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Adsorption fractionation of dissolved organic matter (DOM) induced by soil minerals is a common geochemical process, which has been widely documented on natural DOM. Hydrochar is a promising functional material in soil remediation but can continuously release abundant endogenic DOM with potential biotoxicity. However, adsorption fractionation at molecular level and its influence on toxicity evolution of hydrochar-derived DOM (HDOM) at genetic level at the soil-water interface remain poorly understood. Herein, we investigated the molecular fractionation of HDOM on three typical soil iron minerals (i.e., ferrihydrite, goethite, and hematite). Results from ultrahigh-resolution mass spectrum showed that HDOM molecules with high molecular weight and high contents of unsaturated oxidized or aromatic structures (e.g., unsaturated phenolic compounds, polyphenols, and organic acids) were preferentially absorbed by iron oxyhydroxides, while aliphatic molecules and poorly oxygenated compounds (e.g., hydrocarbon, phenols, and alcohols) were retained in aqueous phase. Furthermore, we quantitatively evaluated their genotoxicity variation using a toxicogenomics assay using green fluorescence protein-fused whole-cell array, and results showed that oxidative, protein, membrane, and DNA stresses were primary responses upon exposure to original HDOM. Interface fractionation induced by iron oxyhydroxides significantly reduced genotoxicity of HDOM, especially for oxidative, membrane and DNA stresses. Overall, the selective absorption of HDOM molecules by iron oxyhydroxides shifted its biotoxicity, which might change the ecological effects of hydrochar amendment, e.g., microbial community structure, environmental pollutant transformation, and even the ecological function of terrestrial and aquatic ecosystems. These findings would contribute to unraveling the environmental geochemistry process of HDOM in the natural soil-water interface and provide a new insight into the biotoxicity of hydrochar usage to terrestrial and aquatic environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Antibiotic pollution in water environment is an emerging threat to plant health. Developing efficient strategies to reassemble the antibiotic-tolerating endophytes will confer fitness benefits on host plants to alleviate antibiotic stress. Here, introducing environmental microbes was proved as a promising approach to reshape the antibiotic-tolerating plant endophytes under antibiotic stress in aquatic microcosms. The introduction of environmental microbes effectively relieved antibiotic-driven perturbation on plant endophytes, with reduced changes in bacterial diversity and differential bacterial taxa and functional genes. Moreover, introducing environmental microbes facilitated the enrichment of endophytic bacterial genera and functional genes related to drug metabolism, which possessed the potentials to degrade antibiotics. In addition, environmental microbes boosted antibiotic-reshaped endophytes to form more stable bacterial networks for stronger antibiotic tolerance. In consequence, the decreased growth inhibition of antibiotics on host plants and enhanced antibiotic removal from microcosms were achieved by introducing environmental microbes. These findings pursue environmental microbes as practical resources to assist plants in reshaping the stress-alleviating endophytes, potentially improving plant tolerance to water pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Wolframite (FeWO 4 ), a typical polyoxometalate, serves as an auspicious candidate for heterogeneous catalysts, courtesy of its high chemical stability and electronic properties. However, the electron-deficient surface-active Fe species in FeWO 4 are insufficient to cleave H 2 O 2 via Fe redox-mediated Fenton-like catalytic reaction. Herein, we doped Sulfur (S) atom into FeWO 4 catalysts to refine the electronic structure of FeWO 4 for H 2 O 2 activation and sulfamethoxazole (SMX) degradation. Furthermore, spin-state reconstruction on S-doped FeWO 4 was found to effectively refine the electronic structure of Fe in the d orbital, thereby enhancing H 2 O 2 activation. S doping also accelerated electron transfer during the conversion of sulfur species, promoting the cycling of Fe(III) to Fe(II). Consequently, S-doped FeWO 4 bolstered the Fenton-like reaction by nearly two orders of magnitude compared to FeWO 4 . Significantly, the developed S-doped FeWO 4 exhibited a remarkable removal efficiency of approximately 100% for SMX within 40 min in real water samples. This underscores its extensive pH adaptability, robust catalytic stability, and leaching resistance. The matrix effects of water constituents on the performance of S-doped FeWO 4 were also investigated, and the results showed that a certain amount of Cl - , SO 4 2- , NO 3 - , HCO 3 - and PO 4 3- exhibited negligible effects on the degradation of SMX. Theoretical calculations corroborate that the distinctive spin-state reconstruction of Fe center in S-doped FeWO 4 is advantageous for H 2 O 2 decomposition. This discovery offers novel mechanistic insight into the enhanced catalytic activity of S doping in Fenton-like reactions and paves the way for expanding the application of FeWO 4 in wastewater treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Micro(nano)plastics widely detected in aquatic environments have caused serious threat to water quality security. However, as a potential important source of micro(nano)plastics in surface water during the COVID-19 pandemic, the ecological risks of face mask waste to aquatic environments remain poorly understood. Herein, we comprehensively characterized the micro(nano)plastics and organic compounds released from four daily used face masks in aqueous environments and further evaluated their potential impacts on aquatic ecosystem safety by quantitative genotoxicity assay. Results from spectroscopy and high-resolution mass spectrum showed that plastic microfibers/particles (∼11%-83%) and leachable organic compounds (∼15%-87%) were dominantly emitted pollutants, which were significantly higher than nanoplastics (< ∼5%) based on mass of carbon. Additionally, a toxicogenomics approach using green fluorescence protein-fused whole-cell array revealed that membrane stress was the primary response upon the exposure to micro(nano)plastics, whereas the emitted organic chemicals were mainly responsible for DNA damage involving most of the DNA repair pathways (e.g., base/nucleotide excision repair, mismatch repair, double-strand break repair), implying their severe threat to membrane structure and DNA replication of microorganisms. Therefore, the persistent release of discarded face masks derived pollutants might exacerbate water quality and even adversely affect aquatic microbial functions. These findings would contribute to unraveling the potential effects of face mask waste on aquatic ecosystem security and highlight the necessity for more developed management regulations in face mask disposal., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Although surface-enhanced Raman spectroscopy (SERS) offers a promising technology for sensitive detection of environmental pollutants in natural waters, its performance can be greatly affected by the environmental matrix. The lack of identification of the origin and the underlying mechanism of matrix effect hinders the application of SERS in practical environmental analysis. Herein, with silver nanoparticles (AgNPs) as a solution-based SERS substrate, the matrix effect from environmental waters on SERS analysis and the underlying mechanisms were investigated. It was found that natural water matrix could deteriorate SERS performance and cause artefacts in SERS spectra. Among various aqueous components, natural organic matter (NOM), including humic substances and proteins, mainly contributed to the matrix effect on SERS detection, while polysaccharides or inorganic ions had minor influence. The matrix effect from NOM was found to be prevalent for different analytes and SERS substrates. The mechanism of the matrix effect from NOM in the ternary system of analyte, NOM, and nanoparticles was investigated through three mutual interactions. The microheterogeneous repartition of analytes by NOM, other than the formation of NOM-corona or competitive adsorption between NOM and analytes on nanoparticles, was found to play the dominating role in interfering with SERS detection. This work illuminates the origin and underlying mechanisms of the matrix effect, which will promote the practical application of SERS technology in environmental analysis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

