Impact of hydrogen sulfide on anammox and nitrate/nitrite-dependent anaerobic methane oxidation coupled technologies.

The coupling between anammox and nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) has been considered a sustainable technology for nitrogen removal from sidestream wastewater and can be implemented in both membrane biofilm reactor (MBfR) and granular bioreactor. However, the potential influence of the accompanying hydrogen sulfide (H2S) in the anaerobic digestion (AD)-related methane-containing mixture on anammox/n-DAMO remains unknown. To fill this gap, this work first constructed a model incorporating the C/N/S-related bioprocesses and evaluated/calibrated/validated the model using experimental data. The model was then used to explore the impact of H2S on the MBfR and granular bioreactor designed to perform anammox/n-DAMO at practical levels (i.e., 0∼5% (v/v) and 0∼40 g/S m3, respectively). The simulation results indicated that H2S in inflow gas did not significantly affect the total nitrogen (TN) removal of the MBfR under all operational conditions studied in this work, thus lifting the concern about applying AD-produced biogas to power up anammox/n-DAMO in the MBfR. However, the presence of H2S in the influent would either compromise the treatment performance of the granular bioreactor at a relatively high influent NH4+-N/NO2--N ratio (e.g., >1.0) or lead to increased energy demand associated with TN removal at a relatively low influent NH4+-N/NO2--N ratio (e.g., <0.7). Such a negative effect of the influent H2S could not be attenuated by regulating the hydraulic residence time and should therefore be avoided when applying the granular bioreactor to perform anammox/n-DAMO in practice.

Degradation of Chloroquine by Ammonia-Oxidizing Bacteria: Performance, Mechanisms, and Associated Impact on N2O Production.

Since the mass production and extensive use of chloroquine (CLQ) would lead to its inevitable discharge, wastewater treatment plants (WWTPs) might play a key role in the management of CLQ. Despite the reported functional versatility of ammonia-oxidizing bacteria (AOB) that mediate the first step for biological nitrogen removal at WWTP (i.e., partial nitrification), their potential capability to degrade CLQ remains to be discovered. Therefore, with the enriched partial nitrification sludge, a series of dedicated batch tests were performed in this study to verify the performance and mechanisms of CLQ biodegradation under the ammonium conditions of mainstream wastewater. The results showed that AOB could degrade CLQ in the presence of ammonium oxidation activity, but the capability was limited by the amount of partial nitrification sludge (∼1.1 mg/L at a mixed liquor volatile suspended solids concentration of 200 mg/L). CLQ and its biodegradation products were found to have no significant effect on the ammonium oxidation activity of AOB while the latter would promote N2O production through the AOB denitrification pathway, especially at relatively low DO levels (≤0.5 mg-O2/L). This study provided valuable insights into a more comprehensive assessment of the fate of CLQ in the context of wastewater treatment.

Competitive enrichment of comammox Nitrospira in floccular sludge.

The discovery of complete ammonium oxidation (comammox) has subverted the traditional perception of two-step nitrification, which plays a key role in achieving biological nitrogen removal from wastewater. Floccular sludge-based treatment technologies are being applied at the majority of wastewater treatment plants in service where detection of various abundances and activities of comammox bacteria have been reported. However, limited efforts have been made to enrich and subsequently characterize comammox bacteria in floccular sludge. To this end, a lab-scale sequencing batch reactor (SBR) in the step-feeding mode was applied in this work to enrich comammox bacteria through controlling appropriate operational conditions (dissolved oxygen of 0.5 ± 0.1 g-O2/m3, influent ammonium of 40 g-N/m3 and uncontrolled longer sludge retention time). After 215-d operation, comammox bacteria gradually gained competitive advantages over counterparts in the SBR with a stable nitrification efficiency of 92.2 ± 2.2 %: the relative abundance of Nitrospira reached 42.9 ± 1.3 %, which was 13 times higher than that of Nitrosomonas, and the amoA gene level of comammox bacteria increased to 7.7 ± 2.1 × 106 copies/g-biomass, nearly 50 times higher than that of conventional ammonium-oxidizing bacteria. The enrichment of comammox bacteria, especially Clade A Candidatus Nitrospira nitrosa, in the floccular sludge led to (i) apparent affinity constants for ammonium and oxygen of 3.296 ± 0.989 g-N/m3 and 0.110 ± 0.004 g-O2/m3, respectively, and (ii) significantly low N2O and NO production, with emission factors being 0.136 ± 0.026 % and 0.023 ± 0.013 %, respectively.

