Organophosphate esters in sediment from Taihu Lake,China: Bridging the gap between riverine sources and lake sinks

• Eleven OPEs were detected in river sediment and lake sediment in Taihu Lake. • TnBP dominated in river sediment, while TBEP dominated in lake sediment. • A strong correlation existed between logK_oc and logK_ow of OPEs. • Vertical profiles of OPEs in sediment cores varied according to sampling location. Surface sediment samples from Taihu Lake in China and its inflow rivers, along with two lake sediment core samples, were collected and analyzed for organophosphate esters (OPEs). The concentrations of total OPEs varied from 28.60 ng/g to 158.72 ng/g (median: 54.25 ng/g) in river surface sediment and from 62.57 ng/g to 326.84 ng/g (median: 86.37 ng/g) in lake sediment. Tributyl phosphate (TnBP) was the predominant compound in river surface sediment, and tris(2-butoxyethyl) phosphate was predominant in lake sediment. High contamination occurred in the north-west region, which was related to the high level of urbanization and high usage of OPEs. The sediment–water partition coefficients of OPEs (logK_oc) were calculated, showing a significant correlation with logK_ow (p<0.05). The concentration and composition of OPEs in two sediment cores varied due to the different sampling locations, with more OPE species found in the northern region than in the southern one. Principal component analysis and positive matrix factorization indicated that sewage discharges, vehicle emissions, and atmospheric deposition were the possible sources of OPEs in Taihu Lake sediments. Tris(1-chloro-2-propyl) phosphate, tris(2-chloroethyl) phosphate, and TnBP were the main OPEs causing ecological risks.     

Identification of sources,characteristics and photochemical transformations of dissolved organic matter with EEM-PARAFAC in the Wei River of China

• The source of DOM in surface water and sediment is inconsistent. • The DOC content changes differently in surface water and sediment. • The content of DOC in the surface water is lower than that in the sediment. • The DOM in the surface water had higher photodegradation potentials than sediment. Dissolved organic matter (DOM) in rivers is a critical regulator of the cycling and toxicity of pollutants and the behavior of DOM is a key indicator for the health of the environment. We investigated the sources and characteristics of DOM in surface water and sediment samples of the Wei River, China. Dissolved organic carbon (DOC) concentration and ultraviolet absorbance at 254 nm (UV₂₅₄) increased in the surface water and were decreased in the sediment downstream, indicating that the source of DOM in the water differed from the sediment. Parallel factor (PARAFAC) analysis of the excitation-emission matrices (EEM) revealed the presence of terrestrial humus-like, microbial humus-like and tryptophan-like proteins in the surface water, whereas the sediment contained UVA humic-like, UVC humic-like and fulvic-like in the sediment. The DOM in the surface water and sediment were mainly derived from microbial metabolic activity and the surrounding soil. Surface water DOM displayed greater photodegradation potential than sediment DOM. PARAFAC analysis indicated that the terrestrial humic-like substance in the water and the fulvic-like component in the sediment decomposed more rapidly. These data describe the characteristics of DOM in the Wei River and are crucial to understanding the fluctuations in environmental patterns.     

Sustainable wood-based nanotechnologies for photocatalytic degradation of organic contaminants in aquatic environment

•Wood and its reassemblies are ideal substrates to develop novel photocatalysts. •Synthetic methods and mechanisms of wood-derived photocatalysts are summarized. •Advances in wood-derived photocatalysts for organic pollutant removal are summed up. •Metal doping, morphology control and semiconductor coupling methods are highlighted. •Structure-activity relationship and catalytic mechanism of photocatalysts are given. Wood-based nanotechnologies have received much attention in the area of photocatalytic degradation of organic contaminants in aquatic environment in recent years, because of the high abundance and renewability of wood as well as the high reaction activity and unique structural features of these materials. Herein, we present a comprehensive review of the current research activities centering on the development of wood-based nanocatalysts for photodegradation of organic pollutants. This review begins with a brief introduction of the development of photocatalysts and hierarchical structure of wood. The review then focuses on strategies of designing novel photocatalysts based on wood or its recombinants (such as 1D fiber, 2D films and 3D porous gels) using advanced nanotechnology including sol-gel method, hydrothermal method, magnetron sputtering method, dipping method and so on. Next, we highlight typical approaches that improve the photocatalytic property, including metal element doping, morphology control and semiconductor coupling. Also, the structure-activity relationship of photocatalysts is emphasized. Finally, a brief summary and prospect of wood-derived photocatalysts is provided.     

