FT-ICR MS Spectral Improvement of Dissolved Organic Matter by the Absorption Mode: A Comparison of the Electrospray Ionization in Positive-Ion and Negative-Ion Modes.

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in the absorption mode has a superior performance over the conventional magnitude mode. However, this improved performance for the analysis of dissolved organic matter (DOM) in negative-ion and positive-ion modes of electrospray ionization [ESI(-) and ESI(+), respectively] remains unknown. This study systemically compared the improved performance by the absorption mode for DOM FT-ICR MS spectra acquired with the low-field and high-field magnet instruments between two charge modes. The absorption mode enhanced the resolution and signal-to-noise ratio values of DOM peaks with factors of 1.88-1.94 and 1.60-1.72, respectively. The significantly higher improvement of mass resolution for the ESI(+) mode than that for the ESI(-) mode could resolve the extensive occurrence of mass doublets in the ESI(+) mode, yielding some formulas exclusively identified in the ESI(+) mode. The findings of this study have systemically demonstrated the superiority of the absorption mode in improving the spectra quality during the routine FT-ICR MS postdata analysis and highlighted its great potential in characterizing the molecular composition of DOM using the FT-ICR MS technique in both ESI(-) and ESI(+) modes.

Interpretable Machine Learning and Reactomics Assisted Isotopically Labeled FT-ICR-MS for Exploring the Reactivity and Transformation of Natural Organic Matter during Ultraviolet Photolysis.

Isotopically labeled FT-ICR-MS combined with multiple post-analyses, including interpretable machine learning (IML) and a paired mass distance (PMD) network, was employed to unravel the reactivity and transformation of natural organic matter (NOM) during ultraviolet (UV) irradiation. FT-ICR-MS analysis was used to assign formulas, which were classified on the basis of their molecular compositions and structural categories. Isotope (deuterium, D) labeling was utilized to unequivocally determine the photochemical products and examine the development of OD radical-mediated NOM transformation. With regard to the reactive molecular formulas, CHOS formulas exhibited the highest reactivity (86.5% of precursors disappeared) followed by CHON (53.4%) and CHO (24.6%) formulas. With regard to structural categories, the degree of reactivity decreased in the following order: tannins > condensed aromatics > lignin/CRAMs. The IML algorithm demonstrated that the crucial features governing the reactivity of formulas were the molecular weight, DBE-O, NOSC, and the presence of heteroatoms (i.e., N and S), suggesting that the large and unsaturated compounds containing S and N are more prone to photodegradation. The reactomics approach using the PMD network further indicated that 11 specific molecular formulas in the CHOS and CHO class served as hubs, implying a higher photoreactivity and participation in a range of transformations. The isotope labeling analyses also found that, among the reactions observed, hydroxylation (i.e., +OD) is dominant for lignin/CRAMs and condensed aromatics, and formulas containing ≤10 D atoms were developed. Overall, this study, by adopting rigorous and interpretable techniques, could provide in-depth insights into the molecular-level dynamics of NOM under UV irradiation.

Pontederia crassipes utilization for dual phytoremediation and adsorption in greywater treatment: a techno-economic and sustainable approach.

While phytoremediation has been widely employed for greywater treatment, this system suffers from the transfer of considerable amounts of surfactants to the aquatic environment through partially treated effluent and/or exhausted plant disposal. Hence, this study focuses on greywater phytoremediation followed by recycling the spent plant for preparing an adsorbent material used as post-treatment. P. crassipes was used to operate a phytoremediation unit under 23 °C, 60% relative humidity, plant density (5-30 g/L), dilution (0-50%), pH (4-10), and retention time (3-15 days). The optimum condition was 12.7 g/L density, 34.0% dilution, pH 8.4, and 13 days, giving chemical oxygen demand (COD), surfactant, and NH4-N removal efficiencies of 94.62%, 90.45%, and 88.09%, respectively. The exhausted plant was then thermally treated at 550 °C and 40 min to obtain biochar used as adsorbent to treat the phytoremediation effluent. The optimum adsorption process was biochar dosage of 1.51 g/L, pH of 2.1, and 137 min, providing a surfactant removal efficiency of 92.56%. The final discharge of this phytoremediation/adsorption combined process contained 8.30 mg/L COD, 0.23 mg/L surfactant, and 0.94 mg/L NH4+-N. Interestingly, this approach could be economically feasible with a payback period of 6.5 years, 14 USD net present value, and 8.6% internal rate of return.

