Electro living membrane bioreactor for highly efficient wastewater treatment and fouling mitigation: Influence of current density on process performances.

The next generation of the self-forming dynamic membrane, referred to in this study as the "Living Membrane (LM)", is a new patented technology based on an encapsulated biological layer that self-forms on a designed coarse-pore size support material during wastewater treatment and acts as a natural membrane filter. Integrating electrochemical processes with wastewater treatment using the LM approach has also been recently studied (the reactor is referred to as the Electro-Living Membrane Bioreactor or e-LMBR). This study investigated the effects of varying current densities, i.e., 0.3, 0.5, and 0.9 mA/cm2, on the performance of an e-LMBR. The results were also compared with those of the Living Membrane Bioreactor or LMBR (without applied current density). Higher pollutant removals were observed in the presence of the electric field. However, the effect of varying applied current densities on the COD (98-99 %), NH3-N (97-99 %), and PO43-P (100 %) removals was not statistically significant. The more prominent differences (p < 0.05) were observed in the decrease of NO3--N concentrations from mixed liquor to effluent, with increasing current density resulting in lower mean NO3--N effluent concentrations (0.3 mA/cm2: 6.13 mg/L; 0.5 mA/cm2: 4.38 mg/L; 0.9 mA/cm2: 3.70 mg/L). The reduction of NO3--N concentrations as wastewater permeated through the LM layer also confirmed its role in removing nitrogen-containing compounds. Higher current densities resulted in lower concentrations of fouling substances, particularly those of microbial extracellular polymeric substances (EPS) and transparent exopolymer particles (TEPs). The average values of the temporal variation of transmembrane pressure (d(TMP)/d(t)) in the e-LMBR were extremely low, in the range of 0.013-0.041 kPa/day, throughout the operation period. The highest (d(TMP)/d(t)) was observed for the highest current density. However, the TMP values remained below 2 kPa in all the e-LMBR runs even after the initial LM formation stage.

Microalgae to biodiesel: A novel green conversion method for high-quality lipids recovery and in-situ transesterification to fatty acid methyl esters.

Greenhouse gases (GHGs) emissions due to increasing energy demand have raised the need to identify effective solutions to produce clean and renewable energy. Biotechnologies are an effective platform to attain green transition objectives, especially when synergically integrated to promote health and environmental protection. In this context, microalgae-based biotechnologies are considered among the most effective tools for treating gaseous effluents and simultaneously capturing carbon sources for further biomass valorisation. The production of biodiesel is regarded as a promising avenue for harnessing value from residual algal biomass. Nonetheless, the existing techniques for extracting lipids still face certain limitations, primarily centred around the cost-effectiveness of the process.This study is dedicated to developing and optimising an innovative and cost-efficient technique for extracting lipids from algal biomass produced during gaseous emissions treatment based on algal-bacterial biotechnology. This integrated treatment technology combines a bio-scrubber for degrading gaseous contaminants and a photobioreactor for capturing the produced CO2 within valuable algal biomass. The cultivated biomass is then processed with the process newly designed to extract lipids simultaneously transesterificated in fatty acid methyl esters (FAME) via In Situ Transesterification (IST) with a Kumagawa-type extractor. The results of this study demonstrated the potential application of the optimised method to overcome the gap to green transition. Energy production was obtained from residuals produced during the necessary treatment of gaseous emissions. Using hexane-methanol (v/v = 19:1) mixture in the presence KOH in Kumagawa extractor lipids were extracted with extraction yield higher than 12% and converted in fatty acid methyl esters. The process showed the enhanced extraction of lipids converted in bio-sourced fuels with circular economy approach, broadening the applicability of biotechnologies as sustainable tools for energy source diversification.

A universal model to predict yields of THMs and HAAs based on UV-Visible absorption spectra.