Structure and function of microbiomes in the rhizosphere and endosphere response to temperature and precipitation variation in Inner Mongolia steppes.

Introduction: Owing to challenges in the study of complex rhizosphere and endophytic microbial communities, the composition and function of such microbial communities in steppe ecosystems remain elusive. Here, we studied the microbial communities of the rhizosphere and endophytic microbes of the dominant plant species across the Inner Mongolian steppes using metagenomic sequencing and investigated their relationships with changes in mean annual temperature (MAT) and mean annual precipitation (MAP). Methods: Metagenomic sequencing based on Illumina high-throughput sequencing, using the paired end method to construct a small fragment library for sequencing. Results: Adaptation of root systems to the environment affected the composition and function of rhizosphere and endophytic microbial communities. However, these communities exhibited distinct community assembly and environmental adaptation patterns. Both rhizosphere and endophytic microbial communities can be divided into two unrelated systems based on their ecological niches. The composition and function of the rhizosphere microbial communities were mainly influenced by MAT, while those of the endophytic microbial communities were mainly influenced by MAP. MAT affected the growth, reproduction, and lipid decomposition of rhizosphere microorganisms, whereas MAP affected reverse transcription and cell wall/membrane/envelope biogenic functions of endophytic microorganisms. Conclusion: Our findings reveal the composition and function of the rhizosphere and endophytic microbial communities in response to changes in MAP and MAT, which has important implications for future biogeography and climate change research.

Facile synthesis of spherical covalent organic frameworks for enrichment and quantification of aryl organophosphate esters in mouse serum and tissues.

Here, an imine-linked-based spherical covalent organic framework (COF) was prepared at room temperature. The as-synthesized spherical COF served as an adsorbent in dispersive solid-phase extraction (dSPE), by its virtue of great surface area (1542.68 m2 /g), regular distribution of pore size (2.95 nm), and excellent stability. Therefore, a simple and high-efficiency dispersive solid phase extraction method based on a spherical COF coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established to determine aryl organophosphate esters in biological samples. This approach displayed favorable linearity in the range of 10.0-1000.0 ng/L (r > 0.9989), a high signal enhancement factor (58.8-181.8 folds) with low limits of detection (0.3-3.3 ng/L). Moreover, it could effectively eliminate complex matrix interference to accurately extract seven aryl organophosphate esters from mouse serum and tissue samples with spiked recoveries of 82.0%-117.4%. The as-synthesized spherical COF has been successfully applied in sample preparation. The dSPE-HPLC-MS/MS method based on a spherical COF has potential application to study the pollutants' metabolism in vivo.

Graphene Enhances the Loading Capacity and Lubrication Performance of Ionic Liquids: A Molecular Dynamics Study.

Ionic liquid (IL) combined with graphene additives have garnered extensive attention in the field of high-performance lubricating materials. However, the ambiguous mechanism of graphene influencing the load-carrying and anti-wear capacity of ILs needs further study. In this work, friction simulation shows that adding graphene causes friction coefficient to reduce by up to 88% compared with pure ILs, but lubrication performance is lost due to the destruction of graphene under high stress. Meanwhile, multilayer graphene has better friction-reducing performance and friction durability as compared to the monolayer structure, which is attributed to the easy-shear property and the reduction in the percentage of high tensile stress sites in multilayer graphene structure. In addition, it was found that excessively thick ILs film would form a three-body abrasive wear structure with graphene, which accelerated the structural destruction of graphene and caused a decline in its tribological properties. It is believed these findings can be valuable for designing of high-performance lubricating oil for practical engineering.

