Electrochemically modified dissolved organic matter accelerates the combining photodegradation and biodegradation of 17α-ethinylestradiol in natural aquatic environment

Occurrence and cycle of dissolved iron mediated by humic acids resulting in continuous natural photodegradation of 17α-ethinylestradiol

17α-ethinylestradiol (EE2), a synthetic endocrine-disrupting chemical, can degrade in natural waters where humic acids (HA) and dissolved iron (DFe) are present. The iron is mostly bound in Fe(III)-HA complexes, the formation process of Fe(III)-HA complexes and their effect on EE2 degradation were explored in laboratory experiments. The mechanism of ferrihydrite facilitated by HA was explored with results indicating that HA facilitated the dissolution of ferrihydrite and the generation of Fe(III)-HA complexes with the stable chemical bonds such as C-O, CO in neutral, alkaline media with a suitable Fe/C ratio. 1O2, •OH, and 3HA* were all found to be important in the photodegradation of EE2 mediated by Fe(III)-HA complexes. Fe(III)-HA complexes could produce Fe(II) and hydrogen peroxide (H2O2) to create conditions suitable for photo-Fenton reactions at neutral pH. HA helped to maintain higher dissolved iron concentrations and alter the Fe(III)/Fe(II) cycling. The natural EE2 photodegradation pathway elucidated here provides a theoretical foundation for investigating the natural transformation of other trace organic contaminants in aquatic environments.

Effect of the molecular weight of DOM on the indirect photodegradation of fluoroquinolone antibiotics

Dissolved organic matter (DOM) is ubiquitous and widespread in natural water and influences the transformation and removal of antibiotics. Nevertheless, the influence of DOM molecular weight (MW) on the indirect photodegradation of antibiotics has rarely been reported. This study attempted to explore the influence of the molecular weight of DOM on the indirect photodegradation of two fluoroquinolone antibiotics (FQs), ofloxacin (OFL) and norfloxacin (NOR), by using UV-vis absorption and fluorescence spectroscopy. The results showed that indirect photodegradation was considered the main photodegradation pathway of FQs in DOM fractions. Triplet-state excited organic matter (3DOM*) and singlet oxygen (1O2) were the main reactive intermediates (RIs) that affected the indirect photodegradation of FQs. The indirect photodegradation rate of FQs was significantly promoted in DOM fractions, especially in the low molecular weight DOM fractions (L-MW DOM, MW < 10 kDa). The results of excitation-emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC) showed that terrestrial humic-like substances had a higher humification degree and fluorophore content in L- MW DOM fractions, which could produce more 3DOM* and 1O2 to promote the indirect photodegradation of FQs. This study provided new insight into the effects of DOM at the molecular weight level on the indirect photodegradation of antibiotics in natural water.

Emerging high-ammonia‑nitrogen wastewater remediation by biological treatment and photocatalysis techniques

The bacterial and photocatalysis techniques have been widely applied into the remediation of ammonia nitrogen wastewater. Although traditional microbial methods had been verified useful; more efficient, energy-saving and controllable candidate treatment methods are still urgently needed to cover the increasingly diverse ammonia nitrogen pollution cases. The bacterial treatment technique for ammonia nitrogen mainly depends on the ammonia nitrogen oxidation-reduction (e.g. nitrification, denitrification) by nitrifying bacteria and denitrifying bacteria, but these reactions suffer from slow denitrifying kinetic process and uncontrolled disproportionation reaction. In comparison, the photocatalysis technique based on photoelectrons is more efficient and has some advantages, such as low temperature reaction and long life, while the photocatalysis technique can not perform multiple complex biochemical reactions. Despite much scientific knowledge obtained about this issue recently, such research has yet not been widely adopted in the industry because of many concerns about subsequent catalyst stability and economic feasibility. This review summarized and discussed the very recent achievements and key problems on remediation of high-ammonia‑nitrogen wastewater and oxidation driven by bacterial treatment and photocatalysis techniques, as well as the most promising future directions for these two techniques, especially the potential of jointly bacterial-photocatalysis techniques.

MOFs-derived CuO-Fe3O4@C with abundant oxygen vacancies and strong Cu-Fe interaction for deep mineralization of bisphenol A

A novel CuO-Fe₃O₄ encapsulated in the carbon framework with abundant oxygen vacancies (CuO-Fe₃O₄@C) was successfully prepared by thermal conversion of Cu(OAc)₂/Fe-metal organic framework. The as-prepared catalyst exhibited excellent peroxymonosulfate (PMS) activation performance, good recyclability and fast magnetic separation. Under optimal conditions, the added BPA (60 mg/L) could be completely removed by CuO-Fe₃O₄@C/PMS system within 15 min with the degradation rate constant (k) of 0.32 min^-1, being 10.3 and 246.2 times that in CuO/PMS (0.031min^-1) and Fe₃O₄/PMS (0.0013 min^-1) system. A deep mineralization rate of BPA (＞80%) was achieved within 60 min. The results demonstrated the synergistic effect of bimetallic clusters, oxygen vacancies and carbon framework was a key benefit for the exposure of more active sites, the electron donor capacity and the mass transfer of substrates, thereby promoting the decomposition of BPA. Capture experiments and EPR indicated that ¹O₂ was the predominant reactive oxygen species (ROSs). The degradation routes of BPA and the activation mechanism of PMS were proposed. This study offers an opportunity to develop promising MOFs-derived hybrid catalysts with tailored structures and properties for the practical application of SR-AOPs.