Quantification of pesticide residues on plastic mulching films in typical farmlands of the North China

• Pesticide residuals on mulching film of Shandong, Tianjin and Hebei. • Detected 29 pesticides in soil and 30 in mulching film. • Pesticides on plastic films: 86.4‒22213.2 ng/g and in soil: 9.3‒535.3 ng/g. • Pesticides on plastic films 20 times higher than in soil. Plastic debris as new pollutants attracts much attention in the recent years. The plastic mulching films is one of the most important plastic debirs source in the environment. The aim of this work was to investigate the current status of pesticide residues on the plastic mulching films. Based on the QuEChERS method, multi-residue methods for detection of pesticide residues with gas chromatography tandem mass spectrum (GC-MS) and high performance liquid chromatography tandem mass spectrum (HPLC-MS) were developed for the analysis of the pesticides residues in plastic film and soil samples from Tianjin, Hebei and Shandong. The total concentrations of pesticide residues were in the range of 86.4‒22213.2 ng/g in plastic film debris, which was about 20 times higher than that in soil (9.3‒535.3 ng/g). Residual level of pesticides varied greatly in different samples. The historical usage and recent application of pesticides were the main sources for pesticide residues on plastic films and soil. In short, plastic mulching films could act as a sink for pesticides in farmland and the ubiquitous pesticide residues on plastic films should draw more attention.     

Phosphorus transformation under the influence of aluminum,organic carbon,and dissolved oxygen at the water-sediment interface: A simulative study

• The three simulation factors caused various changes in both water and sediment. • Responses to simulations differed with the reported natural lakes and wetlands. • Al has dominant effects on sediment P release control among the three factors. • Adding sediment Al can be effective and safe under the simulated conditions. • Polyphosphates were not generated, while added phytate was rather stable. The effects of sediment aluminum (Al), organic carbon (OC), and dissolved oxygen (DO) on phosphorus (P) transformation, at the water-sediment interface of a eutrophic constructed lake, were investigated via a series of simulative experiments. The above three factors had various influences on dissolved P concentration, water pH, water and surface sediment appearance, and P fractions. Additions of Al had the greatest effect on suppressing P release, and the water pH remained alkaline in the water-sediment system under various OC and DO conditions. No dissolution of the added Al was detected. ³¹P-NMR characterization suggested that OC addition did not promote biological P uptake to polyphosphates under oxic conditions. The simulation result on the added phytate indicated the absence of phytate in the original lake sediment. As compared to the reported natural lakes and wetland, the water-sediment system of the constructed lake responded differently to some simulative conditions. Since Al, OC, and DO can be controlled with engineering methods, the results of this study provide insights for the practical site restorations.     

Reactivity of Pyrogenic Carbonaceous Matter (PCM) in mediating environmental reactions: Current knowledge and future trends