Impacts of granular sludge properties on the bioreactor performing nitrate/nitrite-dependent anaerobic methane oxidation/anammox processes.

In this work, a bioprocess model was applied to first determine the impacts of influent substrates conditions on the granular bioreactor performing nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) and anammox integrated processes and then investigate the roles of granular sludge properties in regulating the bioreactor performance and start-up process. The ideal influent substrates conditions were identified at NO2--N/NH4+-N of 1:1 and dissolved CH4 concentration of 85 g COD m-3, which achieved 98.6% total nitrogen removal and 87.7% dissolved CH4 utilization. Under such ideal influent conditions, the initial properties of granular sludge didn't significantly affect the granular bioreactor performance. However, inoculation of granular sludge with a relatively small granular sludge size and a high abundance of n-DAMO archaea or/and anammox bacteria could effectively shorten the bioreactor start-up. Meanwhile, reducing the diffusivity of solutes within granular sludge was also beneficial for expediting the start-up process and promoting dissolved CH4 utilization.

Model-based development of strategies enabling effective enrichment and application of comammox bacteria in floccular sludge under mainstream conditions.

The discovery of complete ammonium oxidation (comammox) has redefined the perception of the nitrification process which plays a vital part in biological nitrogen removal (BNR) from wastewater. Despite the reported detection or cultivation of comammox bacteria in biofilm or granular sludge reactors, limited attempts have been made to enrich or assess comammox bacteria in floccular sludge reactors with suspended growth of microbes, which are most extensively applied at wastewater treatment plants. Therefore, through making use of a comammox-inclusive bioprocess model reliably evaluated using batch experimental data with joint contributions of different nitrifying guilds, this work probed into the proliferation and functioning of comammox bacteria in two commonly-used floccular sludge reactor configurations, i.e., continuous stirred tank reactor (CSTR) and sequencing batch reactor (SBR), under mainstream conditions. The results indicated that compared with the studied SBR, the CSTR was observed to favor the enrichment of comammox bacteria through maintaining a sufficient sludge retention time (40-100 d) while avoiding an extremely low DO level (e.g., 0.05 g-O2/m3), irrespective of the varied influent NH4+-N of 10-100 g-N/m3. Meanwhile, the inoculum sludge was found to greatly influence the start-up process of the studied CSTR. By inoculating the CSTR with a sufficient amount of sludge, finally enriched floccular sludge with a high abundance of comammox bacteria (up to 70.5 %) could be rapidly obtained. These results not only benefitted further investigation and application of comammox-inclusive sustainable BNR technologies but also explained, to some extent, the discrepancy in the reported presence and abundance of comammox bacteria at wastewater treatment plants adopting floccular sludge-based BNR technologies.

Towards efficient heterotrophic recovery of N2O via Fe(II)EDTA-NO: A modeling study.

Efficient recovery of nitrous oxide (N2O) through heterotrophic denitrification with the help of Fe(II)EDTA-NO as a chelating agent has been regarded as an ideal technology to treat nitric oxide (NO)-rich flue gas. In this study, an integrated NO-based biological denitrification model was developed to describe the sequential reduction of the NO fixed in Fe(II)EDTA-NO with organic carbon as the electron donor. With the inclusion of only the key pathways contributing to nitrogen transformation, the model was firstly developed and then calibrated/validated and evaluated using the data of batch tests mediated by the identified functional heterotrophic bacteria at various substrates concentrations and then used to explore the possibility of enhancing N2O recovery by altering the substrates condition and reactor setup. The results demonstrated that the optimal COD/N ratio decreased consistently from 1.5 g-COD/g-N at the initial NO concentration of 40 g-N/m3 to 1.0 g-COD/g-N at the initial NO concentration of 420 g-N/m3. Furthermore, sufficiently increasing the headspace volume of the reactor was considered an ideal strategy to obtain ideal N2O production of 86.6 % under the studied conditions. The production of high-purity N2O (98 %) confirmed the practical application potential of this integrated treatment technology to recover a valuable energy resource from NO-rich flue gas.