Bioaugmentation removal and microbiome analysis of the synthetic estrogen 17α-ethynylestradiol from hostile conditions and environmental samples by Pseudomonas citronellolis SJTE-3

Synthetic estrogens are emerging environmental contaminants with great estrogenic activities and stable structures that are widespread in various ecological systems and significantly threaten the health of organisms. Pseudomonas citronellolis SJTE-3 is reported to degrade the synthetic estrogen 17α-ethynylestradiol (EE2) efficiently in laboratory conditions. In this work, the environmental adaptability, the EE2-degrading properties, and the ecological effects of P. citronellolis SJTE-3 under different hostile conditions (heavy metals and surfactants) and various natural environment samples (solid soil, lake water, and pig manure) were studied. Strain SJTE-3 can tolerate high concentrations of Zn²⁺ and Cr³⁺, but is relatively sensitive to Cu²⁺. Tween 80 of low concentration can significantly promote EE2 degradation by strain SJTE-3, different from the repressing effect of Triton X-100. High concentration of Tween 80 prolonged the lagging phase of EE2-degrading process, while the final EE2 removal efficiency was improved. More importantly, strain SJTE-3 can grow normally and degrade estrogen stably in various environmental samples. Inoculation of strain SJTE-3 removed the intrinsic synthetic and natural estrogens (EE2 and estrone) in lake water samples in 4 days, and eliminated over 90% of the amended 1 mg/L EE2 in 2 days. Bioaugmentation of strain SJTE-3 in EE2-supplied solid soil and pig manure samples achieved a removal rate of over 55% and 70% of 1 mg/kg EE2 within 2 weeks. Notably, the bioaugmentation of extrinsic strain SJTE-3 had a slight influence on indigenous bacterial community in pig manure samples, and its relative abundance decreased significantly after EE2 removal. Amendment of EE2 or strain SJTE-3 in manure samples enhanced the abundance of Proteobacteria and Actinobacteria, implying their potential in utilizing EE2 or its metabolites. These findings not only shed a light on the environment adaptability and degradation efficiency of strain SJTE-3, but also provide insights for bioremediation application in complex and synthetic estrogen polluted environments.

The efficient treatment of mature landfill leachate using tower bipolar electrode flocculation-oxidation combined with electrochemical biofilm reactors

Mature landfill leachate contains high concentrations of organic and inorganic compounds that inhibit the performance of conventional biological treatment. Nowadays, few single treatment techniques could fulfill the requirements of cleaning mature landfill leachate. In this study, a tower bipolar electrode flocculation-oxidation (BEF-O) reactor and an electrochemical biofilm reactor (EBR) combine device was constructed to effectively treat mature landfill leachate. And the removal efficiency and mechanism of various pollutants using the BEF-O reactor were investigated. The BEF-O system with the current density of 100 mA/cm² shows excellent treatment efficiency, which can roundly remove most pollutants (NH₄⁺-N, COD and heavy metals, etc.), and increase the bioavailability of the effluent to facilitate subsequent EBR treatment. Benefiting from the metabolic stimulation and population selection effect of electric current on microorganisms, EBR has a denser biofilm, stronger anti-pollution load capacity, superior, and stable pollution treatment efficiency. More importantly, the combined device can reduce the concentrations of COD and NH₄⁺-N from 6410 to 338 mg/L and 4065 to 4 mg/L, respectively, and has an economical energy consumption of 32.02 kWh/(kg COD) and 54.04 kWh/ (kg NH₄⁺-N). To summarize, this research could provide an innovative and industrial application prospect technology for the mature landfill leachate treatment.

Sources, characteristics, and in situ degradation of dissolved organic matters: A case study of a drinking water reservoir located in a cold-temperate forest

Dissolved organic matter (DOM) plays a pivotal role in the biogeochemical cycles of elements and the regulation of forest ecosystem functions. However, studies on the regional and seasonal characteristics of DOM in cold-temperate montane forests are still not comprehensive. In this study, samples of water, soil, and sediment from different sites in the forest drainage basin were collected, and their DOM was characterized by an excitation-emission matrix and parallel factor analysis (EEM-PARAFAC). The results showed that terrestrial-sourced humic-like substances were the dominant DOM in the studied reservoir and inflowing rivers. The quality and quantity of DOM exhibited spatiotemporal variations with the influence of terrain and monsoonal precipitation. The average concentration of dissolved organic carbon (DOC) in the wet season was 11.62 mg/L, which was higher than that in the dry season (8.18 mg/L). Higher humification index (HIX) values were observed in the wet season and upstream water than in the dry season and reservoir water. Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) was used to further develop a molecular-level understanding of the in situ degradation process of DOM. The results indicated that photodegradation rather than biodegradation may play a dominant role in the in situ degradation of terrestrial-sourced humic-like substances under natural conditions. The biodegradability of DOM was enhanced after the in situ degradation process. Additionally, a significant decrease in the precursors of disinfectant byproducts in DOM was observed after in situ degradation. To our knowledge, this is the first study of the sources, characteristics, and in situ degradation of DOM in a reservoir in a cold-temperate forest. These findings help better understand the quality, quantity, and biogeochemical process of DOM in the studied reservoir and may contribute to the selection of drinking water treatment technologies for water supply.