Differential absorption spectroscopy (DAS) quantifies changes in the UV-Visible absorbance of dissolved organic matter (DOM) caused by reactions of its chromophores. As a result of its precision and sensitvity, DAS serves as a powerful tool for characterizing the formation of disinfection by-products (DBPs) in generated in DOM chlorination reactions. However, the nonlinear relationship between the intensity of DAS and DBP concentrations as well as the need to develop site-specific fitting parameters limit its practical applications. This study investigated the physico-chemical nature of DAS of chlorinated DOM through experimental measurements and theoretical calculations. Results of this study provide molecular-level evidence that electrophilic substitution reactions involving DOM reactive sites result in the emergence of DAS feaures ascribed to the "fast" chromophores. The ring opening in the cyclic enones-like structures which can be present either in the original DOM or are generated as intermediates in its chlorination, leads to the emergence of DAS features associated with the "slow" chromophores and high yields of DBPs. The kinetic study of chlorination of real waters reveals a strong linear relationship (R2 > 0.91) between ln([DBP]) and the long-wavelength (λ > 325 nm) parameter of the DAS, notably (ln(-DA350)). This relationship varies among different water sources due to the differences in the heterogeneity of Band A3 whose maximum is near 350 nm. Band A3 is one of the Gaussian bands that comprise the overall UV-Visible spectrum of DOM. A new function (f(-DA350)) is proposed in this study to quantify DBP formation. This function, which is determined by the Band A3's area, allows establishing a universal linear relationship between f(-DA350) and ln([THMs]), as well as f(-DA350) and ln([HAAs]), across various water sources. The findings of this study will stimulate further development of spectroscopy-based DBP monitoring technology for monitoring and optimization of water disinfection processes.

Characterizing photochemical production carboxyl content of dissolved organic matters using absorbance spectroscopy combined with FT-ICR MS.

Irradiation can significantly impact the structure, reactivity and environmental behavior of dissolved organic matter (DOM). The extent of these processes remains to be ascertained in more detail but the heterogeneity and site-specificity of DOM, and the lack of methods to characterize DOM at its environmentally-relevant concentrations make it a challenge. In this study, the differences of DOM response to photodegradation in four typical origins (i.e., surface water, sediment and intracellular and extracellular algal DOM) were tracked on the molecular-level using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). Changes of the carboxyl and phenolic DOM moieties induced by irradiation were quantified by spectroscopic titrations, and the mechanism of functional groups affecting the changes of specific molecular composition was qualitatively proposed. The results demonstrated that intracellular algal organic matter (I-DOM) was most susceptible to photodegradation (ca. 63% DOM loss), then came extracellular algal organic matter (E-DOM) and surface water DOM (W-DOM) (ca. 15% DOM loss). Sediment DOM (S-DOM) was most resistant to irradiation, with a very small level of its mineralization. Lipids, lignin-like compounds and tannin-like compounds in I-DOM and E-DOM were relatively photo-labile. The photodegradation of lipids was related to the decarboxylation of carboxyl functional groups, while the photodegradation of tannin-like compounds was related to the rupture of phenolic functional groups. In comparison, the molecular composition of W-DOM and S-DOM was less affected by irradiation, which was also reflected in the fact that the carboxyl and phenolic functional groups were highly photo-resistant. This study showed that the photoactivity of DOM in surface water was closely related to the abundance of algae, so controlling the excessive reproduction of algae may have a positive effect on stability of quality and quantity of organic matter in surface water.

Interpreting pH-Dependent Differential UV/VIS Absorbance Spectra to Characterize Carboxylic and Phenolic Chromophores in Natural Organic Matter.