Instrumental role of bioreactors in nitrate/nitrite-dependent anaerobic methane oxidation-based biotechnologies for wastewater treatment: A review.

Recently, the nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) processes have become a research hotspot in the field of wastewater treatment. The n-DAMO processes could not only mitigate direct and indirect carbon emissions from wastewater treatment plants but also strengthen biological nitrogen removal. However, the applications of n-DAMO-based biotechnologies face practical difficulties mainly caused by the distinctive properties of n-DAMO microorganisms and the limited/availability of methane with poor solubility. In this sense, the choice of bioreactors will play important roles that influence the growth and functioning of n-DAMO microorganisms, thus enabling dedicated development of the n-DAMO processes and efficient applications of n-DAMO-based biotechnologies. Therefore, this paper aims to discuss the three commonly-applied types of bioreactors, covering the individual working principle and state-of-the-art removal performance of nitrogen as well as dissolved methane observed when adopted for n-DAMO-based biotechnologies. With noted limitations for each bioreactor type, several key perspectives were proposed which hopefully would inspire future investigation and practical applications of the n-DAMO processes.

The effect of nitrification inhibitors on the aerobic biodegradation of tetracycline antibiotics in swine wastewater.

The aerobic biotreatment process for the dual goals of antibiotic removal and ammonia retainment for the field-return-based treatment of swine wastewater was optimized by adding 2-chloro-6-trichloromethylpyridine (TCMP), commonly used as a nitrogen fertilizer synergist. The results show that the dosage of 5-10 mg/L TCMP daily effectively inhibited nitrification. The COD and tetracycline antibiotics (TCs) in the absence of TCMP was removed by 91% and 76%, and became 87% and 78% with 5 mg/L TCMP and 83% and 70% with 10 mg/L TCMP, respectively. The removal efficiency of four TCs generally followed a decreasing trend of chlortetracycline (CTC) > doxycycline (DC) > tetracycline (TC) > oxytetracycline (OTC). A dosage of 5 mg/L TCMP daily inhibited ammonia nitrification effectively and only slightly affected the removal of conventional organic pollutants and TCs. The contribution of volatilization and hydrolysis to the removal of TCs was negligible. The overall removal efficiency of four TCs in removal pathway experiments was 98%, 94%, 97%, and 96% for OTC, CTC, DC, and TC, of which 69%, 41%, 56%, and 62% was contributed by absorption, and 29%, 53%, 41%, and 34% was contributed by biodegradation, respectively. This study may have significant implications for the proper management of livestock wastewater intended to be used as fertilizers, which aims to reduce the exposure risk of antibiotics and preserve its nutrient value.

Influences of longitudinal gradients on methane-driven membrane biofilm reactor for complete nitrogen removal: A model-based investigation.