Durable and eco-friendly peroxymonosulfate activation over cobalt/tin oxides-based heterostructures for antibiotics removal: Insight to mechanism, degradation pathway

Potential leaching of Co ions could decrease the catalytic activity and cause secondary pollution of water, thereby threatening ecological safety and human health. In response, the in-situ generation of well-dispersed Co₂SnO₄ and SnO₂ with fine interfacial feature was constructed for PMS activation toward efficient tetracycline degradation and lower cobalt ion leaching feature. The synergistic effect of Co₂SnO₄ and SnO₂ endowed Co₂SnO₄-SnO₂ an outstanding catalytic performance for tetracycline degradation in alkaline condition. Meanwhile, the catalysts can effectively degrade the quinolones, dyes and mixture pollutant solution. The excellent performance can attributed to the in-situ introduction of SnO₂, which stabilizes the microstructure and provides an effective electronic pathway to enhance the activity of Co₂SnO₄ in the Co₂SnO₄-SnO₂. In optimized condition, the tetracycline degradation efficiency was enhanced to 94.9% within 20 min and maintained the stability at least four cycles. The degradation rate constant of Co₂SnO₄-SnO₂ was 0.149 min^-1, which was about 1.93, 2.98, 11.5 times higher than of Co₂SnO₄, Co₃O₄ and SnO₂, respectively. Notably, the leaching performance of Co₂SnO₄-SnO₂ was greatly suppressed to be 7.45 ug/L, which was lower than that of Co₂SnO₄ (6.41 mg/L) and Co₃O₄ (1.12 mg/L). Radical quenching and EPR experiments showed that singlet oxygen (¹O₂), rather than hydroxyl active species and sulfate radicals, played a predominating role for PMS activation in the Co₂SnO₄-SnO₂/PMS system. The intermediates and degradation routes for tetracycline degradation were characterized by liquid chromatograph-tandem mass spectrometry. This study expected to provide a novel strategy to construct heterostructural catalysts with lower cobalt ion leaching for the activation of PMS.

Photodegradation of propranolol in surface waters: An important role of carbonate radical and enhancing toxicity phenomenon

Antihypertensive propranolol (PRO) is frequently detected in surface waters and has adverse effects on aquatic organisms. In this study, its photochemical fate in surface water with the aspect of kinetics, products and toxicity were investigated employing steady-state photochemistry experiments and ecotoxicity tests. The results showed that photodegradation of PRO was enhanced in river water than that in phosphate buffer where dissolved organic matter (DOM), NO₃^-, and HCO₃^- played important roles. DOM accelerated the photodegradation mainly through generation of excited triplet-state DOM while NO₃^- played dual roles in the photodegradation. The reaction between excited triplet-state PRO and HCO₃^- can generate carbonate radical (CO₃^·-) to promote the photodegradation. The second-order reaction rate constant between PRO and CO₃^·- was determined to be (3.4 ± 0.8) × 10⁸ M^-1 s^-1. Eight photodegradation products were identified in the studied river water sample. Finally, the toxicity evaluated by Vibrio fischeri increased after photodegradation and three photodegradation products were responsible for the increasing toxicity, which was concluded from the significant correlation between toxicity parameters and quantity of the photodegradation products.

Dissolved Organic Matter Acting as a Microbial Photosensitizer Drives Photoelectrotrophic Denitrification

The biogeochemical fates of dissolved organic matter (DOM) show important environmental significance in aqueous ecosystems. However, the current understanding of the trophic relationship between DOM and microorganisms limits the ability of DOM to serve as a heterotrophic substrate or electron shuttle for microorganisms. In this work, we provide the first evidence of photoelectrophy, a new trophic linkage, that occurs between DOM and nonphototrophic microorganisms. Specifically, the photoelectrotrophic denitrification process was demonstrated in a Thiobacillus denitrificans-DOM coupled system, in which DOM acted as a microbial photosensitizer to drive the model denitrifier nitrate reduction. The reduction of nitrate followed a pseudo-first-order reaction with a kinetic constant of 0.06 ± 0.003 h^-1, and the dominant nitrogenous product was nitrogen. The significant upregulated (p < 0.01) expression of denitrifying genes, including nar, nir, nor, and nos, supported that the conversion of nitrate to nitrogen was the microorganism-mediated process. Interestingly, the photoelectrophic process triggered by DOM photosensitization promotes humification of DOM itself, an almost opposite trend of pure DOM irradiation. The finding not only reveals a so far overlooked role of DOM serving as the microbial photosensitizer in sunlit aqueous ecosystems but also suggests a strategy for promoting sunlight-driven denitrification in surface environments.

Biodegradation of synthetic estrogen using bioelectrochemical system and degradation pathway analysis through Quadrupole-time-of-flight-mass spectrometry

Synthetic estrogenic compounds such as 17α-ethinylestradiol (EE2) are significant environmental contaminants. This research studied the biodegradation of EE2 utilizing the EE2 adapted cells isolated from a dairy farm waste site in suspension flask vis-a-vis Bioelectrochemical System (BES) and compared the power output in the BES with and without EE2 as a co-substrate. 78% removal of EE2 was observed in the BES as against 60% removal in suspension flasks. The maximum power density in the BES increased about 53% when EE2 is used as a co-substrate. The EE2 biodegradation studied using HPLC and Q-TOF methods, also proposes a hypothetical pathway for EE2 degradation by the newly isolated strain Rhodopseudomonas palustris MDOC01 and reports the significant metabolites like nicotinic acid and oxoproline being detected during bioelectrochemical treatment process of EE2. Study also suggests that Plasma peroxide treatment of anode material enhanced the overall performance in terms of biodegradation efficiency and power output.