Natural organic matter (NOM) is critical for the biogeochemical cycles of energy and many elements in terrestrial and aquatic ecosystems, and protonation-active functional groups in NOM molecules, notably carboxylic and phenolic groups often mediate these critical environmental functions. Molecular heterogeneity, polydispersity and dynamic behavior of NOM complicate achieving an unambiguous description of its molecular properties and reactivity. This study demonstrates that differential ultraviolet-visible (UV/VIS) absorbance spectra (DAS) of NOM acquired at varying pH values exhibit several distinct features associated with the deprotonation of NOM molecules, independent of the environmental provenance of NOM (e.g., surface water, seawater, sediment, and wastewater). The protonation-active functionalities that contribute to the Gaussian distribution bands present in the DAS were identified here by comparing characteristic properties of the bands with the stoichiometries of NOM molecules ascertained by Ultrahigh-Resolution Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS). The protonation-active individual chromophores universally present in NOM molecules were identified by a genetic molecular network analysis. The observed DAS features were closely modeled via superimposing DAS spectra of 51 individual protonation-active chromophores. Molecular orbital theory was applied to further interpret the deprotonation of these chromophores, their molecular structure, electron distribution, and electron transitions measured using DAS. The high sensitivity and easy implementation of the DAS approach allows using it as a powerful tool to quantify the molecular properties and reactivity of NOM at environmental concentrations.

Biological desulfurization of biogas: A comprehensive review on sulfide microbial metabolism and treatment biotechnologies.

Hydrogen sulphide (H2S) removal from biogas is of high relevance as it damages combustion engines used for heat and power generation and causes adverse public health and environmental effects. Biological processes have been reported as a cost-effective and promising approach to desulfurize biogas. This review presents a detailed description of the biochemical foundations of the metabolic apparatus of H2S oxidizing bacteria, namely chemolithoautotrophs and anoxygenic photoautotrophs. The review focuses on the current and future applications of biological processes for biogas desulfurization and provides insights into their mechanism and main factors influencing their performance. The advantages, drawbacks, limitations, and technical improvements of the biotechnological applications currently based on chemolithoautotrophic organisms are covered extensively. Recent advances, sustainability and economical aspects of biological biogas desulfurization are also discussed. Anoxygenic photoautotrophic-bacteria-based photobioreactors were herein identified as useful tools to improve the sustainability and safety of biological biogas desulfurization. The review addresses gaps in the existing studies concerning the selection of the most suitable desulfurization techniques, their benefits and consequences. The research is useful for all stakeholders involved in the management and optimization of biogas and its findings are directly applicable in the development of new sustainable technologies for biogas upgrading processes on waste treatment plants.

Unraveling microbial community by next-generation sequencing in living membrane bioreactors for wastewater treatment.

This study delves into the microbial community complexity and its role in self-forming dynamic membrane (SFDM) systems, designed to remove nutrients and pollutants from wastewater, by means of the analysis of Next-Generation Sequencing (NGS) data. In these systems, microorganisms are naturally incorporated into the SFDM layer, which acts as a biological and physical filter. The microorganisms present in an innovative and highly efficient aerobic, electrochemically enhanced, encapsulated SFDM bioreactor were studied to elucidate the nature of the dominant microbial communities present in sludge and in encapsulated SFDM, patented as living membrane® (LM) of the experimental setup. The results were compared to those obtained from the microbial communities found in similar experimental reactors without an applied electric field. The data gathered from the NGS microbiome profiling showed that the microbial consortia found in the experimental systems are comprised of archaeal, bacterial, and fungal communities. However, the distribution of the microbial communities found in e-LMBR and LMBR had significant differences. The results showed that the presence of an intermittently applied electric field in e-LMBR promotes the growth of some types of microorganisms (mainly electroactive microorganisms) responsible for the highly efficient treatment of the wastewater and for the mitigation of the membrane fouling found for those bioreactors.

XANES/EXAFS and quantum chemical study of the speciation of arsenic in the condensate formed in landfill gas processing: Evidence of the dominance of As-S species.