To date, eutrophication becomes a great concern of vulnerable aquatic systems. Dissolved organic phosphorus (DOP) discharged from wastewater treatment plant (WWTP) holds a large source of phosphorus in receiving water. However, due to the complexity of DOP, their variation and fate in WWTP remain unknown at the molecular level, and are always overlooked. Here, the variation of DOP in a WWTP was uncovered via Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Results show that 95% of DOP in the influent could be removed by the secondary biological treatment processes. The removed DOP species were mainly lipids with the molecular characteristics of low oxygen content, low unsaturation and low aromaticity. Meanwhile, during biological treatments, some new DOP species, especially lignin/carboxylic rich alicyclic molecules (CRAM) that possessed high oxygen content, high unsaturation and high aromaticity, were produced and released into the secondary effluent. In the subsequent tertiary treatment, coagulation by aluminum salt tended to remove high molecular weight and high oxygen content DOP species in the secondary effluent, which was complementary to the biological treatment. However, the sand filter usually retained microorganisms, which would result in the generation of new DOP species in this process. During the final ultraviolet disinfection process, DOP was effectively mineralized to phosphate, especially the species with high molecular weight and highly unsaturated aromatic DOP species (e.g., lignin/CRAM and tannin), which had higher UV absorbance. The revealed variation of DOP in WWTP is beneficial to optimize the treatment processes to enhance the removal of DOP., (Copyright © 2021. Published by Elsevier Ltd.)