• Pyrogenic Carbonaceous Matter (PCM) promote both chemical and microbial synergies. • Discussion of PCM-enhanced abiotic transformation pathways of organic pollutants. • Conjugated microporous polymers (CMPs) can mimic the performance of PCM. • CMPs offer a platform that allows for systematic variation of individual properties. Pyrogenic Carbonaceous matter (PCM; e.g., black carbon, biochar, and activated carbon) are solid residues from incomplete combustion of fossil fuel or biomass. They are traditionally viewed as inert adsorbents for sequestering contaminants from the aqueous phase or providing surfaces for microbes to grow. In this account, we reviewed the recently discovered reactivity of PCM in promoting both chemical and microbial synergies that are important in pollutant transformation, biogeochemical processes of redox-active elements, and climate change mitigation with respect to the interaction between biochar and nitrous oxide (N₂O). Moreover, we focused on our group’s work in the PCM-enhanced abiotic transformation of nitrogenous and halogenated pollutants and conducted in-depth analysis of the reaction pathways. To understand what properties of PCM confer its reactivity, our group pioneered the use of PCM-like polymers, namely conjugated microporous polymers (CMPs), to mimic the performance of PCM. This approach allows for the controlled incorporation of specific surface properties (e.g., quinones) into the polymer network during the polymer synthesis. As a result, the relationship between specific characteristics of PCM and its reactivity in facilitating the decay of a model pollutant was systematically studied in our group’s work. The findings summarized in this account help us to better understand an overlooked environmental process where PCM synergistically interacts with various environmental reagents such as hydrogen sulfide and water. Moreover, the knowledge gained in these studies could inform the design of a new generation of reactive carbonaceous materials with tailored properties that are highly efficient in contaminant removal.     

Techno-economic characteristics of wastewater treatment plants retrofitted from the conventional activated sludge process to the membrane bioreactor process

• Retrofitting from CAS to MBR increased effluent quality and environmental benefits. • Retrofitting from CAS to MBR increased energy consumption but not operating cost. • Retrofitting from CAS to MBR increased the net profit and cost efficiency. • The advantage of MBR is related to the adopted effluent standard. • The techno-economy of MBR improves with stricter effluent standards. While a growing number of wastewater treatment plants (WWTPs) are being retrofitted from the conventional activated sludge (CAS) process to the membrane bioreactor (MBR) process, the debate on the techno-economy of MBR vs. CAS has continued and calls for a thorough assessment based on techno-economic valuation. In this study, we analyzed the operating data of 20 large-scale WWTPs (capacity≥10000 m³/d) and compared their techno-economy before and after the retrofitting from CAS to MBR. Through cost-benefit analysis, we evaluated the net profit by subtracting the operating cost from the environmental benefit (estimated by the shadow price of pollutant removal and water reclamation). After the retrofitting, the removal rate of pollutants increased (e.g., from 89.0% to 93.3% on average for NH₃-N), the average energy consumption increased from 0.40 to 0.57 kWh/m³, but the operating cost did not increase significantly. The average marginal environmental benefit increased remarkably (from 0.47 to 0.66 CNY/g for NH₃-N removal), leading to an increase in the average net profit from 19.4 to 24.4 CNY/m³. We further scored the technical efficiencies via data envelopment analysis based on non-radial directional distance functions. After the retrofitting, the relative cost efficiency increased from 0.70 to 0.73 (the theoretical maximum is 1), while the relative energy efficiency did not change significantly. The techno-economy is closely related to the effluent standard adopted, particularly when truncating the extra benefit of pollutant removal beyond the standard in economic modeling. The modeling results suggested that MBR is more profitable than CAS given stricter effluent standards.     

Size and shape effects of MnFe2O4 nanoparticles as catalysts for reductive degradation of dye pollutants

• Size and shape-dependent MnFe₂O₄ NPs were prepared via a facile method. • Ligand-exchange chemistry was used to prepare the hydrophilic MnFe₂O₄ NPs. • The catalytic properties of MnFe₂O₄ NPs toward dye degradation were fully studied. • The catalytic activities of MnFe₂O₄ NPs followed Michaelis–Menten behavior. • All the MnFe₂O₄ NPs exhibit selective degradation to different dyes. The magnetic nanoparticles that are easy to recycle have tremendous potential as a suitable catalyst for environmental toxic dye pollutant degradation. Rationally engineering shapes and tailoring the size of nanocatalysts are regarded as an effective manner for enhancing performances. Herein, we successfully synthesized three kinds of MnFe₂O₄ NPs with distinctive sizes and shapes as catalysts for reductive degradation of methylene blue, rhodamine 6G, rhodamine B, and methylene orange. It was found that the catalytic activities were dependent on the size and shape of the MnFe₂O₄ NPs and highly related to the surface-to-volume ratio and atom arrangements. Besides, all these nanocatalysts exhibit selectivity to different organic dyes, which is beneficial for their practical application in dye pollutant treatment. Furthermore, the MnFe₂O₄ NPs could be readily recovered by a magnet and reused more than ten times without appreciable loss of activity. The size and shape effects of MnFe₂O₄ nanoparticles demonstrated in this work not only accelerate further understanding the nature of nanocatalysts but also contribute to the precise design of nanoparticles catalyst for pollutant degradation.     