The XANES/EXAFS data and quantum chemical simulations presented in this study demonstrate several features of the chemistry of arsenic compounds found in the condensates and solids generated in landfill gas (LFG) processing carried out for renewable natural gas (RNG) production. The XANES data show the decrease in the position of the absorption edge of As atoms, similar to that characteristic for sulfur-containing As solutes and solids. The EXAFS data show that the As-O and As-S distances in these matrixes are similar to those in thioarsenates. Quantum-chemical calculations demonstrated the close agreement between the experimental and modeled As-S and As-O distances determined for a range of methylated and thiolated arsenic solutes. These calculations also showed that the increase of the number of the As-S bonds in the coordination shell of arsenic is accompanied by a consistent decrease of the charges of As atoms. This decrease is correlated with the number of the As-S bonds, in agreement with the trend observed in the XANES data. These results provide insight into the intrinsic chemistry and reactivity of As species present in LFG matrixes; they may be helpful for the development of treatment methods to control arsenic in these systems.

Changes of dissolved organic matter fractions and formation of oxidation byproducts during electrochemical treatment of landfill leachates: Development of spectroscopic indicators for process optimization.

Electrochemical oxidation (EO) is an attractive option for treatment of dissolved organic matter (DOM) in landfill leachate but concerns remain over the energy efficiency and formation of oxidation byproducts ClO3- and ClO4-. In this study, EO treatment of landfill leachates was carried out using representative active and nonactive anode materials, cell configurations and current densities. Size exclusion chromatograms coupled with 2D synchronous and asynchronous correlation analysis showed that the sensitivity of DOM fractions to EO degradation was dependent on the anode material. The nonactive boron-doped diamond (BDD) anode demonstrated the best performance for DOM oxidation. The humic acid-like fraction (HA, 2.5-20 kDa) predominated the visible absorbance of landfill leachates at λ ≥400 nm, and it generally had the highest reaction rates except the occurrence of the pH-induced denaturation and precipitation of the proteinaceous biopolymer fraction (BP, >20 kDa). During the EO treatment of landfill leachate with BDD anode, the UV absorbance spectra of landfill leachates at wavelengths <400 nm were affected by the formation of free chlorine. Instead, the decrease of Abs420 was found to be a good indicator of the shift of the oxidation from predominantly HA fraction to the proteinaceous BP fraction. The behavior of the Abs420 parameter was also indicative of the transition from the energy-efficient oxidation of DOM to the dominance of side reactions of chlorine evolution and the subsequent formation of ClO3- and ClO4-. These findings suggest that the EO treatment of landfill leachate can be optimized by adjusting the current density with feedback signals from the online monitoring of Abs420, to achieve a trade-off between degradation of DOM and control of ClO3- and ClO4-.

Transformation of macrolide antibiotics during chlorination process: Kinetics, degradation products, and comprehensive toxicity evaluation.

Antibiotics are ubiquitous in wastewater and surface water and their presence is of grave concern. Chlorination, an important disinfection process used in wastewater treatment plants and waterworks, causes antibiotics to be degraded. However, interactions of antibiotics with chlorine result in the generation of multiple transformation products (TPs). TPs may be more toxic than the parent compounds, but their structures, yields and ecotoxicity remain to be ascertained in most cases. This study examined the degradation by chlorine of two typical macrolide (MLs) antibiotics, erythromycin (ERY) and roxithromycin (ROX), and identified the TPs formed as a result of ERY and ROX chlorination. The ecotoxicity of ERY, ROX and their TPs was evaluated using a combination of bioassay and ECOSAR prediction. The degradation of ERY and ROX followed pseudo-first-order kinetic at the molar ratio of FAC to MLs of 10:1, and the degradation kinetic rate depends on pH values. Six TPs of ERY including three chlorinated TPs, and six TPs of ROX including two chlorinated TPs were identified. The tertiary N of the desosamine moiety of ERY and ROX was determined to be the main reactive site. Demethylation and chlorine substitution at the reactive site are the main degradation pathways of ERY and ROX. ECOSAR results showed that the chlorinated byproducts of ERY TP578, TP542 and TP528, and the reduced hydroxylation products of ROX TP851 exhibited higher ecotoxicity than their parent compounds. However, algae growth inhibition assays indicated that the overall ecotoxicity of the chlorinated ERY or ROX mixture was lower than that of ERY or ROX prior to chlorination. This may be attributed to the removal of the parent compound and lower yields of toxic substances. While the yields of the toxic TPs may be low, their accumulation and combined effects of the TPs and other co-occurring pollutants should be examined further.