Perfluorooctanoic acid (PFOA), an emerging and persistent pollutant, could cause toxicity effects on aquatic organisms. However, this was generally assessed under high exposure concentrations of PFOA and nutrient-enriched conditions, which was not accordant with the actual environments. Therefore, to comprehensively understand the toxicity effects of PFOA on aquatic organisms, the cellular responses of microalgae, Chlorella pyrenoidosa, to PFOA under different concentrations (≤ 1.0 mg/L) and nutrient conditions were investigated in this study. Results show that PFOA at concentrations less than 1.0 mg/L had no significant effects on algal growth and chlorophyll contents, and no oxidative damages were generated to destroy membrane integrity and morphology. However, N,P-limited and -starved conditions significantly decreased algal growth and chlorophyll contents, and induced oxidative stresses to ruin the structure and function of cell membrane. Moreover, the deficiency of P had more severe negative effect on algae than that of N, and they both influenced the toxicity responses of microalgae to 1.0 mg/L PFOA. The adsorption and uptake percentages of PFOA by algal cells were both less than 10%, and increased adsorption but decreased uptake of PFOA amounts occurred under N,P-limited and -starved conditions. These findings will be useful to understand the toxicity effects of PFOA on microalgae in aquatic environments., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Free DNA bases are widely present in the environments, and can be utilized by bacteria for their nucleic acids synthesis or as nutrition sources. In sunlit natural waters, these free bases probably undergo photodegradation which would change the bioavailable bases contents. Though the photodegradation of DNA has been investigated, the photodegradation behaviors of free bases may be quite different from those of DNA-confined bases in consideration of their different chemical environments. Herein, the photodegradation of four free bases (guanine, adenine, thymine and cytosine) was investigated. Results show that direct photodegradation of free bases in phosphate buffer caused by UV was slow. However, the photodegradation of these free bases were greatly enhanced in dissolved organic matter (DOM) solution. In the presence of 10-50 mg/L DOM, the photodegradation rates of free bases were increased by 1.85-14.6 times compared to the controls without DOM. DOM could result in indirect photodegradation by producing hydroxyl radical (•OH) and singlet oxygen ( 1 O 2 ) under irradiation, and this indirect photodegradation enhanced and dominated the free bases photodegradation. The •OH was involved in all four bases photodegradation, while the 1 O 2 only participated in guanine photodegradation. In phosphate buffer, the fastest photodegradation bases were pyrimidine, however, guanine became the fastest photodegradation base in DOM solution due to the selective oxidation of guanine by 1 O 2 . In summary, DOM may be a determinant for free bases photodegradation in natural waters and thereby deeply influence free bases fates in aquatic environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In nature, many microorganisms show resistance to toxic selenite by reducing selenite to non-soluble and low toxic elemental selenium. Extracellular polymeric substances (EPS), a high-molecular-weight biopolymers originated from microbial metabolism, contain many reducing groups and can induce reductive transformation of pollutants. However, the roles of EPS and its redox state in reductive detoxification or reduction removal of selenite, respectively, remain unknown yet. Herein, the reduction of selenite by different sources of EPS was investigated. Selenite was proved to be reduced by EPS and partly transformed to elemental selenium. The formed elemental selenium was mainly selenium nanoparticles confirmed by transmission electron microscopy coupled with energy dispersive spectroscopy. The redox state of EPS governed selenite reduction and elemental selenium formation, and the reduced state of EPS was in favor of selenite reduction. Dissolved oxygen concentration in water regulated EPS redox state and influenced selenite reduction. The thiols, aldehyde and phenolic groups in EPS were responsible for selenite reduction. Under selenite stress, EPS was capable of increasing cell survivability by enhancing microorganisms-mediated selenite reduction. This work revealed the previously undiscovered roles of EPS in selenite reduction and elemental selenium formation in aquatic environments and also suggested a possible crucial role of EPS in selenium biogeochemical cycle., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Three-dimensional electrochemical reactor (3DER) is a highly efficient technology for refractory wastewater treatment. Particle electrodes filled between anode and cathode are the core units of 3DER, determining the treatment efficiency of wastewater. However, particle electrodes deactivation due to catalytic sites coverage seriously impedes the continuous operation of 3DER. In this work, granular sludge carbon (GSC) particle electrodes being resistant to deactivation are fabricated by pyrolyzing the mixture of waste sludge, polymethyl methacrylate (PMMA), and copper tailings, whose performances are evaluated by degrading rhodamine B (RhB) wastewater in a continuous-flow 3DER. Results indicate that hierarchical-pore structure comprising macro-, meso-, and micropores is developed in GSC-10-CTs by doping 10 g PMMA and 5 g copper tailings into 100 g waste sludge. PMMA contributes to construct macropores, which is essential for the mass transfer of RhB into GSC particle electrodes of centimeter-size. Copper tailings promote the formation of meso- and micro-pores in GSCs, as well as improving the electrochemical properties. Consequently, GSC-10-CTs packed 3DER exhibits the highest removal efficiency and lowest energy consumption for RhB treatment. In addition, the compressive strength of GSC-10-CTs is enhanced by copper tails, that is crucial to fill into 3DER as particle electrodes. The high-efficient and cost-effective GSC-10-CTs fabricated by waste materials have the potential of substituting commercial granular activated carbon catalysts in the future, consequently promoting the application of 3DER in wastewater treatment., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Antibiotic resistance genes (ARGs) have been regarded as an emerging pollutant in municipal wastewater treatment plant (WWTP) effluents due to their potential risk to human health and ecological safety when reused for landscape and irrigation. Conventional wastewater treatment processes generally fail to effectively reduce ARGs, especially extracellular ARGs (eARGs), which are persistent in the environment and play an important role in horizontal gene transfer via transformation. Herein, an integrated process of pre-coagulation and microfiltration was developed for removal of ARGs, especially eARGs, from wastewater effluent. Results show that the integrated process could effectively reduce the absolute abundances of total ARGs (tARGs) (>2.9 logs) and eARGs (>5.2 logs) from the effluent. The excellent performance could be mainly attributed to the capture of antibiotic resistant bacteria (ARB) and eARGs by pre-coagulation and co-rejection during subsequent microfiltration. Moreover, the integrated process exhibited a good performance on removing common pollutants (e.g., dissolved organic carbon and phosphate) from the effluent to improve water quality. Besides, the integrated process also greatly reduced membrane fouling compared with microfiltration. These findings suggest that the integrated process of pre-coagulation and microfiltration is a promising advanced wastewater treatment technology for ARGs (especially eARGs) removal from WWTP effluents to ensure water reuse security., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The unique properties of ionic liquids make them attractive for a wide range of industrial applications, which makes it easy to be released into the environment and cause water or soil pollution. Phytoremediation of organic contaminants is a safe and important process for removing persistent pollutants from the environment. However, due to they are very chemically stable and potentially toxic to plants, whether they can be removed, assimilated and metabolized by plants remains unknown during phytoremediation process. In this study, ryegrass, Lolium perenne L., was used for imidazolium ionic liquid (1-butyl-3-methylimidazolium bromide, [C 4 mim] + ) removal from water. The results show that [C 4 mim] + could be taken up, accumulated and metabolized by plants in vivo with a high removal efficiency. Most of the [C 4 mim] + was accumulated in the root tissue, with the root concentration fraction factors ranging from 4.9 to 51.5. Two hydroxylated metabolites 1-(4-hydroxybutyl)-3-methylimidazolium, and 1-(n-butyl)-3-(hydroxymethyl)-imidazolium, and two secondary metabolites were detected in the ryegrass after [C 4 mim] + uptake. The metabolic mechanism was clarified using density functional theory calculations. Furthermore, [C 4 mim] + at a high concentration was found to be high toxic to inhibit the growth of ryegrass markedly. In response, some oxidative stress was observed in the metabolic process, as indicated by increasing of catalase, super dismutase and peroxidase activities. Our results suggested that phytoremediation was an efficient technique for ionic liquids treatment from water., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Coupling of anaerobic ammonium oxidation (anammox) and denitrifying anaerobic methane oxidation (DAMO) microorganisms in a hollow-fiber membrane biofilm reactor (HfMBR) is a potential strategy for simultaneous anaerobic removal of nitrogen and methane in wastewater streams. In these systems, effluents contain dissolved organic substances from anammox and DAMO microorganisms, but their characteristics and relationships have not been investigated. In the present study, excitation-emission matrix (EEM) fluorescence spectroscopy was used to characterize effluent dissolved organic matter (EfDOM) from an Anammox-DAMO HfMBR. Four component types (Component 1-4) were identified by parallel factor analysis (PARAFAC) of EEM data. Component 1 was produced when anammox and DAMO microorganisms simultaneously starved, whereas Component 4 was only generated through the starving period of DAMO