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.     

Excitation-emission matrix (EEM) fluorescence spectroscopy for characterization of organic matter in membrane bioreactors: Principles,methods and applications

• Principles and methods for fluorescence EEM are systematically outlined. • Fluorophore peak/region/component and energy information can be extracted from EEM. • EEM can fingerprint the physical/chemical/biological properties of DOM in MBRs. • EEM is useful for tracking pollutant transformation and membrane retention/fouling. • Improvements are still needed to overcome limitations for further studies. The membrane bioreactor (MBR) technology is a rising star for wastewater treatment. The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter (DOM) in the system. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, a powerful tool for the rapid and sensitive characterization of DOM, has been extensively applied in MBR studies; however, only a limited portion of the EEM fingerprinting information was utilized. This paper revisits the principles and methods of fluorescence EEM, and reviews the recent progress in applying EEM to characterize DOM in MBR studies. We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity, wavelength regional distribution, and spectral deconvolution (giving fluorescent component loadings/scores), and discussed how to use the information to interpret the chemical compositions, physiochemical properties, biological activities, membrane retention/fouling behaviors, and migration/transformation fates of DOM in MBR systems. In addition to conventional EEM indicators, novel fluorescent parameters are summarized for potential use, including quantum yield, Stokes shift, excited energy state, and fluorescence lifetime. The current limitations of EEM-based DOM characterization are also discussed, with possible measures proposed to improve applications in MBR monitoring.     

Fate and risk assessment of emerging contaminants in reclaimed water production processes

• PPCPs had the highest removal efficiency in A²O combined with MBR process (86.8%). • ARGs and OPFRs were challenging to remove (6.50% and 31.0%, respectively). • Octocrylene and tris(2-ethylhexyl) phosphate posed high risks to aquatic organisms. • Meta-analysis was used to compare the ECs removal in wastewater treatment. • Membrane treatment technology is the most promising treatment for ECs removal. Reclaimed water has been widely applied in irrigation and industrial production. Revealing the behavior of emerging contaminants in the production process of reclaimed water is the first prerequisite for developing relevant water quality standards. This study investigated 43 emerging contaminants, including 22 pharmaceuticals and personal care products (PPCPs), 11 organophosphorus flame retardants (OPFRs), and 10 antibiotic resistance genes (ARGs) in 3 reclaimed wastewater treatment plants (RWTPs) in Beijing. The composition profiles and removal efficiencies of these contaminants in RWTPs were determined. The results indicated that the distribution characteristics of the different types of contaminants in the three RWTPs were similar. Caffeine, sul2 and tris(1-chloro-2-propyl) phosphate were the dominant substances in the wastewater, and their highest concentrations were 27104 ng/L, 1.4 × 10⁷ copies/mL and 262 ng/L, respectively. Ofloxacin and sul2 were observed to be the dominant substances in the sludge, and their highest concentrations were 5419 ng/g and 3.7 × 10⁸ copies/g, respectively. Anaerobic/anoxic/oxic system combined with the membrane bioreactor process achieved a relatively high aqueous removal of PPCPs (87%). ARGs and OPFRs were challenging to remove, with average removal rates of 6.5% and 31%, respectively. Quantitative meta-analysis indicated that tertiary treatment processes performed better in emerging contaminant removal than secondary processes. Diethyltoluamide exhibited the highest mass load discharge, with 33.5 mg/d per 1000 inhabitants. Octocrylene and tris(2-ethylhexyl) phosphate posed high risks (risk quotient>1.0) to aquatic organisms. This study provides essential evidence to screen high priority pollutants and develop corresponding standard in RWTPs.     