Enhanced periphyton biodegradation of endocrine disrupting hormones and microplastic: Intrinsic reaction mechanism, influential humic acid and microbial community structure elucidation

Endocrine-disrupting compounds (EDCs), as well as microplastics, have drawn global attention due to their presence in the aquatic ecosystem and persistence in wastewater treatment plants (WWTPs). In the present study, for simultaneous bio-removal of two EDCs, 17α-ethinylestradiol (EE2), bisphenol A (BPA), and a microplastic, polypropylene (PP) four kinds of periphytic biofilms were employed. Additionally, the effect of humic acid (HA) on the removal efficacy of these biofilms was evaluated. It was observed that EE2 and BPA (0.2 mg L^-1 each) were completely (∼100%) removed within 36 days of treatment; and the biodegradation of EE2, BPA, and PP was significantly enhanced in the presence of HA. Biodegradation of EE2 and BPA was evaluated through Ultra-high performance liquid chromatography (UHPLC), and Gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) was used to determine the mechanism of degradation. Gel permeation chromatography (GPC) and SEM had validated the biodegradation of PP (5.2-14.7%). MiSeqsequencing showed that the community structure of natural biofilm changed after the addition of HA, as well as after the addition of EDCs and PP. This change in community structure might be a key factor regarding variable biodegradation percentages. The present study revealed the potential of periphytic biofilms for the simultaneous removal of pollutants of different chemical natures, thus provides a promising new method for wastewater treatment applications.

Different performance of pyrene biodegradation on metal-modified montmorillonite: Role of surface metal ions from a bioelectrochemical perspective

Microbial extracellular electron transfer (EET) at microbe-mineral interface has been reported to play a significant role in pollutant biotransformation. Different metals often co-exist with organic pollutants and are immobilized on mineral surfaces. However, little is known about the influence of mineral surface metal ions on organic pollutant biodegradation and the involved electron transfer mechanism. To address this knowledge gap, pyrene was used as a model compound to investigate the biodegradation of polycyclic aromatic hydrocarbon on montmorillonite mineral saturated with metal ions (Na(I), Ni(II), Co(II), Cu(II) and Fe(III)) by Mycobacteria strain NJS-1. Further, the possible underlying electron transfer mechanism by electrochemical approaches was investigated. The results show that pyrene biodegradation on montmorillonite was markedly influenced by surface metal ions, with degradation efficiency following the order Fe(III) > Na(I) ≈ Co(II) > Ni(II) ≈ Cu(II). Bioelectrochemical analysis showed that electron transfer activities (i.e., electron donating capacity and electron transport system activity) varied in different metal-modified montmorillonites and were closely related to pyrene biodegradation. Fe(III) modification greatly stimulated degrading enzyme activities (i.e., peroxidase and dioxygenase) and electron transfer activities resulting in enhanced pyrene biodegradation, which highlights its potential as a technique for pollutant bioremediation. The bacterial extracellular protein and humic substances played important roles in EET processes. Membrane-bound cytochrome C protein and extracellular riboflavin were identified as the electron shuttles responsible for transmembrane and cross extracellular matrix electron transfer, respectively. Additions of exogenetic electron mediators of riboflavin, humic acid and potassium ferricyanide accelerated pyrene biodegradation which further verified the critical role of EET in PAH transformation at bacteria-mineral interfaces. These results support the development of clay mineral based advanced bioremediation techniques through regulating the electron transfer processes at the microbe-mineral interfaces by mineral surface modification.

17α-Ethinylestradiol (EE2): concentrations in the environment and methods for wastewater treatment – an update

17α-Ethinylestradiol (EE2) is a frequently used drug and an endocrine disruptive substance. Adverse effects on biota have been reported when they are exposed to this substance in the environment. The last review on EE2 in the environment was published in 2014. Since then, well above 70 studies on EE2 and related substances have been published. The aim of this review was therefore to bring together recent data with earlier ones. The topics emphasized were observable trends of environmental levels of EE2 and methods to reduce EE2 levels in wastewater, before it can enter the environment. This should give an overview of the recent knowledge and developments regarding these environmental aspects of EE2. In the studies discussed, EE2 levels in surface waters were well detectable in many countries, both above and below the predicted no effect concentration (PNEC) of 0.035 ng L⁻¹, although analytical methods used for the quantification often are unsatisfactory regarding their limit of detection. To support the degradation of EE2 prior to entry into the environment, appropriate treatment methods could help to control the emissions of EE2. Several methods for the reduction of EE2 levels of up to 100% removal efficiency were reported recently and are of chemical, biological, adsorptive or ion-exchange nature. Depending on the required properties like initial EE2 concentration or treatment duration, several promising methods are available.

17α-Ethinylestradiol (EE2) is a frequently used drug and an endocrine disruptive substance.

Characterization and biogeochemical implications of dissolved organic matter in aquatic environments

Dissolved organic matter (DOM) is viewed as one of the most chemically active organic substances on earth. It plays vital roles in the fate, bioavailability and toxicity of aquatic exogenous chemical species (e.g., heavy metals, organic pollutants, and nanomaterials). The characteristics of DOM such low concentrations, salt interference and complexity in aquatic environments and limitations of pretreatment for sample preparation and application of characterization techniques severely limit understanding of its nature and environmental roles. This review provides a characterization continuum of aquatic DOM, and demonstrate its biogeochemical implications, enabling in-depth insight into its nature and environmental roles. A synthesis of the effective DOM pretreatment strategies, comprising extraction and fractionation methods, and characterization techniques is presented. Additionally, the biogeochemical dynamics of aquatic DOM and its environmental implications are discussed. The findings indicate the collection of representative DOM samples from water as the first and critical step for characterizing its properties, dynamics, and environmental implications. However, various pretreatment procedures may alter DOM composition and structure, producing highly variable recoveries and even influencing its subsequent characterization. Therefore, complimentary use of various characterization techniques is highly recommended to obtain as much information on DOM as possible, as each characterization technique exhibits various advantages and limitations. Moreover, DOM could markedly change the physical and chemical properties of exogenous chemical species, influencing their transformation and mobility, and finally altering their potential bioavailability and toxicity. Several research gaps to be addressed include the impact of pretreatment on the composition and structure of aquatic DOM, molecular-level structural elucidation for DOM, and assessment of the effects of DOM dynamics on the fate, bioavailability and toxicity of exogenous chemical species.