microorganisms, and the longer the starving period, the higher the fluorescence intensity of the components. Components 2 and 3 were generated via active and starving periods of co-cultures. More efficient nitrogen removal was accompanied by a higher fluorescence intensity and microbial activity. Compared to measuring both influent and effluent nitrogen concentrations, monitoring EfDOM can obtain other information about the reactor, such as nitrogen removal activity of the reactor, status of the microbes and the duration of starving period the reactor suffered, which therefore offers a complementary but direct tool for assessing reactor performance in complex co-culture systems., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Antibiotic resistance genes (ARGs), as emerging environmental contaminants, have become a threat to human health. Recent studies have demonstrated that the effluent from wastewater treatment plants is a significant point source of ARGs released into the environment. In this study, we investigated the effectiveness of coagulation technology in the removal of ARGs from treated wastewater. Specifically, we measured the removal of five ARGs (two sulfonamide resistance genes, sulI and sulII, and three tetracycline resistance genes, tetO, tetW and tetQ) and the class 1 integron intI1 gene via the application of two coagulants: FeCl 3 and polyferric chloride (PFC). Moreover, the removal of dissolved organic carbon (DOC), NH 3 N and total phosphorus (TP) in the coagulation process was investigated. The coagulation process effectively removed ARGs from the effluent with 0.5-log to 3.1-log reductions. Significant removal correlations were observed between dissolved NH 3 N and DOC, intI1 and sulI, sulII and tetO, sulII and tetW, and tetO and tetW, implying that the co-removal of DOC, dissolved NH 3 N, the intI1 gene and different ARGs played an important role in ARG loss during coagulation with Fe-based coagulants. These results indicate that coagulation may play a promising role in ARG reduction in wastewater treatment plants., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Since nitrate causes severe ecological and health risks, nitrate contamination of drinking water sources has become one of the most important water quality concerns all over the world. Photocatalytic reduction of nitrate to molecular nitrogen presents a promising approach to remove nitrate from drinking water sources. However, harmful intermediates like NO 2 - , NO, NO 2 and N 2 O are usually formed, and metal loading or hole scavengers are generally needed to reduce the recombination of photo-generated electrons and holes, which will cause secondary pollution to drinking water. In this work, an efficient, selective and sustainable bioelectro-photocatalytic nitrate-reducing system by utilizing commercial TiO 2 nanoparticles P25 as the photocatalyst and bio-electrons from microbial metabolism as the hole scavenger is reported. In this system, bio-electrons extracted from organic substrates in bioanode are transferred to the photocathode through an external circuit for hole quenching. With the utilization of the residual photogenerated electrons, nitrate is completely reduced to nitrogen without accumulation of harmful nitrite or ammonium. The experimental results and the mechanistic analysis using the first-principles density functional theory calculations demonstrate that toxic by-products like nitrite or ammonium will not be accumulated in this system. Thus, this approach has a great potential for sustainable remediation of nitrate-contaminated drinking water sources., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Microbial extracellular polymeric substances (EPS) widely exist in natural environments and affect the migration and transformation of pollutants in aquatic environments. Previous works report that EPS have some reducing functional groups and can reduce heavy metals. However, because of the weak reducing capability of EPS, the reduction of heavy metals by EPS without cells is extremely slow, and its effect on heavy metals species is insignificant. In this work, the accelerated reduction of silver ions (Ag + ) by EPS from Shewanella oneidensis MR-1 under illumination was investigated. UV-visible spectroscopy, transmission electron microscopy (TEM) coupled with an energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were used to confirm the formation of silver nanoparticles (AgNPs) via the reduction of Ag + by EPS under light illumination. The Ag + reduction by EPS follows pseudo-first-order kinetics under both visible and UV light, and the light irradiation can significantly accelerate AgNPs formation. On the one hand, visible light can excite AgNPs for their surface plasma resonance (SPR) and accelerate the electrons from the EPS to adjacent Ag + . On the other hand, EPS molecules may be excited by UV light to produce strong reducing species, which enhance Ag + reduction. Moreover, pH, dissolved oxygen were found to affect the formation of AgNPs by EPS. This work proves the reducing capability of EPS on the reduction of Ag + , and this process can be accelerated under light illumination, which may affect the speciation and transformation of heavy metals in natural waters., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Soluble microbial products (SMP) formed by microorganisms in wastewater treatment plants (WWTPs) adversely affect final effluent quality and treatment efficiency. It is difficult to distinguish SMP from residual proteins, lipids and carbohydrates present in the influent that may persist during treatment. No method is currently available to determine quantitatively the extent to which SMP contribute to organic discharges from municipal WWTPs. In this work a modeling approach is presented which allows the SMP fraction of the effluent of a municipal WWTP to be quantified and described. The model is validated, in terms of utilization-associated products, biomass-associated products and extracellular polymeric substances, using influent from a municipal WWTP. SMP was found to account for, on average, 27 mg/L of chemical oxygen demand (COD), or 61% of the total COD in the WWTP effluent. Over 90% of the SMP was comprised of biomass-associated products. Five main factors influencing SMP formation in WWTP were evaluated. Neither wastewater composition nor mixed liquor suspended solids concentration was found to affect SMP production. On the other hand, a positive correlation was observed for SMP formation with both solids retention time and influent COD concentration, and a negative correlation with hydraulic retention time. Thus, operating or designing WWTPs with short solids retention and long hydraulic retention times could be considered as solutions for minimizing SMP production., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Enhanced biological phosphorus removal (EBPR) process is known to mainly rely on the ability of phosphorus-accumulating organisms to take up, transform and store excess amount of phosphorus (P) inside the cells. However, recent studies have revealed considerable accumulation of P also in the extracellular polymeric substances (EPS) of sludge, implying a non-negligible role of EPS in P removal by EBPR sludge. However, the contribution of EPS to P uptake and the forms of accumulated extracellular P vary substantially in different studies, and the underlying mechanism of P transformation and transportation in EPS remains poorly understood. This review provides a new recognition into the P removal process in EBPR system by incorporating the role of EPS. It overviews on the characteristics of P accumulation in EPS, explores the mechanism of P transformation and transportation in EBPR sludge and EPS, summarizes the main influential factors for the P-accumulation properties of EPS, and discusses the remaining knowledge gaps and needed future efforts that may lead to better understanding and use of such an EPS role for maximizing P recovery from wastewater., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Phosphorus accumulating organisms (PAOs) have been found to act as glycogen-accumulating organisms (GAOs) under certain conditions, thus, the deterioration in the performance of enhanced biological phosphorus removal systems is not always attributed to the proliferation of GAOs. In this work, the effects of calcium on the metabolic pathway of PAOs were explored. It was found that when the influent Ca(2+) concentration was elevated, the tendency and extent of extracellular calcium phosphate precipitation increased, and the intracellular inert Ca-bound polyphosphate was synthesized, while the microbial population remained almost unchanged. The changes in the ratios of phosphorus released/acetate uptaken, the glycogen degraded/acetate uptaken and the poly-β-hydroxyalkanoates synthesized/acetate uptaken during the anaerobic period confirm that, as the influent Ca(2+) concentration was increased, the polyphosphate-accumulating metabolism was partially shifted to the glycogen-accumulating metabolism. At an influent Ca(2+) around 50 mg/L, in addition to the extracellular calcium phosphate precipitation, the intracellular inert Ca-bound polyphosphate synthesis might also be involved in the metabolic change of PAOs. The results of the present work would be beneficial to better understand the biochemical metabolism of PAOs in enhanced biological phosphorus removal systems., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Zero-valent iron (ZVI) is increasingly being added into anaerobic reactors to enhance the biological conversion of various less biodegradable pollutants (LBPs). Our study aimed to establish a new structure model based on the Anaerobic Digestion Model No. 1 (ADM1) to simulate such a ZVI-based anaerobic reactor. Three new processes, i.e., electron release from ZVI corrosion, H2 formation from ZVI corrosion, and transformation of LBPs, were integrated into ADM1. The established model was calibrated and tested using the experimental data from one published study, and validated using the data from another work. A good relationship between the predicted and measured results indicates that the proposed model was appropriate to describe the performance of the ZVI-based anaerobic system. Our model could provide more precise strategies for the design, development, and application of anaerobic systems especially for treating various LBPs-containing wastewaters., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