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.     

Degradation of refractory organics in concentrated leachate by the Fenton process: Central composite design for process optimization

• 90% total COD, 95.3% inert COD and 97.2% UV₂₅₄ were removed. • High R² values (over 95%) for all responses were obtained with CCD. • Operational cost was calculated to be 0.238 €/g COD_removed for total COD removal. • Fenton oxidation was highly-efficient method for inert COD removal. • BOD₅/COD ratio of leachate concentrate raised from 0.04 to 0.4. The primary aim of this study is inert COD removal from leachate nanofiltration concentrate because of its high concentration of resistant organic pollutants. Within this framework, this study focuses on the treatability of leachate nanofiltration concentrate through Fenton oxidation and optimization of process parameters to reach the maximum pollutant removal by using response surface methodology (RSM). Initial pH, Fe²⁺ concentration, H₂O₂/Fe²⁺ molar ratio and oxidation time are selected as the independent variables, whereas total COD, color, inert COD and UV₂₅₄ removal are selected as the responses. According to the ANOVA results, the R² values of all responses are found to be over 95%. Under the optimum conditions determined by the model (pH: 3.99, Fe²⁺: 150 mmol/L, H₂O₂/Fe²⁺: 3.27 and oxidation time: 84.8 min), the maximum COD removal efficiency is determined as 91.4% by the model. The color, inert COD and UV₂₅₄ removal efficiencies are determined to be 99.9%, 97.2% and 99.5%, respectively, by the model, whereas the total COD, color, inert COD and UV₂₅₄ removal efficiencies are found respectively to be 90%, 96.5%, 95.3% and 97.2%, experimentally under the optimum operating conditions. The Fenton process improves the biodegradability of the leachate NF concentrate, increasing the BOD₅/COD ratio from the value of 0.04 to the value of 0.4. The operational cost of the process is calculated to be 0.238 €/g COD_removed. The results indicate that the Fenton oxidation process is an efficient and economical technology in improvement of the biological degradability of leachate nanofiltration concentrate and in removal of resistant organic pollutants.     

Magnetotactic bacteria: Characteristics and environmental applications

• Magnetotactic bacteria (MTB) synthesize magnetic nanoparticle within magnetosomes. • The morphologic and phylogenetic diversity of MTB were summarized. • Isolation and mass cultivation of MTB deserve extensive research for applications. • MTB can remove heavy metals, radionuclides, and organic pollutants from wastewater. Magnetotactic bacteria (MTB) are a group of Gram-negative prokaryotes that respond to the geomagnetic field. This unique property is attributed to the intracellular magnetosomes, which contains membrane-bound nanocrystals of magnetic iron minerals. This review summarizes the most recent advances in MTB, magnetosomes, and their potential applications especially the environmental pollutant control or remediation. The morphologic and phylogenetic diversity of MTB were first introduced, followed by a critical review of isolation and cultivation methods. Past research has devoted to optimize the factors, such as oxygen, carbon source, nitrogen source, nutrient broth, iron source, and mineral elements for the growth of MTB. Besides the applications of MTB in modern biological and medical fields, little attention was made on the environmental applications of MTB for wastewater treatment, which has been summarized in this review. For example, applications of MTB as adsorbents have resulted in a novel magnetic separation technology for removal of heavy metals or organic pollutants in wastewater. In addition, we summarized the current advance on pathogen removal and detection of endocrine disruptor which can inspire new insights toward sustainable engineering and practices. Finally, the new perspectives and possible directions for future studies are recommended, such as isolation of MTB, genetic modification of MTB for mass production and new environmental applications. The ultimate objective of this review is to promote the applications of MTB and magnetosomes in the environmental fields.     