Integrating anammox with denitrifying anaerobic methane oxidation (DAMO) in the membrane biofilm reactor (MBfR) is a promising technology capable of achieving complete nitrogen removal from wastewater. However, it remains unknown whether reactor configurations featuring longitudinal gradients parallel to the membrane surface would affect the performance of the CH4-driven MBfR. To this end, this work aims to study the impacts of longitudinal heterogeneity potentially present in the gas and liquid phases on a representative CH4-driven MBfR performing anammox/DAMO by applying the reported modified compartmental modeling approach. Through comparing the modeling results of different reactor configurations, this work not only offered important guidance for better design, operation and monitoring of the CH4-driven MBfR, but also revealed important implications for prospective related modeling research. The total nitrogen removal efficiency of the MBfR at non-excessive CH4 supply (e.g., surface loading of ≤0.064 g-COD m-2 d-1 in this work) was found to be insensitive to both longitudinal gradients in the liquid and gas phases. Comparatively, the longitudinal gradient in the liquid phase led to distinct longitudinal biomass stratification and therefore played an influential role in the effective CH4 utilization efficiency, which was also related to the extent of reactor compartmentation considered in modeling. When supplied with non-excessive CH4, the MBfR is recommended to be designed/operated with both the biofilm reactor and the membrane lumen as plug flow reactors (PFRs) with co-current flow of wastewater and CH4, which could mitigate dissolved CH4 discharge in the effluent. For the reactor configurations with the biofilm reactor designed/operated as a PFR, multi-spot sampling in the longitudinal direction is needed to obtain a correct representation of the microbial composition of the MBfR.

A comprehensive analysis of evolution and underlying connections of water research themes in the 21st century.

This work aimed to reflect the advancements in water-related science, technology, and policy and shed light on future research opportunities related to water through a systematic overview of Water Research articles published in the first 21.5 years of the 21st century. Specific bibliometric analyses were performed to i) reveal the temporal and spatial trends of water-related research themes and ii) identify the underlying connections between research topics. The results showed that while top topics including wastewater (treatment), drinking water, adsorption, model, biofilm, and bioremediation remained constantly researched, there were clear shifts in topics over the years, leading to the identification of trending-up and emerging research topics. Compared to the first decade of the 21st century, the second decade not only experienced significant uptrends of disinfection by-products, anaerobic digestion, membrane bioreactor, advanced oxidation processes, and pharmaceuticals but also witnessed the emerging popularity of PFAS, anammox, micropollutants, emerging contaminants, desalination, waste activated sludge, microbial community, forward osmosis, antibiotic resistance genes, resource recovery, and transformation products. On top of the temporal evolution, distinct spatial evolution existed in water-related research topics. Microplastics and Covid-19 causing global concerns were hot topics detected, while metagenomics and machine learning were two technical approaches emerging in recent years. These consistently popular, trending-up and emerging research topics would most likely attract continuous/increasing research input and therefore constitute a major part of the prospective water-related research publications.

Influences of granule properties on the performance of autotrophic nitrogen removal granular reactor: A model-based evaluation.

This work studied the impacts of key granule properties on the granular reactor performing partial nitritation/anammox from the modeling perspective. The results could guide not only future reliable modeling but also practical startup/operation of the reactor. To achieve high total nitrogen (TN) removal whilst avoiding significant N2O production, inoculated granules should be big and anammox-enriched. The optimum boundary layer thickness for maximum TN removal increased with the decreasing diffusivity of soluble components in the granule structure. Even though a thick boundary layer could protect anammox bacteria from elevated dissolved oxygen (DO) (e.g., 0.5 g-O2/m3) and obtain high TN removal (>90.0%) and low N2O production (<1.8%), even complete removal of the boundary layer would fail to provide sufficient substrate for anammox and therefore couldn't increase TN removal to 90.0% and decrease N2O production to <2.4% at insufficient DO (e.g., 0.3 g-O2/m3 in the presence of lifted influent NH4+ concentration).

Modeling of sulfur-driven autotrophic denitrification coupled with Anammox process.

While sulfur-driven autotrophic denitrification (SDAD) occurring in the anoxic reactor of the sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) system has been regarded as the main nitrogen removal bioprocess, little is known about the accompanying Anammox bacteria whose presence is made possible by the co-existence of NH4+ and NO2-. Therefore, this work firstly developed an integrated SDAD-Anammox model to describe the interactions between sulfur-oxidizing bacteria and Anammox bacteria. The model was subsequently used to explore the impacts of influent conditions on the reactor performance and microbial community structure of the anoxic reactor. The results revealed that at a relatively low ratio of <1.5 mg S/mg N, Anammox bacteria could survive and even take a dominant position (up to 58.9%). Finally, a modified SANI system configuration based on the effective collaboration between SDAD and Anammox processes was proposed to improve the efficiency of the treatment of sulfate-rich saline sewage.