How to mitigate membrane fouling remains a critical challenge for widespread application of membrane bioreactors. Herein, an antifouling electrochemical membrane bioreactor (EMBR) was developed based on in-situ utilization of the generated electricity for fouling control. In this system, a maximum power density of 1.43 W/m(3) and a current density of 18.49 A/m(3) were obtained. The results demonstrate that the formed electric field reduced the deposition of sludge on membrane surface by enhancing the electrostatic repulsive force between them. The produced H2O2 at the cathode also contributed to the fouling mitigation by in-situ removing the membrane foulants. In addition, 93.7% chemical oxygen demand (COD) removal and 96.5% NH4(+)-N removal in average as well as a low effluent turbidity of below 2 NTU were achieved, indicating a good wastewater treatment performance of the EMBR. This work provides a proof-of-concept study of an antifouling MBR with high wastewater treatment efficiency and electricity recovery, and implies that electrochemical control might provide another promising avenue to in-situ suppress the membrane fouling in MBRs., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The occurrences, transformation of antibiotics in biological wastewater treatment plants have attracted increasing interests. However, roles of extracellular polymeric substances (EPS) of activated sludge on the fate of antibiotics are not clear. In this study, the roles of EPS in the migration and removal of one typical antibiotic, sulfamethazine (SMZ), in activated sludge process were investigated. The interaction between EPS and SMZ was explored through a combined use of fluorescence spectral analysis, laser light scattering and microcalorimetry techniques. Results show that SMZ interacted with the proteins in EPS mainly with a binding constant of 1.91 × 10(5) L/mol. The binding process proceeded spontaneously, and the driving force was mainly from the hydrophobic interaction. After binding, the structure of EPS was expanded and became loose, which favored the mass transfer and pollution capture. The removal of SMZ was influenced by interaction with EPS. SMZ could be effectively adsorbed on EPS, which accounted for up to 61.8% of total SMZ adsorbed by sludge at the initial adsorption stage and declined to around 35.3% at the subsequent biodegradation stage. The enrichment of SMZ by EPS was beneficial for SMZ removal and acquisition by microbes at the subsequent biodegradation stage., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Metal binding to microbial extracellular polymeric substances (EPS) greatly influences the distribution of heavy metals in microbial aggregates, soil and aquatic systems in nature. In this work, the thermodynamic characteristics of the binding between aqueous metals (with copper ion as an example) and EPS of activated sludge were investigated. Isothermal titration calorimetry was employed to estimate the thermodynamic parameters for the binding of Cu²⁺ onto EPS, while three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis was used for quantifying the complexation of Cu²⁺ with the EPS. The binding mechanisms were further explored by X-ray absorption fine structure (XAFS) and Fourier transform infrared (FTIR) spectroscopy analysis. The results show that the proteins and humic substances in EPS were both strong ligands for Cu²⁺. The binding capacity N, binding constant K, binding enthalpy ΔH were calculated as 5.74 × 10⁻² mmol/g, 2.18 × 10⁵ L/mol, and -11.30 kJ/mol, respectively, implying that such a binding process was exothermic and thermodynamically favorable. The binding process was found to be driven mainly by the entropy change of the reaction. A further investigation shows that Cu²⁺ bound with the oxygen atom in the carboxyl groups in the EPS molecules of activated sludge. This study facilitates a better understanding about the roles of EPS in protecting microbes against heavy metals., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Soluble microbial products (SMP) generated by microbial populations can adversely affect the efficiency of biological wastewater treatment systems and secondary effluent quality. In this work, both experimental and modeling approaches were used to investigate the formation of SMP by both heterotrophic and autotrophic bacteria. Strategies to control and reduce SMP in activated sludge systems were thus evaluated. SMP produced by heterotrophs were found to account for more than 92% of total SMP. The SMP produced by autotrophs contributed to less than 8% of the total SMP, with 5% attributable to the ammonia-oxidizing bacteria (AOB) and 3% to the nitrite-oxidizing bacteria (NOB). When external organic substrate was present, the utilization-associated products (UAP) were the main component of SMP. When external organic substrate was completely consumed, biomass-associated products (BAP) from the hydrolysis of extracellular polymeric substances (EPS) dominated the SMP. The model developed in this study described the fractions and dynamics of UAP and BAP produced by heterotrophs, AOB and NOB. Solids retention time of the reactor had a significant effect on SMP production, while the effect of the hydraulic retention time was only minor. Decreasing the solids retention time from 15 to 0.5 d reduced SMP production in the reactor by 62%., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The electro-Fenton process is efficient for degradation of organic pollutants, but it suffers from the high operating costs due to the need of power investment. Here, a new anodic Fenton system is developed for energy-saving and efficient treatment of organic pollutants by incorporating microbial fuel cell (MFC) into an anodic Fenton process. This system is composed of an anodic Fenton reactor and a two-chamber air-cathode MFC. The power generated from a two-chamber MFC is used to drive the anodic Fenton process for Acid Orange 7 (AO7) degradation through accelerating in situ generation of Fe(2+) from sacrificial iron. The kinetic results show that the MFC-assisted anodic Fenton process system had a significantly higher pseudo-first-order rate constant than those for the chemical Fenton methods. The electrochemical analysis reveals that AO7 did not hinder the corrosion of iron. The anodic Fenton process was influenced by the MFC performance. It was also found that increasing dissolved oxygen in the cathode improved the MFC power density, which in turn enhanced the AO7 degradation rate. These clearly demonstrate that the anodic Fenton process could be integrated with MFC to develop a self-sustained system for cost-effective and energy-saving electrochemical wastewater treatment., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Configuration of extracellular polymeric substances (EPS) excreted by microorganisms is related greatly to the inherent properties of EPS, and has a significant effect on the physicochemical characteristics of microbial aggregates, such as activated sludge for wastewater treatment, as well as their interaction with other substances in aqueous systems. In this work, the spatial configuration of microbial EPS is characterized using laser light scattering (LLS) technique, with EPS extracted from Bacillus megaterium TF10 as an example. The combined utilization of static light scanning (SLS) and dynamic light scanning (DLS) offers an effective avenue to explore the EPS configuration in aqueous solution, thus enables a better understanding about the physicochemical properties of EPS. The results show that EPS exist in the form of colloids in neutral aqueous solution (pH 7.0) and that their shape is random coil with incompletely extending chains. The attraction interaction between EPS colloids is related with the high flocculability of B. megaterium TF10. The cryo-electron microscopy image further confirms the spherical shape of EPS colloids. The LLS approach offers a powerful and convenient tool for characterizing microbial EPS configuration and understanding their behaviors in biological wastewater treatment systems., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The fouling characteristics of proton exchange membrane (PEM) in microbial fuel cell (MFC) and the resulting deterioration of MFC performance were explored in this study. It was observed that the ion exchange capacity, conductivity and diffusion coefficients of cations of PEM were reduced significantly after fouling. Imaging analysis coupled with FTIR analysis indicated that the fouling layer attached on PEM consisted of microorganisms encased in extracellular polymers and inorganic salt precipitations. The results clearly demonstrate that PEM fouling deteriorated the performance of MFCs and led to a decrease in electricity generation. Cation transfer limitation might play an important role in the deterioration of MFC performance because of the membrane fouling. This was attributed to the physical blockage of charge transfer in the MFC resulted from the membrane fouling. With the experimental results, the effect of membrane fouling on the electrical generation of MFCs was evaluated. It was found that the decreased diffusion coefficients of cations and cathodic potential loss after membrane fouling contributed mainly to the deterioration of the MFC performance., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Soluble microbial products (SMPs) present a major part of residual chemical oxygen demand (COD) in the effluents from biological wastewater treatment systems, and the SMP formation is greatly influenced by a variety of process parameters. In this study, response surface methodology (RSM) coupled with grey relational analysis (GRA) method was used to evaluate the effects of substrate concentration, temperature, NH(4)(+)-N concentration and aeration rate on the SMP production in batch activated sludge reactors. Carbohydrates were found to be the major component of SMP, and the influential priorities of these factors were: temperature>substrate concentration > aeration rate > NH(4)(+)-N concentration. On the basis of the RSM results, the interactive effects of these factors on the SMP formation were evaluated, and the optimal operating conditions for a minimum SMP production in such a batch activated sludge system also were identified. These results provide useful information about how to control the SMP formation of activated sludge and ensure the bioreactor high-quality effluent., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Microbial fuel cells (MFCs) provide new opportunities for the simultaneous wastewater treatment and electricity generation. Enhanced oxygen reduction capacity of cost-effective metal-based catalysts in an air cathode is essential for the scale-up and commercialization of MFCs in the field of wastewater treatment. We demonstrated that a nano-structured MnO(x) material, prepared by an electrochemically deposition method, could be an effective catalyst for oxygen reduction in an MFC to generate electricity with the maximum power density of 772.8 mW/m(3) and remove organics when the MFC was fed with an acetate-laden synthetic wastewater. The nano-structured MnO(x) with the controllable size and morphology could be readily obtained with the electrochemical deposition method. Both morphology and manganese oxidation state of the nano-scale catalyst were largely dependent on the electrochemical preparation process, and they governed its catalytic activity and the cathodic oxygen reduction performance of the MFC accordingly. Furthermore, cyclic voltammetry (CV) performed on each nano-structured material suggests that the MnO(x) nanorods had an electrochemical activity towards oxygen reduction reaction via a four-electron pathway in a neutral pH solution. This work provides useful information on the facile preparation of cost-effective cathodic catalysts in a controllable way for the single-chamber air-cathode MFC for wastewater treatment., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

