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.

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.

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.

Excitation Emission Matrix Fluorescence Spectroscopy for Combustion Generated Particulate Matter Source Identification.

The inhalation of particulate matter (PM) is a significant health risk associated with reduced life expectancy due to increased cardio-pulmonary disease and exacerbation of respiratory diseases such as asthma and pneumonia. PM originates from natural and anthropogenic sources including combustion engines, cigarettes, agricultural burning, and forest fires. Identifying the source of PM can inform effective mitigation strategies and policies, but this is difficult to do using current techniques. Here we present a method for identifying PM source using excitation emission matrix (EEM) fluorescence spectroscopy and a machine learning algorithm. We collected combustion generated PM2.5 from wood burning, diesel exhaust, and cigarettes using filters. Filters were weighted to determine mass concentration followed by extraction into cyclohexane and analysis by EEM fluorescence spectroscopy. Spectra obtained from each source served as training data for a convolutional neural network (CNN) used for source identification in mixed samples. This method can predict the presence or absence of the three laboratory sources with an overall accuracy of 89% when the threshold for classifying a source as present is 1.1 µg/m3 in air over a 24-hour sampling time. The limit of detection for cigarette, diesel and wood are 0.7, 2.6, 0.9 µg/m3, respectively, in air assuming a 24-hour sampling time at an air sampling rate of 1.8 liters per minute. We applied the CNN algorithm developed using the laboratory training data to a small set of field samples and found the algorithm was effective in some cases but would require a training data set containing more samples to be more broadly applicable.

Monitoring the Behavior of Emerging Contaminants in Wastewater-Impacted Rivers Based on the Use of Fluorescence Excitation Emission Matrixes (EEM).

This study investigated the applicability of fluorescence indexes based on the interpretation of excitation emission matrices (EEMs) by PARAFAC analysis and by selecting fluorescence intensities at a priori defined excitation/emission pairs as surrogates for monitoring the behavior of emerging organic compounds (EOCs) in two catchment basins impacted by wastewater discharges. Relevant EOC and EEM data were obtained for a 90 km stretch of the Simeto River, the main river in Sicily, and the smaller San Leonardo River, which was investigated for a 17 km stretch. The use of fluorescence indexes developed by these two different approaches resulted in similar observations. Changes of the fluorescence indexes that correspond to a group of humic-like fluorescing species were determined to be highly correlated with the concentrations of recalcitrant contaminants such as sucralose, sulfamethoxazole and carbamazepine, which are typical wastewater markers in river water. Changes of the fluorescence indexes related to tyrosine-like substances were well correlated with the concentrations of ibuprofen and caffeine, anthropogenic indicators of untreated wastewater discharges. Chemical oxygen demand and dissolved organic carbon concentrations were correlated with humic-like fluorescence indexes. The observed correlations were site-specific and characterized by different regression parameters for every collection event. Caffeine and carbamazepine showed correlations with florescence indexes in the San Leonardo River and in the alluvial plain stretch of the Simeto River, whereas sucralose, sulfamethoxazole and ibuprofen have always been well correlated in all the investigated river stretches. However, when data of different collection events from river stretches where correlations were observed were combined, good linear correlations were obtained for data sets generated via the normalization of the measured concentrations by the average value for the corresponding collection event. These results show that fluorescence based indexes can be used to monitor the behavior of some trace organic contaminants in wastewater impacted rivers and to track wastewater discharges in streams and rivers.

Ternary Model of the Speciation of I-/Br-/Cl-Trihalomethanes Formed in Chloraminated Surface Waters.

This study examined the effects of the iodide concentration and pH on yields and speciation of the entire group of 10 species of iodine-, bromine-, and chlorine-containing trihalomethanes (THMs) formed at pH values from 6.5 to 8.5 in chloraminated surface waters in the presence of bromide and iodide. Pathways of iodine, bromine, and chlorine incorporation in the active sites in dissolved organic matter (DOM) were examined on the basis of a ternary halogenation/THM speciation model. The model assumed the occurrence of sequential three-step halogenation of the active site and competition of iodine, bromine, and chlorine species at each node of the halogenation sequence. A comparison of experimentally measured and modeled speciation coefficients and also iodine and bromine incorporation factors calculated for 10 THM species showed that the developed approach was sufficient to closely model the observed trends. Interpretation of preferred iodine incorporation pathways associated with the generation of THMs in all examined conditions showed that the susceptibility of the halogenated intermediates to iodine incorporation increases rapidly with the number of iodine atoms that have already been incorporated into the reaction site. In contrast, the incorporation of bromine and chlorine atoms in the intermediates involved in the generation of THMs makes them largely inactive in iodine incorporation reactions. The presented approach allows for a further understanding of the mechanisms of DOM/halogen interactions and prediction of the speciation of THMs formed at varying pH values, iodide concentrations, and other system conditions.

