance, transport, and toxicity and have been combined with other chemical characterization techniques, such as Fourier transform infrared spectroscopy and Raman spectroscopy. More studies are needed to focus on the synthesis of novel dyes to avoid NOM’s interference. They need to be combined with other spectroscopic techniques to characterize plastic composition and to develop image-analysis methods. The stability of stained MPs needs to be improved.     

Hormesis-like growth and photosynthetic physiology of marine diatom Phaeodactylum tricornutum Bohlin exposed to polystyrene microplastics

• Polystyrene microplastic caused hormesis-like effects in Phaeodactylum tricornutum. • Low concentration of microplastic promoted growth, otherwise the opposite was true. • The change trends of pigment contents were opposite at two initial algae densities. • The chlorophyll fluorescence parameters were more sensitive at low algae density. The effects of pristine polystyrene microplastics (pMPs) without any pretreatment at different concentrations (0, 10, 20, 50, and 100 mg/L) on Phaeodactylum tricornutum Bohlin at two initial algae densities (10⁵ and 10⁶ cells/mL) were assessed in this study. Hormesis-like effects were found when microalgae grew with pMPs. The results showed that pMPs inhibited microalgae growth under a high concentration of microplastics tolerated by individual algal cell (low initial algae density) (up to −80.18±9.71%) but promoted growth when the situation was opposite (up to 15.27±3.66%). The contents of photosynthetic pigments including chlorophyll a, chlorophyll c and carotenoids showed resistance to pMPs stress under a low initial algae density and increased with time, but the opposite was true under a high initial algae density. Compared with the low initial algae density group, Qp received less inhibition, and NPQ (heat dissipation) also decreased under the high initial algae density. Under the low initial algae density, OJIP parameters such as S_m, N, Area, Pi Abs, ѱ_o, φ_Eo, TRo/RC and ETo/RC were more perturbed initially and returned to the levels of the control group (without pMPs) over time, but they remained stable throughout the experiment at high initial algae density. These results show that microplastics in the marine environment may have different toxic effects on P. tricornutum at different growth stages, which is of great significance for understanding the impact of microplastics on marine microalgae and aquatic ecosystems.     

Enhancing the efficiency of nitrogen removing bacterial population to a wide range of C:N ratio (1.5:1 to 14:1) for simultaneous C & N removal

• Simultaneous C & N removal in Methammox occurs at wide C:N ratio. • Biological Nitrogen Removal at wide C:N ratio of 1.5:1 to 14:1 is not reported. • Ammonia removal shifted from mixotrophy to heterotrophy at high C:N ratio. • Acetogenic population compensated for ammonia oxidizers at high C:N ratio. • Methanogens increase the plasticity of nitrogen removers at high C:N ratio. High C:N ratio in the wastewater limits biological nitrogen removal (BNR), especially in anammox based technologies. The present study attempts to improve the COD tolerance of the BNR process by associating methanogens with nitrogen removing bacterial (NRB) populations. The new microbial system coined as ‘Methammox’, was investigated for simultaneous removal of COD (C) and ammonia (N) at C:N ratio 1.5:1 to 14:1. The ammonia removal rate (11.5 mg N/g VSS/d) and the COD removal rates (70.6 mg O/g VSS/d) of Methammox was close to that of the NRB (11.1 mg N/g VSS/d) and the methanogenic populations (77.9 mg O/g VSS/d), respectively. The activities established that these two populations existed simultaneously and independently in ‘Methammox’. Further studies in biofilm reactor fetched a balanced COD and ammonia removal (55%–60%) at a low C:N ratio (≤2:1) and high C:N ratio (≥9:1). The population abundance of methanogens was reasonably constant, but the nitrogen removal shifted from mixotrophy to heterotrophy as the C:N ratio shifted from low (C:N≤2:1) to high (C:N≥9:1). The reduced autotrophic NRB (ammonia- and nitrite-oxidizing bacteria and Anammox) population at a high C:N ratio was compensated by the fermentative group that could carry out denitrification heterotrophically. The functional plasticity of the Methammox system to adjust to a broad C:N ratio opens new frontiers in biological nitrogen removal of high COD containing wastewaters.     