An integrated approach incorporating response surface methodology, grey relational entropy, and fuzzy analytic hierarchy process is established to prioritize the influence of main factors governing the anaerobic H(2) production process and their influential priority. Response surface methodology is employed to design experiments, and the grey relational entropy is used to evaluate the influential grade of the three input factors, i.e., pH, temperature and initial substrate concentration (S(ini)), on the H(2) yield, maximum H(2) production rate and volatile fatty acid yield. In addition, through a combination of grey relational entropy, fuzzy analytic hierarchy process, which is used to determine the weight, and accelerating genetic algorithm, which is employed to minimize the nonlinear function in fuzzy analytic hierarchy process, the overall H(2) production process performance could be comprehensively evaluated. The results show that pH is the most important factor influencing the yields of H(2) and volatile fatty acids, while S(ini) has the most significant effect on the maximum H(2) production rate. Compared to pH and S(ini), temperature has a less important effect on the overall H(2) production reactor performance. This approach provides an appropriate way to identify the influential priority of input factors and to evaluate the overall performance for the anaerobic H(2) production process, and it can also be used for other complex biological and non-biological wastewater treatment systems.

Soluble microbial products (SMP) are the pool of organic compounds originating from microbial growth and decay, and are usually the major component of the soluble organic matters in effluents from biological treatment processes. In this work, SMP in activated sludge were characterized, fractionized, and quantified using integrated chemical analysis and mathematical approach. The utilization-associated products (UAP) in SMP, produced in the substrate-utilization process, were found to be carbonaceous compounds with a molecular weight (MW) lower than 290 kDa which were quantified separately from biomass-associated products (BAP). The BAP were mainly cellular macromolecules with an MW in a range of 290-5000 kDa, and for the first time were further classified into the growth-associated BAP (GBAP) with an MW of 1000 kDa, which were produced in the microbial growth phase, and the endogeny-associated BAP (EBAP) with an MW of 4500 kDa, which were generated in the endogenous phase. Experimental and modeling results reveal that the UAP could be utilized by the activated sludge and that the BAP would accumulate in the system. The GBAP and EBAP had different formation rates from the hydrolysis of extracellular polymeric substances and distinct biodegradation kinetics. This study provides better understanding of SMP formation mechanisms and becomes useful for subsequent effluent treatment., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