Effects of ionic strength on the chromophores of dissolved organic matter.

This study examined effects of variations of the ionic strength (IS) on the absorbance of dissolved organic matter (DOM). The measurements performed for DOM of allochthonous (Suwannee River humic and fulvic acids, SRHA and SRFA) and autochthonous (Pony Lake fulvic acid, PLFA) origin showed that increases of IS (which was controlled by additions of sodium perchlorate) from 0.001 to 0.3 mol/L were accompanied by increases of the absorbance of DOM. The extent of the increase of DOM absorbance observed at increasing IS was consistently greater at higher pH values, and it followed the order of PLFA < SRFA < SRHA. The absolute values of the spectral slopes of the log-processed absorbance spectra of DOM calculated for a 350 to 400 nm wavelength range decreased proportionally to the logarithm of IS values. This result was hypothesized to be indicative of the deprotonation of the DOM chromophores at increasing IS values, which was supported by model calculations showing that values of the spectral slopes were nearly linearly correlated with the extent of IS-induced deprotonation of the operationally defined phenolic groups in DOM.

In-Situ Investigation of Interactions between Magnesium Ion and Natural Organic Matter.

Natural organic matter (NOM) generated in all niches of the environment constitutes a large fraction of the global pool of organic carbon while magnesium is one of the most abundant elements that has multiple roles in both biotic and abiotic processes. Although interactions between Mg(2+) and NOM have been recognized to affect many environmental processes, little is understood about relevant mechanisms and equilibria. This study addressed this deficiency and quantified Mg(2+)-NOM interactions using differential absorbance spectroscopy (DAS) in combination with the NICA-Donnan speciation model. DAS data were obtained for varying total Mg concentrations, pHs from 5.0 to 11.0 and ionic strengths from 0.001 to 0.3 mol L(-1). DAS results demonstrated the existence of strong interactions between magnesium and NOM at all examined conditions and demonstrated that the binding of Mg(2+) by NOM was accompanied by the replacement of protons in the protonation-active phenolic and carboxylic groups. The slope of the log-transformed absorbance spectra of NOM in the range of wavelength 350-400 nm was found to be indicative of the extent of Mg(2+)-NOM binding. The differential and absolute values of the spectral slopes were strongly correlated with the amount of NOM-bound Mg(2+) ions and with the concentrations of NOM-bound protons.

Rotating Ring-Disk Electrode and Quantum-Chemical Study of the Electrochemical Reduction of Monoiodoacetic Acid and Iodoform.

This study examined the electrochemical (EC) reduction of monoiodoacetic acid (MIAA) and iodoform (CHI3), which are typical iodine-containing disinfection byproducts (I-DBPs). Experiments carried out using the method of a rotating ring-disk electrode (RRDE) with a gold working electrode showed that the reduction of CHI3 and MIAA is diffusion-controlled. The MIAA diffusion coefficient was determined to be (1.86 ± 0.24)·10(-5) cm(2) s(-1). The yield of the iodide ion formed as a result of MIAA or CHI3 reduction was affected by the presence of dissolved organic matter (DOM) and resorcinol. Increasing concentrations of DOM or resorcinol did not affect the EC reduction of the examined I-DBPs, but the formation of iodide was suppressed. This indicated that free iodine, ·I, was formed as a result of the first step in the EC reduction of MIAA and CHI3. This also indicated that the pathway of the EC reduction of MIAA and CHI3 was different from that typical for the reduction of Br- and Cl-containing DBPs, in which case Br(-) or Cl(-) tend to be formed as a result of the electron transfer. Quantum-chemical (QC) calculations confirmed the thermodynamic likelihood of and possible preference to the formation of free iodine species as a result of the EC reduction of MIAA, CHI3, and other I-DBPs.