New Insights into the Role of Nitrite in the Degradation of Tetrabromobisphenol S by Sulfate Radical Oxidation.

Tetrabromobisphenol S (TBBPS) is a brominated flame retardant and a contaminant of emerging concern. Several studies found that sulfate radical (SO4•-) oxidation is effective to degrade TBBPS. Here, we demonstrate that the presence of nitrite (NO2-) at environmentally relevant levels causes dramatic changes in the kinetics and pathways of TBBPS degradation by SO4•-. Initially, NO2- suppresses the reaction by competing with TBBPS for SO4•-. At the same time, SO4•- oxidizes NO2- to form nitrogen dioxide radicals (NO2•), which actively react with some key TBBPS degradation intermediates, thus greatly altering the transformation pathway. As a result, 2,6-dibromo-4-nitrophenol (DBNP) becomes the primary TBBPS product. As TBBPS undergoes degradation, the released bromide (Br-) is oxidized by SO4•- to form bromine radicals and free bromine. These reactive bromine species immediately combine with NO2• or NO2- to form nitryl bromide (BrNO2) that in turn attacks the parent TBBPS, resulting in its accelerated degradation and increased formation of toxic nitrophenolic byproducts. These results show that nitryl halides (e.g., BrNO2 or ClNO2) are likely formed yet inadequately recognized when SO4•- is applied to remediate halogenated pollutants in the subsurface environment where NO2- is ubiquitously found. These insights further underscore the potential risks of the application of SO4•- oxidation for the remediation of halogenated compounds in realistic environmental conditions.

Comparison of the formation of aldehydes and carboxylic acids in ozonated and electrochemically treated surface water.

This study compared effects of conventional ozonation and electrochemical oxidation (EO) on the formation of aldehydes and aliphatic carboxylic acids produced via the oxidation of natural organic matter (NOM) present in a low-mineralized surface water with a relatively low NOM concentration. Conventional ozonation and EO were effective in degrading the aromatic moiety of NOM characterized by the absorbance at 254 nm. Yields of aliphatic carboxylic acids in the ozone treated water were dominated by formate, acetate and oxalate, while no acetate was observed in the case of EO treatment. The speciation of aldehydes was similar in the case of ozonation and EO treatment, but the aldehydes yields were notably higher for ozonation. The presence of the elevated carbonate concentration moderated the changes in disinfection by-products (DBPs) concentration in the EO treated water due to the interception of ∙OH by HCO3-, while it did not affect ozonation treatment. This study allows gaining more insights into the nature of processes characteristic and optimization of disinfections based on ozonation and EO methods.

Differentiation of Pathways of Nitrated Byproduct Formation from Ammonium and Nitrite During Sulfate Radical Oxidation.

Recent studies found that both nitrite (NO2-) and ammonium (NH4+) lead to nitrophenolic byproducts in SO4•- oxidation processes, during which NO2• generated through the oxidation of the inorganic nitrogen by SO4•- is the key nitrating agent. This study demonstrates that the formation of phenoxy radicals to which NO2• can be incorporated immediately is another governing factor. Two types of sites having distinct reactivities in natural organic matter (NOM) molecules can be transformed to phenoxy radicals upon SO4•- oxidation. Fast sites associated with phenolic functionalities are primarily targeted in the reaction sequence involving NO2-, because both are preferentially oxidized. Following the depletion of NO2-, NH4+ becomes the main precursor of NO2• that interacts with slow sites associated with the carboxylic functionalities. Experimental data show that the formation of total organic nitrogen in 24 h reached 6.28 µM during SO4•- oxidation of NOM (4.96 mg/L organic carbon) in the presence of both NO2- (0.1 mM) and NH4+ (1.0 mM), while the sum of those formed in the presence of each alone was only 3.52 µM. Results of this study provide further insights into the mechanisms of nitrated byproduct formation when SO4•- is applied for environmental remediation.