The role of nitrification inhibitors on the removal of antibiotics in livestock wastewater by aerobic biodegradation.

An optimized aerobic-based treatment method that effectively removes antibiotics and retains ammonia is urgently needed for the field-return-based management of livestock wastewater. Allylthiourea (ATU, used for BOD determination), and 2-chloro-6-trichloromethylpyridine (TCMP) and 3,4-dimethylpyrazole phosphate (DMPP) (commonly used as nitrogen fertilizer synergists) were separately added to sequencing batch reactors (SBRs), in order to investigate their effect on nitrification inhibition and pollutant removal for livestock wastewater treatment. The laboratory test shows that the daily addition of 43.8 mg/L ATU or 17.5 mg/L TCMP to SBRs effectively inhibited nitrification. Nitrification inhibition by DMPP seemed fluctuated and insufficient even various dosing strategies were attempted. The removal efficiency of antibiotics was reduced from 95% to 85% with the addition of ATU, while not significantly influenced by TCMP and DMPP. The COD removal efficiency was reduced by only 6%-10% with the addition of three inhibitors. The pilot study shows that nitrification inhibition efficiency reached 89% with the daily addition of 11.5 mg/L TCMP. The total removal efficiency of antibiotics remained over 93%. The laboratory and pilot studies consistently demonstrate that TCMP played a satisfactory nitrification inhibition role and had a negligible effect on antibiotic removal. The current work provides a novel insight for the proper field-return-based management of livestock wastewater, which achieves the dual goals of reducing the risk of antibiotic exposure and preserving its nutrient value as fertilizers.

Novel Surrogates for Membrane Fouling and the Application of Support Vector Machine in Analyzing Fouling Mechanism.

It is difficult to recognize specific fouling mechanisms due to the complexity of practical feed water, thus the current studies usually employ foulant surrogates to carry out research, such as alginate and xanthan gum. However, the representativeness of these surrogates is questionable. In this work, the classical surrogates (i.e., alginate and xanthan gum) were systematically studied, and results showed that they behaved differently during filtration. For the mixture of alginate and xanthan gum, both filtration behaviors and adsorption tests performed by quartz-crystal microbalance with dissipation monitoring (QCM-D) indicated that alginate plays a leading role in fouling development. Furthermore, by examining the filtration behaviors of extracellular polymeric substances (EPS) extracted from practical source water, it turns out that the gel layer formation is responsible for EPS fouling, and the properties of gel layer formed by EPS share more similarities with that formed from pectin instead of alginate. In addition, with the use of experimental data sets extracted from this study and our previous studies, a modeling method was established and tested by the support vector machine (SVM) to predict complex filtration behaviors. Results showed that the small differences of fouling mechanisms lying between alginate and pectin cannot be recognized by Hermia's models, and SVM can show a discrimination as high as 76.92%. As such, SVM may be a powerful tool to predict complex filtration behaviors.

Model predicted N2O production from membrane-aerated biofilm reactor is greatly affected by biofilm property settings.