Particle-bound polycyclic aromatic hydrocarbons in typical urban of Yunnan-Guizhou Plateau: Characterization,sources and risk assessment

• The sampling was conducted in city on the Yunnan-Guizhou Plateau for one year. • The groups of PAHs revealed their different environmental fates and migration paths. • Seasonal biomass burning could affect the concentration by long-distance transport. • Industrial sources and traffic emissions were the main contributor of PAHs. • Living in industrial areas or winter had higher health risk by exposure PAHs in PM_2.5. Monthly particle-phase ambient samples collected at six sampling locations in Yuxi, a high-altitude city on the edge of Southeast Asia, were measured for particle-associated PAHs. As trace substances, polycyclic aromatic hydrocarbons (PAHs) are susceptible to the influences of meteorological conditions, emissions, and gas-particulate partitioning and it is challenging job to precise quantify the source and define the transmission path. The daily concentrations of total PM_2.5-bound PAHs ranged from 0.65 to 80.76 ng/m³, with an annual mean of 11.94 ng/m³. Here, we found that the concentration of PM_2.5-bound PAHs in winter was significantly higher than that in summer, which was mainly due to source and meteorology influence. The increase of fossil combustion and biomass burning in cold season became the main contributors of PAHs, while precipitation and low temperature exacerbated this difference. According to the concentration variation trend of PM_2.5-bound PAHs and their relationship with meteorological conditions, a new grouping of PAHs is applied, which suggested that PAHs have different environmental fates and migration paths. A combination of source analysis and trajectory model supported local sources from combustion of fossil fuel and vehicle exhaust contributed to the major portion on PAHs in particle, but on the Indochina Peninsula the large number of pollutants emitted by biomass burning during the fire season would affect the composition of PAHs through long-range transporting. Risk assessment in spatial and temporal variability suggested that citizens living in industrial areas were higher health risk caused by exposure the PM_2.5-bound PAHs than that in other regions, and the risk in winter was three times than in summer.     

Significant increase of assimilable organic carbon (AOC) levels in MBR effluents followed by coagulation,ozonation and combined treatments: Implications for biostability control of reclaimed water

• Annual AOCs in MBR effluents were stable with small increase in warmer seasons. • Significant increase in AOC levels of tertiary effluents were observed. • Coagulation in prior to ozonation can reduce AOC formation in tertiary treatment. • ∆UV₂₅₄ and SUVA can be surrogates to predict the AOC changes during ozonation. As water reuse development has increased, biological stability issues associated with reclaimed water have gained attention. This study evaluated assimilable organic carbon (AOC) in effluents from a full-scale membrane biological reactor (MBR) plant and found that they were generally stable over one year (125–216 µg/L), with slight increases in warmer seasons. After additional tertiary treatments, the largest increases in absolute and specific AOCs were detected during ozonation, followed by coagulation-ozonation and coagulation. Moreover, UV₂₅₄ absorbance is known to be an effective surrogate to predict the AOC changes during ozonation. Applying coagulation prior to ozonation of MBR effluents for removal of large molecules was found to reduce the AOC formation compared with ozonation treatment alone. Finally, the results revealed that attention should be paid to seasonal variations in influent and organic fraction changes during treatment to enable sustainable water reuse.     