A near-infrared-reflectance (NIR) spectroscopy-based method is established to determine the main components of aquatic plants as well as their anaerobic rumen biodegradability. The developed method is more rapid and accurate compared to the conventional chemical analysis and biodegradability tests. Moisture, volatile solid, Klason lignin and ash in entire aquatic plants could be accurately predicted using this method with coefficient of determination (r(2)) values of 0.952, 0.916, 0.939 and 0.950, respectively. In addition, the anaerobic rumen biodegradability of aquatic plants, represented as biogas and methane yields, could also be predicted well. The algorithm of continuous wavelet transform for the NIR spectral data pretreatment is able to greatly enhance the robustness and predictive ability of the NIR spectral analysis. These results indicate that NIR spectroscopy could be used to predict the main components of aquatic plants and their anaerobic biodegradability., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

In this work, pulp mill wastewater was treated using a novel copolymer flocculant with a high water-solubility, which was synthesized through grafting (2-methacryloyloxyethyl) trimethyl ammonium chloride (DMC) onto chitosan initiated by potassium persulphate. The experimental results demonstrate that the two main problems associated with the utilization of chitosan as a flocculant, i.e., low molecular weight and low water-solubility, were concurrently sorted out. The physicochemical properties of this flocculant were characterized with Fourier-transform infrared spectroscopy, (1)H nuclear magnetic resonance spectroscopy, X-ray powder diffraction and field emission scanning electron microscopy. Reaction parameters influencing the grafting percentage, such as temperature, reaction time, initiator concentration and monomer concentration, were optimized using an orthogonal array design matrix. With an increase in grafting percentage, the water-solubility of the flocculant was improved, and it became thoroughly soluble in water when the grafting percentage reached 236.4% or higher. Its application for the treatment of pulp mill wastewater indicates that it had an excellent flocculation capacity and that its flocculation efficiency was much better than that of polyacrylamide. The optimal conditions for the flocculation treatment of pulp mill wastewater were also obtained.

A rapid quantification method, based on Fourier transform near-infrared (FT-NIR) spectroscopy, was developed and validated to nondestructively quantify the concentrations of volatile fatty acids and ethanol in the effluent of an anaerobic H(2)-producing bioreactor. The first-derivative spectra calculated by a simple numerical difference, combined with the orthogonal signal correction method, were used as spectral preprocessing options. A calibration model was established and validated using gas chromatography measurement results. The number of internal latent variables was optimized based on the lowest root-mean-square error of calibration. The calibration model established shows the satisfactory results for the lowest root-mean-square errors of prediction compared to other preprocess methods. The method developed in this work is demonstrated to be more flexible compared with other approaches to determine the concentrations of volatile fatty acids and ethanol in the anaerobic reactor effluents.