Determination of 27 pharmaceuticals and personal care products (PPCPs) in water: The benefit of isotope dilution

• Isotope dilution method was developed for the determination of 27 PPCPs in water. • The established method was successfully applied to different types of water samples. • The correction effect of corresponding 27 ILSs over 70 d was investigated. • Benefit of isotopic dilution method was illustrated for three examples. Pharmaceuticals and personal care products (PPCPs) are a unique group of emerging and non-persistent contaminants. In this study, 27 PPCPs in various water samples were extracted by solid phase extraction (SPE), and determined by isotope dilution method using liquid chromatography coupled to tandem triple quadruple mass spectrometer (LC-MS/MS). A total of 27 isotopically labeled standards (ILSs) were applied to correct the concentration of PPCPs in spiked ultrapure water, drinking water, river, effluent and influent sewage. The corrected recoveries were 73%–122% with the relative standard deviation (RSD)<16%, except for acetaminophen. The matrix effect for all kinds of water samples was<22% and the method quantitation limits (MQLs) were 0.45–8.6 ng/L. The developed method was successfully applied on environmental water samples. The SPE extracts of spiked ultrapure water, drinking water, river and wastewater effluent were stored for 70 days, and the ILSs-corrected recoveries of 27 PPCPs were obtained to evaluate the correction ability of ILSs in the presence of variety interferences. The recoveries of 27 PPCPs over 70 days were within the scope of 72%–140% with the recovery variation<37% in all cases. The isotope dilution method seems to be of benefit when the extract has to be stored for long time before the instrument analysis.     

Fabrication of highly efficient Bi2WO6/CuS composite for visible-light photocatalytic removal of organic pollutants and Cr(VI) from wastewater

• A novel Bi₂WO₆/CuS composite was fabricated by a facile solvothermal method. • This composite efficiently removed organic pollutants and Cr(VI) by photocatalysis. • The DOM could promoted synchronous removal of organic pollutants and Cr(VI). • This composite could be applied at a wide pH range in photocatalytic reactions. • Possible photocatalytic mechanisms of organic pollutants and Cr(VI) were proposed. A visible-light-driven Bi₂WO₆/CuS p-n heterojunction was fabricated using an easy solvothermal method. The Bi₂WO₆/CuS exhibited high photocatalytic activity in a mixed system containing rhodamine B (RhB), tetracycline hydrochloride (TCH), and Cr (VI) under natural conditions. Approximately 98.8% of the RhB (10 mg/L), 87.6% of the TCH (10 mg/L) and 95.1% of the Cr(VI) (15 mg/L) were simultaneously removed from a mixed solution within 105 min. The removal efficiencies of TCH and Cr(VI) increased by 12.9% and 20.4%, respectively, in the mixed solution, compared with the single solutions. This is mainly ascribed to the simultaneous consumption electrons and holes, which increases the amount of excited electrons/holes and enhances the separation efficiency of photogenerated electrons and holes. Bi₂WO₆/CuS can be applied over a wide pH range (2–6) with strong photocatalytic activity for RhB, TCH and Cr(VI). Coexisiting dissolved organic matter in the solution significantly promoted the removal of TCH (from 74.7% to 87.2%) and Cr(VI) (from 75.7% to 99.9%) because it accelerated the separation of electrons and holes by consuming holes as an electron acceptor. Removal mechanisms of RhB, TCH, and Cr(VI) were proposed, Bi₂WO₆/CuS was formed into a p-n heterojunction to efficiently separate and transfer photoelectrons and holes so as to drive photocatalytic reactions. Specifically, when reducing pollutants (e.g., TCH) and oxidizing pollutants (e.g., Cr(VI)) coexist in wastewater, the p-n heterojunction in Bi₂WO₆/CuS acts as a “bridge” to shorten the electron transport and thus simultaneously increase the removal efficiencies of both types of pollutants.     