Modified humic acids mediate efficient mineralization in a photo-bio-electro-Fenton process

Humic acids (HA) are common mediators in redox reactions in the aquatic environment. The structures and properties of HA are greatly influenced by environmental factors such as external electrons. In this study, qualitative changes in electron-modified HA and the underlying mechanisms were reported, which not only contribute to understanding the fate of HA and their impact on organic pollutants, but could facilitate their potential use for water purification. The photochemical activity and electron-donating capacity of HA were improved due to the increase of phenolic and carboxyl components via the reduction modification by electrons, creating a novel and efficient photo-bio-electro-Fenton system mediated by HA under neutral conditions without the use of hydrogen peroxide (H₂O₂). The in-situ continuous production of H₂O₂ ensured an adequate supply of hydroxyl radicals in this coupled system, achieving mineralization (92%) of HA and 17α-ethinylestradiol (EE2), a common synthetic estrogen with high estrogenic potency. Two degradation pathways with five degradation intermediates of EE2 were identified in our study. Effluents from the coupled system showed decreased endocrine-disrupting activity. Our findings demonstrated a new approach for the in-situ modification and potential use of HA for water treatment and particularly the concurrent degradation of HA and organic pollutants through a photo-bioelectrochemical system mediated by HA.

Synergistic activation of peroxymonosulfate via in situ growth FeCo2O4 nanoparticles on natural rectorite: Role of transition metal ions and hydroxyl groups

Developing low-cost, high-efficiency catalysts for advanced oxidation processes remain a key issue for the degradation of organic pollutants. In this study, a novel FeCo₂O₄/rectorite composite was synthesized via a facile combustion process and employed to activate peroxymonosulfate (PMS) for dealing with atrazine (ATZ). The addition of rectorite could result in higher specific surface area, smaller pore size and more hydroxyl groups, which were beneficial to enrich pollutants to the adsorption sites and provide sufficient reactive sites. After meticulous evaluation, the degradation efficiency of FeCo₂O₄/rectorite composite towards ATZ exhibited improved PMS activation efficiency which was about 2.6 times than that of pure FeCo₂O₄. Based on the characterization results, the sulfate radicals and hydroxyl radicals were considered to be the main free radicals which were involved into the circulation of Co(II)-Co(III)-Co(II) as well as the oxidation of ≡Fe(II), which was responsible for the remarkable catalytic efficiency. In addition, the chemical stability and superior catalytic performance of FeCo₂O₄/rectorite should also be attributed to the chemical combination between metal ions and the surface hydroxyl groups of rectorite. Overall, these findings are beneficial for understanding the mechanism of PMS activation by natural mineral-based catalysts and contributing to the practical application of sulfate-based technology for organic wastewater treatment.

Indirect photodegradation of sulfadiazine in the presence of DOM: Effects of DOM components and main seawater constituents

The presence of pharmaceuticals and personal care products in coastal waters has caused concern over the past decade. Sulfadiazine (SD) is a very common antibiotic widely used as human and fishery medicine, and dissolved organic matter (DOM) plays a significant role in the indirect photodegradation of SD; however, the influence of DOM compositions on SD indirect photodegradation is poorly understood. The roles of reactive intermediates (RIs) in the indirect photolysis of SD were assessed in this study. The reactive triplet states of DOM (³DOM∗) played a major role, whereas HO· and ¹O₂ played insignificant roles. DOM was divided into four components using excitation-emission matrix spectroscopy combined with parallel factor analysis. The components included three allochthonous humic-like components and one autochthonous humic-like component. The allochthonous humic-like components contributed more to RIs generation and SD indirect photolysis than the autochthonous humic-like component. A significant relationship between the indirect photodegradation of SD and the decay of DOM fluorescent components was found (correlation coefficient, 0.99), and the different indirect photodegradation of SD in various DOM solutions might be ascribed to the different components of DOM. The indirect photolysis rate of SD first increased and then decreased with increasing pH. SD photolysis was enhanced by low salinity but remained stable at high salinity. The increased carbonate concentration inhibited SD photolysis, whereas nitrate showed almost no effect in this study.

Leachability of endocrine disrupting chemicals (EDCs) in municipal sewage sludge: Effects of EDCs interaction with dissolved organic matter