Ipomoea aquatica with low-energy N+ ion implantation was used for the removal of both nitrogen and phosphorus from the eutrophic Chaohu Lake, China. The biomass growth, nitrate reductase and peroxidase activities of the implanted I. aquatica were found to be higher than those of I. aquatica without ion implantation. Higher NO3-N and PO4-P removal efficiencies were obtained for the I. aquatica irradiation at 25 keV, 3.9 x 10(16) N+ ions/cm(2) and 20 keV 5.2 x 10(16) N+ ions/cm(2), respectively (p < 0.05). Moreover, the nitrogen and phosphorus contents in the plant biomass with ion implantation were also greater than those of the controls. I. aquatica with ion implantation was directly responsible for 51-68% N removal and 54-71% P removal in the three experiments. The results further confirm that the ion implantation could enhance the growth potential of I. aquatica in real eutrophic water and increase its nutrient removal efficiency. Thus, the low-energy ion implantation for aquatic plants could be considered as an approach for in situ phytoremediation and bioremediation of eutrophic waters.

In this work the extracellular polymeric substances (EPS) produced by mixed microbial community in activated sludge are characterized using gel-permeating chromatography (GPC), 3-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy measurement and mathematical modeling. Chromatograms of extracted EPS exhibit seven peaks, among which proteins have four peaks and polysaccharides have three peaks. Evolution of the chromatogram area indicates that the quantity of produced EPS increases significantly in the substrate utilization process. With the parallel factor analysis (PARAFAC) approach, two components of the polymer matrix are identified by the EEM analysis, one as EPS proteins at Ex/Em 280/340 nm and one matrix associated as fulvic-acid-like substances at 320/400 nm. The proteins and fulvic-acid-like substances in the EPS increase in the substrate utilization phase, but decrease in the endogenous phase. To have a better insight into EPS production, the kinetic modeling of EPS is performed with regard to their molecular weight distribution and chemical natures identified by GPC and EEM. In this way, the dynamics of these important microbial products are better understood.

Calcium-rich aerobic granules were cultivated after 3-month operation. The chemical form and spatial distribution of calcium in the granules and their physicochemical characteristics were explored. Examination with a scanning electron microscope combined energy dispersive X-ray detector (SEM-EDX) shows that Ca was mainly accumulated in the core of the granules. CaCO(3) was found to be the main calcium precipitate in the granules. The fluorescent in situ hybridization (FISH) analysis shows that the cells were crowded in the outer layer and gathered in clusters. Compared with the granules without Ca accumulation, the Ca-rich granules had more rigid structure and a higher strength. However, their specific oxygen uptake rate (SOUR) reduced after the Ca accumulation inside them. Comparison between the SOUR values of the granules with and without Ca accumulation suggests that Ca accumulated in the aerobic granules might have a negative effect on their bioactivity.

A simple and sensitive method was developed for the determination of low-concentration proteins and carbohydrates in the effluents from biological wastewater treatment reactors using resonance light-scattering (RLS) technique. Two ionic dyes, Congo red and Neutral red were, respectively used as an RLS probes for the determination of proteins and carbohydrates. This method is based on the interactions between biomacromolecules and dyes, which cause a substantial increase in the resonance scattering signal of dyes in the wavelength range of 200-650 nm. The characteristics of RLS spectra of the macromolecule-dye complexes, influencing factors, and optimum analytical conditions for the measurement were explored. The method was satisfactorily applied to the measurement of proteins and carbohydrates in the effluents from 10 aerobic or anaerobic bioreactors, and a high sensitivity were achieved.

Three-dimensional excitation-emission-matrix (EEM) fluorescence spectrometry was used to characterize the extracellular and intracellular substances of activated sludge in a sequencing batch reactor (SBR). Parallel factor analysis (PARAFAC) was applied to extract the pure spectra from the overlapped spectra. Three main components, proteins, fulvic- and humic-like substances, were identified from the extracellular substances. Their fluorescence peaks were at an excitation/emission (Ex/Em) of 280/350, 340/400 and 390/450 nm, respectively. The fluorescence of the extracellular proteins had a similar changing pattern with the wastewater chemical oxygen demand, the fulvic-like substance did not vary significantly in a cycle and the humic-like substances accumulated in the substrate uptake phase but decreased later. Proteins and nicotinamide adenine dinucleotide, reduced form (NADH), were identified as the two main intracellular fluorophores, and their fluorescence peaks (Ex/Em) were at 280/340 and 350/450 nm, respectively. The fluorescence intensity scores of the intracellular fluorophores were closely related to the bioreactor performance. Thus, the results of this work provide a foundation for potential utilization of the EEM fluorescence spectroscopy to monitor the activated sludge systems for wastewater treatment.

The aim of this study was to investigate the use of water spinach (Ipomoea aquatica Forsk.) with N(+) ion-beam implantation for removal of nutrient species from eutrophic water. The mutated water spinach was grown on floating beds, and growth chambers were used to examine the growth of three cultivars of water spinach with ion implantation for 14 days in simulated eutrophic water at both high and low nitrogen levels. The specific weight growth rates of three cultivars of water spinach with ion implantation were significantly higher than the control, and their NO(3)-N and NH(4)-N removal efficiencies were also greater than those of the control. Furthermore, compared with the control, the nitrogen contents in the plant biomass with ion implantation were higher as well.

In this study three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy was applied to characterize the extracellular polymeric substances (EPS) extracted from aerobic and anaerobic sludge in wastewater treatment. Three fluorescence peaks were identified in EEM fluorescence spectra of the EPS samples. Two peaks were attributed to the protein-like fluorophores, and the third to the humic-like fluorophores. The effects of both pH and EPS concentration were significant on EEM fluorescence spectra of EPS, but the ionic strength had no substantial effect on EEM spectra of the EPS. The differences in the EPS fluorescence parameters, e.g., peak locations, intensities and ratios of various peak intensities, indicate the difference in the chemical structures of the EPS from various origins. EEM spectroscopy was proven to be an appropriate and effective method to characterize the EPS from various origins in wastewater treatment systems.