Distribution,characteristics and daily fluctuations of microplastics throughout wastewater treatment plants with mixed domestic–industrial influents in Wuxi City,China

• MPs were analyzed throughout three WWTPs with mixed domestic–industrial influents. • White polyethylene granules from plastic manufacturing were the most dominant MPs. • MPs abundance in random grab-sampling was lower than that in daily dense sampling. • The production of MPs such as microbeads need to be restricted from the source. In wastewater treatment plants (WWTPs), microplastics (MPs) are complex, especially with mixed domestic–industrial influents. Conventional random grab sampling can roughly depict the distribution and characteristics of MPs but can not accurately reflect their daily fluctuations. In this study, the concentration, shape, polymer type, size, and color of MPs were analyzed by micro-Raman spectroscopy (detection limit of 0.05 mm) throughout treatment stages of three mixed domestic–industrial WWTPs (W1, W2, and W3) in Wuxi City, China, and the daily fluctuations of MPs were also obtained by dense grab sampling within 24 h. For influent samples, the average MP concentration of 392.2 items/L in W1 with 10% industrial wastewater was much higher than those in W2 (71.2 items/L with 10% industrial wastewater) and W3 (38.3 items/L with 60% industrial wastewater). White polyethylene granules with a diameter less than 0.5 mm from plastic manufacturing were the most dominant MPs in the influent of W1, proving the key role of industrial sources in MPs pollution. In addition, the daily dense sampling results showed that MP concentration in W1 influent fluctuated widely between 29.1 items/L and 4617.6 items/L within a day. Finally, few MPs (less than 4.0 items/L) in these WWTPs effluents were attributed to the effective removal of wastewater treatment processes. Thus, further attention should be paid to regulating the primary sources of MPs.     

Effects of ambient temperature on regulated gaseous and particulate emissions from gasoline-, E10- and M15-fueled vehicles

• Emissions from two sedans were tested with gasoline, E10 and M15 at 30°C and -7°C. • As the temperature decreased, the PM, PN and BC emissions increased with all fuels. • Particulate emissions with E10 and M15 were more sensitive to the temperature. • The PN and BC generated during cold start-up dominated those over the WLTC. Ambient temperature has substantial impacts on vehicle emissions, but the impacts may differ between traditional and alcohol gasolines. The objective of this study was to investigate the effects of temperature on gaseous and particulate emissions with both traditional and alcohol gasoline. Regulated gaseous, particle mass (PM), particle number (PN) and black carbon (BC) emissions from typical passenger vehicles were separately quantified with gasoline, E10 (10% ethanol and 90% gasoline by volume) and M15 (15% methanol and 85% gasoline by volume) at both 30°C and -7°C. The particulate emissions with all fuels increased significantly with decreased temperature. The PM emissions with E10 were only 48.0%–50.7% of those with gasoline at 30°C but increased to 59.2%-79.4% at -7°C. The PM emissions with M15 were comparable to those with gasoline at 30°C, but at -7°C, the average PM emissions were higher than those with gasoline. The variation trend of PN emissions was similar to that of PM emissions with changes in the fuel and temperature. At 30°C, the BC emissions were lower with E10 and M15 than with gasoline in most cases, but E10 and M15 might emit more BC than gasoline at -7°C, especially M15. The results of the transient PN and BC emission rates show that particulate emissions were dominated mainly by those emitted during the cold-start moment. Overall, the particulate emissions with E10 and M15 were more easily affected by ambient temperature, and the advantages of E10 and M15 in controlling particulate emissions declined as the ambient temperature decreased.     

Less attention paid to waterborne SARS-CoV-2 spreading in Beijing urban communities

• A survey on individual’s perception of SARS-CoV-2 transmission was conducted. • Waterborne transmission risks are far less perceived by individuals. • Precautions of preventing wastewater mediated transmission are implemented. • The precautions for wastewater transmission are less favored by the public. • Education level differs the most regarding to waterborne transmission perception. SARS-CoV-2 has been detected in various environmental media. Community and individual-engaged precautions are recommended to stop or slow environmentally-mediated transmission. To better understand the individual’s awareness of and precaution to environmental dissemination of SARS-CoV-2, an online survey was conducted in Beijing during March 14–25, 2020. It is found that the waterborne (especially wastewater mediated) spreading routes are far less perceived by urban communities. The precautions for wastewater transmission are less favored by the public than airborne and solid waste mediated spreading routes. Such risk communication asymmetry in waterborne transmission will be further enlarged in places with fragile water system. Furthermore, education level is the most significant attribution (Sig.<0.05) that causes the difference of awareness and precautions of the waterborne transmission among the respondents, according to the variance analysis results. Our survey results emphasize the urgent need for evidence-based, multifactorial precautions for current and future outbreaks of COVID-19.