Active-chlorine-mediated oxidation of 5-fluorouracil on a hierarchically ordered macroporous RuO2 electrode.

A hierarchically ordered macroporous RuO2 electrode (HOM-RuO2) was fabricated to enhance in situ active chlorine production in an electrochemical system intended for treatment of pharmaceutical active compounds (PhACs). The unique structure of HOM-RuO2 resulted in a decrease of the chlorine evolution potential, a large electro-active area available for in situ conversion of Cl- to active chlorine, and hence improved the active chlorine production by 40%. 5-Fluorouracil (5-FU) was used as a target pollutant to explore the performance of the HOM-RuO2 for PhACs degradation based on the in situ generated active chlorine. The results showed that the reaction rate of active-chlorine-mediated oxidation of 5-FU produced using the HOM-RuO2 was 18.4 times higher than that in the case of hydroxyl radicals (OH)-initiated oxidation using a PbO2 electrode at 30 mA cm-2. The effects of current density and initial solution pH on the 5-FU removal were investigated. The mechanism of 5-FU degradation was proposed taking into accounts both active chlorine production, and change of the speciation of 5-FU caused by pH variations. The dominant degradation products observed for the degradation of 5-FU using the HOM-RuO2 were lactic acid, propanol, acetic acid, urea and other small molecules, but no chlorinated products were detected. These study demonstrates the promise of the HOM-RuO2-based electrochemical systems for the active-chlorine-mediated treatment of recalcitrant pharmaceuticals found in wastewater.

Removal of dimethylarsinic acid (DMA) in the Fe/C system: roles of Fe(II) release, DMA/Fe(II) and DMA/Fe(III) complexation.

Methylated arsenic species are ubiquitous in the environment and resistant to removal by conventional treatment technologies. This study addressed this challenge based on the examination of the removal of dimethylarsinic acid (DMA) in a system that combines zerovalent iron (ZVI) and powdered activated carbon (PAC). The removal of DMA in the ZVI/PAC system was compared to that by coagulation, adsorption, electrochemical and Fenton oxidations, and other conventional methods. While only the electrochemical oxidation using a PbO2/Sb-SnO2/Ti anode allowed removing up to 60% DMA at several hours-long treatment times, the removal of DMA in the ZVI/PAC system containing 10 g/L ZVI and 2.5 g/L PAC with an initial pH of 2.0 was 95% for a 30 min reaction time. Specific roles of PAC, ZVI and its oxidation products in DMA removal were examined based on the spectroscopic data and quantum chemical modeling for the DMA/Fe(II) and DMA/Fe(III) systems. These methods demonstrated the formation of moderately strong DMA/Fe(II) and DMA/Fe(III) complexation. These results and relevant kinetic data were interpreted to indicate that the removal of DMA is governed by the rapid generation of Fe2+ ions released as a result of accelerated ZVI corrosion in the galvanic ZVI/PAC microcells and ensuing formation of DMA/ Fe2+ complexes that are readily adsorbed by PAC.

Advances in virus detection methods for wastewater-based epidemiological applications.