In this study, experiments were performed to assess the significance of dissolved organic matter (DOM) on the leachability of four common EDCs, i.e., bisphenol A (BPA), 17α-ethinylestradiol (EE2), progesterone (PGT) and testosterone (TST), in municipal sewage sludge (MSS) under landfill conditions. The DOM was derived from two sources: MSS (MDOM), and natural soil represented by organic matter obtained from the Suwannee River (NDOM). Fluorescence excitation-emission matrix quenching combined with parallel factor analysis was adopted to characterize the interaction properties between the EDCs and DOM. The accumulative leachability of the target EDCs ranged from 0.09% (PGT) to 3.8% (TST). In particular, the leaching of BPA, EE2 and TST followed S-shaped curves, while PGT exhibited continuous leaching potential in untreated MSS. With the introduction of DOM, (i) the leachability of BPA and EE2 increased to 13.4% and 61.6%, respectively, whereas those of PGT and TST declined by 61.3% and 45.8%, respectively, and (ii) BPA, EE2 and PGT no longer reached leaching equilibrium but the S-shaped leaching property of TST persisted. The differential effects of MDOM and NDOM at identical concentrations on the EDCs leachability increased with curing time. BPA, EE2 and PGT quenched the MDOM fluorophores attributed to aromatic protein-like components. The fluorescence quenching of NDOM by BPA, EE2 and PGT was centered on soluble microbial by-product-like and humic-like substances. Compared with PGT, EE2 and BPA had greater capability for binding with DOM components largely via hydrophobic interactions, whereas PGT preferentially interacted with the DOM hydrophilic functionalities through specific interactions. TST had no binding capability but displayed potentials competing for sorption sites with DOM moieties. Our findings suggested that the management of MSS increased the risk of environmental contamination by EDCs for a long duration and that DOM was a useful indicator to predict the migration and transport properties of EDCs.

Photoelectrocatalytic simultaneous removal of 17α-ethinylestradiol and E. coli using the anode of Ag and SnO2-Sb 3D-loaded TiO2 nanotube arrays

Reclaimed water contains both residual contaminants and pathogenic microorganisms while their simultaneous removal has not been fully addressed. Thus, a photoelectrocatalytical system (PEC) was engineering herein using an innovatively synthesized composite of TiO₂ nanotube arrays (TNTs) decorated with antimony doped tin oxide (SnO₂-Sb) and silver nanoparticles (Ag) in three dimensions (TNTs-Ag/SnO₂-Sb) to realize the simultaneous removal of 17α-ethinylestradiol (EE2) and Escherichia coli (E. coli). The optical and electrochemical properties of TNTs were improved after the loading of Ag and SnO₂-Sb with an excellent the stability for reuse. A 68% removal of EE2 and more than 5-log removal of E. coli were achieved in 1 h in PEC. The DNA activity of E. coli was nearly completely lost after PEC treatment and the cytotoxicity of PEC treated EE2 solution was significantly reduced. Reactive species (HO and H₂O₂) and degradation products of EE2 were identified, and the transformation pathways were proposed accordingly. This study generates valuable information of the transformation kinetics and mechanism for simultaneous removal of EE2 and E coli. It also provides an effective and innovative technology for water reuse.

Rapid visible-light degradation of EE2 and its estrogenicity in hospital wastewater by crystalline promoted g-C3N4

Metal-free, chemically activated crystalline graphitic carbon nitride (g-C₃N₄) nanorods with enhanced visible-light photoactivity demonstrated rapid photodegradation of 17α-ethinylestradiol (EE2) in water and real hospital wastewater. Pure g-C₃N₄ and another three crystalline promoted g-C₃N₄ photocatalysts developed by hydrothermal method were characterized by, High-Resolution Transmission Electron Microscopy (HRTEM), X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), Photoluminescence (PL), Electron spin resonance (ESR), X-ray Photoelectron Spectroscopy (XPS) and Diffuse Reflectance Spectroscopy (DRS). Hydrothermal-based chemical activation did not alter the crystal structure, functional group or surface morphology, but it enhanced the specific surface area of activated g-C₃N₄ due to intralayer delamination and depolymerization of g-C₃N₄. Compared to pure g-C₃N₄, the activated g-C₃N₄-3 demonstrated efficient degradation of EE2 (<30 min, 3 mg/l) by visible wavelengths of the solar spectrum. This work provides advanced insight into the construction of heterojunction visible-light photocatalysts and production of O₂^- via reduction of O₂ with photogenerated electrons. Proposed and derived mechanism for photodegradation of EE2 by g-C₃N₄-3 using gas chromatography-mass spectrometry (GCMS). Yeast Estrogen Screen (YES) was performed to evaluate the estrogenicity of treated water samples. Efficient removal of EE2 estrogenic activity (<45 min, 3 mg/l) was achieved using the visible light-activated g-C₃N₄. Estrogenicity removal rate corresponded well with EE2-degradation rate.

Optical characteristics and cytotoxicity of dissolved organic matter in the effluent and sludge from typical sewage treatment processes

The environmental ecological risks of dissolved organic matter (DOM) extracted from diverse sewage treatment plants and processes have attracted urgent attention. The correlations between the toxicity of DOM and its compositions or properties deserved to be explored to evaluate the environmental risk. Human liver cancer (HepG2) and normal liver (L02) cell lines were used in in vitro experiments evaluating the environmental risks of dissolved organics discharged from secondary and advanced sewage treatment processes. Organics extracted from dewatered sludge were also tested. Elemental compositions were determined and optical characterization was performed. The results indicated that the organics in the effluent from anaerobic-anoxic-oxic processes contained more oxygen-containing groups and hydrophilic substances than those in other types of effluent. The sludge extracts showed the greatest cytotoxicity, followed by the effluent from secondary treatment and then the effluent from an advanced treatment process. The sludge extracts inhibited cell proliferation while the other effluents promoted it at a 5 mgC/L concentration. The organics discharged from secondary and advanced treatment processes induced relatively little production of reactive oxygen species. That stimulated cell self-repair and free radical scavenging and consequently resulted in cell proliferation with the cell lines tested. Oxygen-containing groups in the dissolved organics promoted cell proliferation and ROS removal. The atomic ratios and UV spectroscopy indices contributed mainly to the cell viability among the positive indicators. These results provide theoretical basis for managing the ecological risks posed by dissolved organics released from sewage treatment processes.