Performance evaluation on the pollution control against wet weather overflow based on on-site coagulation/flocculation in terminal drainage pipes

• A way for overflow control based on on-site coagulation/flocculation was proposed. • Coagulant and flocculant dose were optimized based on pollutant removal performance. • Settling time of 5 min is enough in a proper transmission distance. • Fast removal of particulate pollutants could be achieved under varied flow. The pollution caused by wet weather overflow in urban drainage systems is a main factor causing blackening an odorization of urban rivers. The conventional overflow treatment based on coagulation/flocculation in terminal drainage systems requires relatively large space and long retention time demand that makes it not applicable in crowded urban drainage systems or under heavy rains. On-site coagulation/flocculation in terminal drainage pipes was proposed in this study which was aimed to transfer the coagulation/flocculation process to the inside of pipes at the terminal drainage system to save space and reduce the retention time of the coagulation/flocculation process. The optimized dose of chemicals was studied first which was 80 mg/L of coagulant and 0.8 mg/L of flocculant. Settling for only 5 min can remove most of the pollutants at 406.5 m of transmission distance. In addition, the relation of wet weather overflow rate and concentration of pollution load on the on-site coagulation/flocculation process was investigated, which indicated that high removal of pollutant was gained at a large range of flow velocity and pollutant concentration. Finally, the study confirmed electric neutralization, bridging, and net capture as the major mechanisms in this process, and further optimization was proposed. The proposed process can reduce much turbidity, chemical oxygen demand, and total phosphorous, but hardly remove soluble ammonia and organics. This work provides scientific guidance to address wet weather overflow in terminal drainage pipes.     

Evaluating heavy metal contamination of riverine sediment cores in different land-use areas

• Metal pollution was studied in riverine sediments from different land-use areas. • Cd was the most serious heavy metal contaminant in riverine sediment cores. • Riverine sediment cores from industrial area were most polluted by heavy metals. • B1 fraction determined metal pollution, risk and toxicity in riverine sediments. Anthropogenic activities are regarded as the main sources of heavy metal pollution, yet few studies have investigated the effects of land-use setting on heavy metal accumulation in riverine sediments. Based on both total contents and geochemical fractions, heavy metal pollution, risk and toxicity were determined in riverine sediment cores from different land-use areas (mountain area- MA, farm area- FA, city area- CA, and industrial area- IA) of the Yang River Basin in North China. The results showed that FA had higher contents of riverine sedimentary Cu; CA had higher contents of Cd; IA had higher contents of both Cd and Zn. Most riverine sediments from FA and IA were contaminated with the investigated metals, although these concentrations were evaluated to have low potential ecological risk and no toxicity to benthic organisms. However, a high proportion of Cd in the B1 fraction of riverine sediments in IA indicating high risk should receive more attention. The B1 fraction largely determined the contamination, risk and toxicity levels associated with heavy metals in the riverine sediments of the Yang River Basin.     

Crosslinking acrylamide with EDTA-intercalated layered double hydroxide for enhanced recovery of Cr(VI) and Congo red: Adsorptive and mechanistic study

• Functional groups of AM and EDTA in composite increased removal of Cr(VI) and CR. • Removal process reached equilibrium within 30 min and was minimally affected by pH. • Elimination of Cr(VI) was promoted by coexisting CR. • Adsorption process of CR was less influenced by the presence of Cr(VI). • Mechanisms were electrostatic attraction, surface complexation and anion exchange. We prepared ethylenediaminetetraacetic acid (EDTA)-intercalated MgAl-layered double hydroxide (LDH-EDTA), then grafted acrylamide (AM) to the LDH-EDTA by a cross-linking method to yield a LDH-EDTA-AM composite; we then evaluated its adsorptive ability for Congo red (CR) and hexavalent chromium (Cr(VI)) in single and binary adsorption systems. The adsorption process on LDH-EDTA-AM for CR and Cr(VI) achieved equilibrium quickly, and the removal efficiencies were minimally affected by initial pH. The maximum uptake quantities of CR and Cr(VI) on LDH-EDTA-AM were 632.9 and 48.47 mg/g, respectively. In mixed systems, chromate removal was stimulated by the presence of CR, while the adsorption efficiency of CR was almost not influenced by coexisting Cr(VI). The mechanisms involved electrostatic attraction, surface complexation, and anion exchange for the adsorption of both hazardous pollutants. In the Cr(VI) adsorption process, reduction also took place. The removal efficiencies in real contaminated water were all higher than those in the laboratory solutions.     

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.