Comparative examination of effects of binding of different metals on chromophores of dissolved organic matter.

This study quantified the binding of dissolved organic matter (DOM) from Suwannee River with nine metals, Ca(II), Mg(II), Fe(III), Al(III), Cu(II), Cd(II), Cr(III), Eu(III), and Th(IV), using a differential absorbance approach. The differential spectra of DOM were closely fitted with six Gaussian bands that were present for all of the metals at varying pH values. Their maxima were located at ca. 200, 240, 276, 316, 385, and 547 nm (denoted as A0, A1, A2, A3, A4, and A5, respectively). The relative contributions and signs of the Gaussian bands were metal-specific and correlated to some degree with the covalent-bonding index of the ions and applicable complexation constants of the NICA-Donnan model. The intensity of band A4 was linearly proportional to the concentration of DOM-complexed metal, although these correlations formed two groups with different slopes, reflecting the nature of DOM-metal interactions. The results demonstrate that differential spectra yield results indicative of the nature and extent of metal and DOM interactions.

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.

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.

Micro(nano)plastics from synthetic oligomers persisting in Mediterranean seawater: Comprehensive NMR analysis, concerns and origins.

The presence in seawater of low-molecular-weight polyethylene (PE) and polydimethylsiloxane (PDMS), synthetic polymers with high chemical resistance, has been demonstrated in this study for the first time by developing a novel methodology for their recovery and quantification from surface seawater. These synthetic polymer debris (SPD) with very low molecular weights and sizes in the nano- and micro-metre range have escaped conventional analytical methods. SPD have been easily recovered from water samples (2 L) through filtration with a nitrocellulose membrane filter with a pore size of 0.45 µm. Dissolving the filter in acetone allowed the isolation of the particulates by centrifugation followed by drying. The isolated SPD were analysed by 1H nuclear magnetic resonance spectroscopy (1H NMR), identifying PE and PDMS. These polymers are thus persisting on seawater because of their low density and the ponderal concentrations were quantified in mg/m3. This method was used in an actual case study in which 120 surface seawater samples were collected during two sampling campaigns in the Mediterranean Sea (from the Gulf of Salerno to the Gulf of Policastro in South Italy). The developed analytical protocol allowed achieving unprecedented simplicity, rapidity and sensitivity. The 1H and 13C NMR structural analysis of the PE debris indicates the presence of oxidised polymer chains with very low molecular weights. Additionally, the origin of those low molecular weight polymers was investigated by analysing influents and effluents from a wastewater treatment plant (WWTP) in Salerno as a hot spot for the release of SPD: the analysis indicates the presence of low molecular weight polymers compatible with wax-PE, widely used for coating applications, food industry, cosmetics and detergents. Moreover, the origin of PDMS debris found in surface seawater can be ascribed to silicone-based antifoamers and emulsifiers.

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.

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.

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-.

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.

Formation of Pb(III) intermediates in the electrochemically controlled Pb(II)/PbO2 system.

The formation of lead dioxide PbO(2), an important corrosion product in drinking water distribution systems with lead-bearing plumbing materials, has been hypothesized to involve Pb(III) intermediates, but their nature and formation mechanisms remain unexplored. This study employed the electrochemical (EC) method of rotating ring disk electrode (RRDE) and quantum chemical (QC) simulations to examine the generation of intermediates produced during the oxidation of Pb(II) to PbO(2). RRDE data demonstrate that PbO(2) deposition and reduction involves at least two intermediates. One of them is a soluble Pb(III) species that undergoes further transformations to yield immobilized PbO(2) nanoparticles. The formation of this intermediate in EC system is mediated by hydroxyl radicals (OH(•)), as was evidenced by the suppression of intermediates formation in the presence of the OH(•) scavenger para-chlorobenzoic acid. QC simulations confirmed that the oxidation of Pb(II) by OH(•) proceeds via Pb(III) species. These results show that Pb(III) intermediates play an important role in the reactions determining transitions between Pb(II) and Pb(IV) species and could impact lead release in drinking water.

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.