Characterization of an efficient estrogen-degrading bacterium Stenotrophomonas maltophilia SJTH1 in saline-, alkaline-, heavy metal-contained environments or solid soil and identification of four 17β-estradiol-oxidizing dehydrogenases

The efficient bioremediation of estrogen contamination in complex environments is of great concern. Here the strain Stenotrophomonas maltophilia SJTH1 was found with great and stable estrogen-degradation efficiency even under stress environments. The strain could utilize 17β-estradiol (E2) as a carbon source and degrade 90% of 10 mg/L E2 in a week; estrone (E1) was the first degrading intermediate of E2. Notably, diverse pH conditions (3.0-11.0) and supplements of 4% salinity, 6.25 mg/L of heavy metal (Cd²⁺ or Cu²⁺), or 1 CMC of surfactant (Tween 80/ Triton X-100) had little effect on its cell growth and estrogen degradation. The addition of low concentrations of copper and Tween 80 even promoted its E2 degradation. Bioaugmentation of strain SJTH1 into solid clay soil achieved over 80% removal of E2 contamination (10 mg/kg) within two weeks. Further, the whole genome sequence of S. maltophilia SJTH1 was obtained, and a series of potential genes participating in stress-tolerance and estrogen-degradation were predicted. Four dehydrogenases similar to 17β-hydroxysteroid dehydrogenases (17β-HSDs) were found to be induced by E2, and the four heterogenous-expressed enzymes could oxidize E2 into E1 efficiently. This work could promote bioremediation appliance potential with microorganisms and biodegradation mechanism study of estrogens in complex real environments.

Bismuth impregnated biochar for efficient estrone degradation: The synergistic effect between biochar and Bi/Bi2O3 for a high photocatalytic performance

An innovative advanced oxidation process was successfully developed to photocatalytic-degradation of estrone through the synergistic effect of biochar and Bi/Bi₂O₃ in bismuth-containing photocatalytic biochar (BiPB). The highest reaction rate constant (k_obs) of estrone degradation by BiPB was 0.045 min^-1 under the conditions of initial concentration of estrone =10.4 μmol L^-1, [BiPB] =1 g L^-1, pH = 7.0. The k_obs was almost tenfold and more than 20 times than that of biochar without bismuth impregnation and pristine Bi/Bi₂O₃, respectively. The best photocatalytic performance of BiPB composites for the degradation of estrone was primarily attributed to generation of OH radicals. Impregnation of bismuth helped control the concentration of persistent free radicals (PFRs) and develop a hierarchical porous structure of biochar. The presence of biochar facilitated pre-concentration estrone on BiPB and improved the separation and transfer efficiency of charge carriers. The synergistic effect between biochar and Bi/Bi₂O₃ contributed to the generation of OH radicals for estrone degradation under neutral pH conditions. The transformation pathway of estrone was also proposed based on the measured transformation products in the presence of BiPB. The high efficiency of BiPB composites indicated that this easily-obtained material was promising for estrone-wastewater treatment applications as a low-cost composite photocatalyst.

Predictive role of spectral slope ratio towards 17α-ethynylestradiol photodegradation sensitized by humic acids

Humic acids (HAs) have been shown to dominate the photodegradation of steroid estrogens in natural waters. Nevertheless, how the photosensitizing ability of HAs relates to their structural and optical characteristics remains largely unknown. In this study, 17α-ethynylestradiol (EE2) was selected as a model compound to study to what extent easily-measurable characteristics of HAs might be used to predict their photosensitization potency. HAs were extracted from sediments of two different sources, and then subjected to structural and optical properties characterization using elemental analyzer, UV-vis spectroscopy and fluorescence spectroscopy. Photochemical experiments show that the HAs from the two sources can effectively meditate EE2 photodegradation. Although with drastically different structural and optical properties, the photosensitizing ability of these HAs towards EE2 can be well described by simple linear regressions using a spectroscopic index, the spectral slope ratio (S_R). This optical indicator is correlated with various physicochemical properties of HAs, including the molecular weight, lignin content, charge-transfer interaction potential, photobleaching extent and sources. No universal prediction model could be established for predicting EE2 photodegradation kinetics on the basis of S_R, but in specific waters S_R could be a powerful indictor for predicting the EE2 photodegradation sensitized by HAs.

Dissolved organic matter mediates in the anaerobic degradation of 17α-ethinylestradiol in a coupled electrochemical and biological system

Dissolved organic matter (DOM) can act as an electron shuttle in biogeochemical redox reactions to affect the fate of contaminants. Herein DOMs were tested for their ability to mediate in the degradation of 17α-ethinylestradiol (EE2) in a coupled electrochemical and biological system. Fulvic acid (FA) and Sigma humic acid (SHA) were found to promote degradation by the electro-domesticated micro-organisms in the coupled system. Analyses of superoxide dismutase levels, microbial community and clusters of orthologous groups of proteins showed that electrical stimulation promoted their growth and metabolism. It was confirmed that electron transfer in the coupled system was promoted in the presence of DOM as their protein-like components were converted into aromatic substances. The electrical stimulation improved the microorganisms' effectiveness in subsequent biodegradation under anaerobic condition. Stimulated micro-organisms seemed to increase their environmental tolerance and degrade EE2 effectively. These findings provide evidence about the fate of estrogens in bioelectrochemical water treatment.