Wastewater-based epidemiology (WBE) is a powerful tool that has the potential to reveal the extent of an ongoing disease outbreak or to predict an emerging one. Recent studies have shown that SARS-CoV-2 concentration in wastewater may be correlated with the number of COVID-19 cases in the corresponding population. Most of the recent studies and applications of wastewater-based surveillance of SARS-CoV-2 applied the "gold standard" real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR) detection method. However, this method also has its limitations. The paper aimed to present recent improvements and applications of the PCR-based methods for SARS-CoV-2 monitoring in wastewater. Furthermore, it aimed to review alternative methods utilized and/or proposed for the detection of the virus in wastewater matrices. From the review, it was found that several studies have investigated the use of reverse-transcription digital polymerase reaction (RT-dPCR), which was generally shown to have a lower limit of detection (LOD) over the RT-qPCR. Aside from this, non-PCR-based and non-RNA based methods have also been explored for the detection of SARS-CoV-2 in wastewater, with detailed attention given to the detection of SARS-CoV-2 proteins. The potential methods for protein detection include mass spectrometry, the use of immunosensors, and nanotechnological applications. In addition, the review of recent studies also revealed two types of emerging methods related to the detection of SARS-CoV-2 in wastewater: i) capsid-integrity assays to infer about the infectivity of SARS-CoV-2 present in wastewater, and ii) alternative methods for detection of SARS-CoV-2 variants of concern (VOCs) in wastewater. The recent studies on proposed methods of SARS-CoV-2 detection in wastewater have considered improving this approach in one or more of the following aspects: rapidity, simplicity, cost, sensitivity, and specificity. However, further studies are needed in order to realize the full application of these methods for WBE in the field.

Effect of chlorination on the characteristics of effluent organic matter and the phototransformation of sulfamethoxazole in secondary wastewater.

Chlorination is the most common disinfection technology used to treat wastewater effluent discharged into receiving aquatic environments. Effluent organic matter (EfOM) abundant in wastewater is a well-known photosensitizer and it greatly affects phototransformation of antibiotics in water. However, effects of chlorination on the characteristics and photochemical properties of EfOM have not been studied in sufficient detail. This paper investigated effects of chlorination on the characteristics of EfOM, and its impact on the phototransformation of sulfamethoxazole (SMX). Correlations between the EfOM characteristics and steady-state concentrations of reactive intermediates (RI) formed in the system were established. Chlorination was shown to preferentially remove the aromatic protein-like substances in EfOM, and the incorporation of chlorine into followed by the cleavage of the aromatic rings in EfOM molecules led to the formation of low molecular aliphatic organic matter. Both unaltered and chlorinated EfOM promoted the photodegradation of SMX whose rate constant in the wastewater was 1.32-1.65 times higher than that in pH 8 phosphate buffer. However, the rate of SMX photodegradation decreased at higher chlorination concentrations. The photodegradation of SMX was found to proceed through direct photolysis and oxidation by the RIs generated from EfOM and the self-sensitization of SMX. The steady-state concentrations of ·OH, 1O2 and 3EfOM* were 2.15-5.50 × 10-16, 0.42-1.51 × 10-13, and 2.54-5.82 × 10-14 M in unaltered and chlorinated wastewater. The steady-state concentrations of ·OH were well correlated with the removal of the fluorescence regional integration (ΔFRI) for humic-like and soluble microbial products (SMPs), while the photodegradation rate constant of SMX and the steady-state concentration of 1O2 and 3EfOM* showed good correlations with ΔFRI for tryptophan and fulvic-like substances. Six transformation products (TPs) of SMX were identified. These findings provide new insights into the photochemical properties of chlorinated EfOM in the aquatic environments and its roles in the degradation of antibiotics and other trace-level pharmaceuticals.

Interactions between the antibiotic tetracycline and humic acid: Examination of the binding sites, and effects of complexation on the oxidation of tetracycline.