Even though modeling has been frequently used to understand the autotrophic deammonification-based membrane-aerated biofilm reactor (MABR), the relationships between system-specific biofilm property settings and model predicted N2O production have yet to be clarified. To this end, this study investigated the impacts of 4 key biofilm property settings (i.e., biofilm thickness/compactness, boundary layer thickness, diffusivity of soluble components in the biofilm structure, and biofilm discretization) on one-dimensional modeling of the MABR, with the focus on its N2O production. The results showed that biofilm thickness/compactness (200-1000 µm), diffusivity of soluble components in the biofilm structure (reduction factor of diffusivity: 0.2-0.9), and biofilm discretization (12-28 grid points) significantly influenced the simulated N2O production, while boundary layer thickness (0-300 µm) only played a marginal role. In the studied ranges of biofilm property settings, distinct upper and lower bounds of N2O production factor (i.e., the percentage ratio of N2O formed to NH4+ removed, 5.5% versus 2.3%) could be predicted. In addition to the microbial community structure, the N2O production pathway contribution differentiation was also subject to changes in biofilm property settings. Therefore, biofilm properties need to be quantified experimentally or set properly to model N2O production from the MABR correctly. As a good practice for one-dimensional modeling of N2O production from biofilm-based reactors, especially the MABR performing autotrophic deammonification, the essential information about those influential biofilm property settings identified in this study should be disclosed and clearly documented, thus ensuring both the reproducibility of modeling results and the reliable applications of N2O models.

Degradation of Polyamide Nanofiltration Membranes by Bromine: Changes of Physiochemical Properties and Filtration Performance.

The potential coexistence and interaction of bromine and polyamide membranes during membrane-based water treatment prompts us to investigate the effect of bromine on membrane performance. For fully aromatic polyamide membrane NF90 exposed under a mild bromination condition (10 mg/L), bromine incorporation resulted in more negatively charged (-13 vs -25 mV) and hydrophobic (55.2 vs 58.9°) surfaces and narrower pore channels (0.3 vs 0.29 nm). The permeabilities of water and neutral solutes were reduced by 64 and 69-87%, respectively, which was attributed to the decreased effective pore radius and hydrophilicity. NaCl permeability was reduced by 90% as a synergistic result of enhanced size exclusion and charge repulsion. The further exposure (100 and 500 mg/L bromine) resulted in a more hydrophobic surface (61.7 and 65.5°) and the minor further reduction for water and solute permeabilities (1-9%). Compared with chlorine, the different incorporation efficiency and properties (e.g., atomic size, hydrophilicity) of bromine resulted in opposite trends and/or different degrees for the variation of physicochemical properties and filtration performance of membranes. The bromine incorporation, the shift and disappearance of three characteristic bands, and the increased O/N ratio and calcium content indicated the degradation pathways of N-bromination and bromination-promoted hydrolysis under mild bromination conditions (480 mg/L·h). The further ring-bromination occurred after severe bromine exposure (4800-24,000 mg/L·h). The semi-aromatic polyamide membrane NF270 underwent a similar but less significant deteriorated filtration performance compared with NF90, which requires a different explanation.

Determination of estrogens and estrogen mimics by solid-phase extraction with liquid chromatography-tandem mass spectrometry.

An analytical method has been developed and validated for the determination of six estrogens and estrogen mimics, namely estriol (E3), bisphenol A (BPA), 17ß-estradiol (E2), estrone (E1), ethynyl estradiol (EE2) and dienestrol (DIE), with frequent occurrence in the natural environment. Solid phase extraction coupled with liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS) using electrospray ionization (ESI) in a negative mode was applied to concentration, identification, and quantification of estrogens and estrogen mimics. The SPE conditions were optimized as the selection of C18 as cartridges and MeOH as an eluent, and the control of solution pH at 9.0. The method was validated by satisfactory recoveries (80-130%) and intra-day and inter-day precision (<18.4%, as relative standard deviation), and excellent linearity for calibration curves (R2 > 0.996). The limits of detection (LODs) for six target estrogenic compounds ranged between 2.5 and 19.2 ng/L. The effects of matrix background on the determination were evaluated in terms of LODs, LOQs, analyte recovery, and slopes of calibration curves in five different water matrices. Matrix effects by tap water were negligible. However, both matrix suppression and enhancement (i.e., E3, E1, DIE) were observed in surface water and wastewater. The positive correlation between LODs and TOC in various water matrices indicated the negative effect of organic pollutants on the method sensitivity. The sum of target estrogenic compounds in environmental samples were within 17-9462 ng/L.