The research succeeded in treating greywater by phytoremediation followed by recycling the exhausted P. crassipes plant to prepare an adsorbent material used in the post-treatment phase, giving an economically feasible scenario with 6.5-year payback period.

Development of a Gaussian-Based Alignment Algorithm for the Ultrahigh-Resolution Mass Spectra of Dissolved Organic Matter.

The alignment of ultrahigh-resolution mass spectra (UHR-MS) is critical to inspect the presence of unique and common peaks across multiple UHR-MS spectra. However, few attempts have been conducted to develop an automated alignment method. In this study, a novel automated alignment algorithm, namely, FTMSCombine, that follows a Gaussian distribution of mass errors was developed and then integrated with existing FTMSCalibrate and TRFu algorithms to establish an open-source analysis platform, namely, FTMSAnalysis, for the UHR-MS analysis of the dissolved organic matter. The developed FTMSCombine was capable of automatically aligning peaks across different UHR-MS spectra by averaging the m/z values of each peak cluster, although the alignment should be restricted to Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) spectra collected by instruments under similar conditions. The FTMSCombine exhibited an insignificant difference in the reproducibility of chemical formulae but significantly higher mass accuracy than the ICBM-OCEAN. In addition to improving the overall mass accuracy of the whole UHR-MS dataset, the FTMSCombine could effectively exclude scatters or noise peaks using an optional rule that restricts peaks (continuously) detected in at least a certain number of spectra in the UHR-MS spectra dataset. The successfully established FTMSAnalysis (freely available in the Supporting Information of this study) is of great potential in automatically analyzing UHR-MS spectra for dissolved organic matter (DOM) and will largely facilitate the elucidation of DOM chemodivesity by UHR-MS techniques including FTICR-MS.

Complementary Elucidation of the Molecular Characteristics of Groundwater Dissolved Organic Matter Using Ultrahigh-Resolution Mass Spectrometry Coupled with Negative- and Positive-Ion Electrospray Ionization.

The formula assignment of the Fourier transform ion cyclotron resonance mass spectrometry coupled with positive-ion electrospray ionization [ESI(+)-FT-ICR MS] is challenging because of the extensive occurrence of adducts. However, there is a paucity of automated formula assignment methods for ESI(+)-FT-ICR MS spectra. The novel automated formula assignment algorithm for ESI(+)-FT-ICR MS spectra developed herein has been applied to elucidate the composition of dissolved organic matter (DOM) in groundwater during air-induced ferrous [Fe(II)] oxidation. The ESI(+)-FT-ICR MS spectra of groundwater DOM were profoundly impacted by [M + Na]+ adducts and, to a lesser extent, [M + K]+ adducts. Oxygen-poor and N-containing compounds were frequently detected when the FT-ICR MS was operated in the ESI(+) mode, while the components with higher carbon oxidation states were preferentially ionized in the negative-ion electrospray ionization [ESI(-)] mode. Values for the difference between double-bond equivalents and the number of oxygen atoms from -13 to 13 are proposed for the formula assignment of the ESI(+)-FT-ICR MS spectra of aquatic DOM. Furthermore, for the first time, the Fe(II)-mediated formation of highly toxic organic iodine species was reported in groundwater rich in Fe(II), iodide, and DOM. The results of this study not only shed light on the further algorithm development for comprehensive characterization of DOM by ESI(-)-FT-ICR MS and ESI(+)-FT-ICR MS but also highlight the importance of appropriate treatment of specific groundwater prior to use.

Effective decontamination of methylene blue from aqueous solutions using novel nano-magnetic biochar from green pea peels.