The binding between dissolved organic matter (DOM) and micro-pollutants (MPs) results in significant impacts on their migration, transformation and degradation. However, the role of the DOM/MP binding on their oxidative transformation remains poorly studied. The binding of MPs by DOM, in combination with DOM's roles as a photosensitizer and/or a competitor for free radicals, needs to be considered in the context of understanding the DOM's impacts on the oxidative degradation of MPs. This study aims to explore this aspect of DOM/MP interactions based on the quantitation of humic acid (HA) and tetracycline (TET) complexation and its role in TET removal. This study also compared the degradation of free TET versus that bound in HA-TET complexes in different oxidation processes. Fourier transform infrared (FTIR) data show that the carboxyl and phenolic hydroxyl groups in HA are the main binding sites of TET, while nuclear magnetic resonance (NMR) analysis shows the binding of TET engages its -N(CH3)2 groups, and two-dimensional correlation spectroscopy (2D-COS) data show that the carboxyl groups in DOM are sensitive than phenolic groups in the binding of TET. The difference between the degradation rates (Δkobs) of the free and bound TET decreased with the increase of ionic strength using sodium nitrate, but increased with the introduction of Ca2+ and Mg2+ due to the formation of TET-Ca2+/Mg2+ complexes. Quenching experiments showed that the free radicals (•OH and •SO4-), PMS oxidant and UV light were the main contributors to the TET degradation in UV/PS, UV/PMS and UV/H2O2 processes, respectively. In-situ fluorescence time scanning and differential absorbance spectra showed that free TET was preferentially oxidized over the bound TET in all the tested treatments except UV/PS. These results provide new insights into the role of DOM/MP complexation in the degradation of MPs in natural and engineered systems.

Solid-phase excitation-emission matrix spectroscopy for chemical analysis of combustion aerosols.

Exposure to ultrafine combustion aerosols such as particulate matter (PM) from residential woodburning, forest fires, cigarette smoke, and traffic emission have been linked to adverse health outcomes. Excitation-emission matrix (EEM) spectroscopy presents a sensitive and cost-effective alternative for analysis of PM organic fraction. However, as with other analytical chemistry methods, the miniaturization is hindered by a solvent extraction step and a need for benchtop instrumentation. We present a methodology for collecting and in-situ analysis of airborne nanoparticles that eliminates labor-intensive sample preparation and miniaturizes the detection platform. Nanoparticles are electrostatically collected onto a transparent substrate coated with solid-phase (SP) solvent-polydimethylsiloxane (PDMS). The PM organic fraction is extracted into PDMS and analyzed in-situ, thus avoiding liquid-phase extraction. In the SP-EEM analysis, we evaluated external and internal excitation schemes. Internal excitation shows the lowest scattering interference but leads to signal masking from PDMS fluorescence for λ<250nm. The external excitation EEM spectra are dependent on the excitation light incident angle; ranges of 30-40° and 55-65° show the best results. SP-EEM spectra of woodsmoke and cigarette smoke samples are in good agreement with the EEM spectra of liquid-phase extracts. The SP-EEM technique can be used to develop wearable sensors for exposure assessments and environmental monitoring.

Coronavirus in water media: Analysis, fate, disinfection and epidemiological applications.

Considerable attention has been recently given to possible transmission of SARS-CoV-2 via water media. This review addresses this issue and examines the fate of coronaviruses (CoVs) in water systems, with particular attention to the recently available information on the novel SARS-CoV-2. The methods for the determination of viable virus particles and quantification of CoVs and, in particular, of SARS-CoV-2 in water and wastewater are discussed with particular regard to the methods of concentration and to the emerging methods of detection. The analysis of the environmental stability of CoVs, with particular regard of SARS-CoV-2, and the efficacy of the disinfection methods are extensively reviewed as well. This information provides a broad view of the state-of-the-art for researchers involved in the investigation of CoVs in aquatic systems, and poses the basis for further analyses and discussions on the risk associated to the presence of SARS-CoV-2 in water media. The examined data indicates that detection of the virus in wastewater and natural water bodies provides a potentially powerful tool for quantitative microbiological risk assessment (QMRA) and for wastewater-based epidemiology (WBE) for the evaluation of the level of circulation of the virus in a population. Assays of the viable virions in water media provide information on the integrity, capability of replication (in suitable host species) and on the potential infectivity. Challenges and critical issues relevant to the detection of coronaviruses in different water matrixes with both direct and surrogate methods as well as in the implementation of epidemiological tools are presented and critically discussed.