Biochar enhanced microbial degradation of 17β-estradiol

Steroid estrogens (SEs), especially 17β-estradiol (E2), can be a serious threat to the health of organisms. The removal of E2 from the natural environment is mainly carried out by microbial degradation partly mediated by biochar, which contains quinone structures. In this study, reed straw biochar samples made at four different heat treatment temperatures (HTTs) were used to mediate E2 microbial degradation by Shewanella oneidensis MR-1. The removal efficiency of E2 (95%) was highest in the presence of HTT - 500 °C biochar under anaerobic conditions after 120 h of microbial degradation. The effect of biochar on promoting microbial degradation was far more superior under anaerobic conditions than under aerobic conditions. The redox-activity and types of surface functional groups of biochar reveal that biochar can accept electrons generated by microorganisms in a timely manner. This mechanism promotes the metabolic process of cells and microbial degradation of E2 (exponential increase). Biochar particles rather than biochar-derived water-soluble organic compounds are responsible for this stimulating effect. These results highlight the impact that biochar has on microbial degradation of trace pollutants in a natural environment.

Ecotoxicological effects and removal of 17β-estradiol in chlorella algae

17β-estradiol (E2) is a steroid estrogen able to affect the reproduction of aquatic organisms even at extremely low concentrations. The behavior of E2 in the presence of chlorella algae was investigated in laboratory experiments. The results showed that the algae's growth was inhibited by 26% after 7 days of culturing in a 2.0 mg L^-1 solution of E2. The 96 h EC₅₀ value of 21.46 mg L^-1 reflected moderate toxicity. Even low concentrations of E2 were found to affect total chlorophyll and carotenoid levels after 7 and 10 days and to alter stress-generated enzymatic activity in the algae. The efficiency of chlorella's E2 degradation decreased with the increasing of E2 concentration, but 92% of the E2 can be removed from a 0.5 mg L^-1 solution over 10 days. The degradation mechanism was speculated. The microalgae suffered relatively less growth inhibition at low E2 concentrations, and their removal effectiveness was then better. The data help to elucidate the interaction between chlorella algae and E2 in an aquatic environment.

Intermittent light and microbial action of mixed endogenous source DOM affects degradation of 17β-estradiol day after day in a relatively deep natural anaerobic aqueous environment

All kinds of wastewaters containing steroid estrogens (SEs) and mixed endogenous source dissolved organic matter (DOM) enter natural water environments with intermittent illumination where microbial action occurs in a relatively deep natural aqueous environment. The role of mixed endogenous source DOM in SEs' biodegradation and photochemical degradation in such environments was studied using 17β-estradiol (E2) in laboratory experiments under anaerobic conditions. The experimental results show that microbial action can improve the optical properties and electron transfer capability of mixed endogenous source DOM, promoting photodegradation and biodegradation. Intermittent illumination attenuates DOM's electron transfer capacity and its chromophore groups, but it improves the bioavailability of low molecular weight dissolved organic matter which promotes microbial growth under anaerobic conditions. DOM-mediated co-degradation by light and microbial action over three days was better than either individually. The presence of Fe(III) promoted electron transfer, and Fe(III)-DOM complexes accelerated energy transfer under irradiation, enhancing photodegradation. Any remaining estrogens will continue to degrade, most effectively in well-aerated waters with sufficient illumination.

Isolation and characterization of an estrogen-degrading Pseudomonas putida strain SJTE-1

In this report, Pseudomonas putida SJTE1 isolated from an enrichment culture of sludge was confirmed to degrade natural estrogens (17β-estradiol, estrone, estriol), estrogenic chemicals (naphthalene and phenanthrene) and testosterone. The strain completely degraded 1 mg/L 17β-estradiol in 24 h and transformed it into estrone; 90% and 75% of 50 mg/L and 100 mg/L 17β-estradiol were utilized in 7 days, respectively. The transformation efficiency of this strain against natural estrogens was much higher than that against other estrogenic chemicals. Organic carbon sources, lipopolysaccharide and surfactants could enhance the degradation efficiency of strain SJTE-1 against 17β-estradiol. The adsorption of 17β-estradiol onto the biomass was the premise for transmembrane and cellular utilization of this chemical. This work has the potential to bioremediate the environmental estrogens.

Dissolved organic matter and estrogen interactions regulate estrogen removal in the aqueous environment: A review

This review summarizes the characterization and quantification of interactions between dissolved organic matter (DOM) and estrogens as well as the effects of DOM on aquatic estrogen removal. DOM interacts with estrogens via binding or sorption mechanisms like π-π interaction and hydrogen bonding. The binding affinity is evaluated in terms of organic-carbon-normalized sorption coefficient (Log K_OC) which varies with types and composition of DOM. DOM has been suggested to be a more efficient sorbent compared with other matrices, such as suspended particulate matter, sediment and soil; likely associated with its large surface area and concentrated carbon content. As a photosensitizer, DOM enhanced estrogen photodegradation when the concentration of DOM was below a threshold value, and when above, the acceleration effect was not observed. DOM played a dual role in affecting biodegradation of estrogens depending on the recalcitrance of the DOM and the nutrition status of the degraders. DOM also acted as an electron shuttle (redox mediator) mediating the degradation of estrogens. DOM hindered enzyme-catalyzed removal of estrogens while enhanced their transformation during the simultaneous photo-enzymatic process. Membrane rejection of estrogens was pronounced for hydrophobic DOM with high aromaticity and phenolic moiety content. Elimination of estrogens via photolysis, biodegradation, enzymolysis and membrane rejection in the presence of DOM is initiated by sorption, accentuating the role of DOM as a mediator in regulating aquatic estrogen removal.