The conversion of agricultural waste into high-value carbon products has been an attractive area in waste management strategy. This study highlighted the synthesis and effectiveness of green pea peels (GPP), green pea biochar (GPBC), and nano-ferromagnetic green pea biochar (NFGPBC) by the ferrous/ferric co-precipitation synthesis method for eliminating cationic dyes molecules from solutions. The morphological, physicochemical, and structural properties of GPP, GPBC, and NFGPBC were approved by Scanning Electron Microscopy (SEM), Transmission Emission Microscopy (TEM), Energy Dispersive X-ray (EDX), Bruneau Emmett Teller (BET), Fourier Transform Infrared spectroscopy (FTIR), and X-ray Diffraction (XRD) techniques. Vibrating Sample Magnetometry (VSM) analysis confirmed the NFGPBC magnetization performance. The capacity of each adsorbent for methylene blue removal was evaluated at various parameters of material dosage (50-250 mg/150 mL), pH (2-12), initial concentration (50-250 mg/L), contact time (0-90 min) and temperature (20-60 °C). The three developed adsorbent materials GPP, GPBC, and NFGPBC, possessed reasonable BET surface areas of 0.6836, 372.54, and 147.88 m2g-1, and the corresponding monolayer adsorption capacities of 163.93, 217.40, and 175.44 mg/g, respectively. The superior performances of GPBC and NFGPBC were due to their increased surface area compared with the parent green pea peels (GPP). The results from adsorption kinetics studies of all prepared materials were pseudo-second-order and Elovich kinetics models. The thermodynamic parameters exhibited MB sorption's favorability, spontaneity, and endothermic nature. The NFGPBC material experienced Vander Waal forces, electrostatic interaction, hydrogen bonding, and hydrophobic interactions as predominant modes of the solid-liquid interaction. The regeneration, recycling, and reusability of the synthesized GPP, GPBC, and NFGPBC performed at five adsorption cycles revealed that NFGPBC demonstrated excellent cyclical performances attaining a minimum 8.9% loss in capacity due to paramagnetic properties. Thus, NFGPBC is a green, efficient, and eco-friendly material recommended for large-scale production and application in wastewater.

Development of an Internal Calibration Algorithm for Ultrahigh-Resolution Mass Spectra of Dissolved Organic Matter.

In order to obtain a spectrum with high mass accuracy, an internal calibration of Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is inevitable. This in turn is critical for subsequent data processing and is generally performed using the commercial instrument software DataAnalysis in the benchmark calibration mode. However, no methodological study has systemically addressed the automated internal calibration of FTICR-MS spectra for dissolved organic matter (DOM) from different sources such as terrestrial and aquatic environments. In this study, a new piecewise algorithm, FTMSCalibrate, was developed to automatically calibrate FTICR-MS spectra in both positive and negative ion modes. FTMSCalibrate was found to reproduce 91.7% ± 4.4% (referred to as the true positive ratio) of the chemical formulas obtained by calibration using manual DataAnalysis. In addition to significantly reducing the mass error, FTMSCalibrate is more accurate in terms of the molecular formula assignment for low m/z peaks than Formularity and MFAssignR. FTMSCalibrate was compatible with deprotonated ions for FTICR-MS spectra in the negative ion mode as well as protonated and adduct ions, including Na- and K-adducts, for FTICR-MS spectra in the positive ion mode. These results suggest that FTMSCalibrate publicly available herein is a robust alternative for the internal calibration of FTICR-MS spectra during postdata processing and will facilitate DOM analysis by FTICR-MS.

Formula Assignment Algorithm for Deuterium-Labeled Ultrahigh-Resolution Mass Spectrometry: Implications of the Formation Mechanism of Halogenated Disinfection Byproducts.

Ultrahigh-resolution mass spectrometry (UHR-MS) coupled with isotope labeling has attracted significant attention in elucidating the mechanisms of the transformation of dissolved organic matter (DOM). Herein, we developed a novel formula assignment algorithm based on deuterium (D)-labeled UHR-MS, namely, FTMSDeu, for the first time. This algorithm was employed to determine the precursor molecules of halogenated disinfection byproducts (Xn-DBPs) and to evaluate the relative contribution of electrophilic addition and substitution reactions in Xn-DBP formation according to the H/D exchange of DOM molecules. Further, tandem mass spectrometry with homologous-based network analysis was used to validate the formula assignment accuracy of FTMSDeu in the identification of iodinated disinfection byproducts. Electrophilic substitution accounted for 82-98, 71-89, and 43-45% of the formation for Cl-, Br-, and I-containing Xn-DBPs, respectively, indicating the dominant role of the electrophilic substitution in chlorinated disinfection byproducts with low Br and I concentrations. The absence of putative precursors in some Xn-DBPs also suggests that Xn-DBP formation includes secondary reactions (e.g., oxidation and hydrolysis) in addition to the electrophilic addition and/or substitution of halogens. These findings highlight the significance of isotopically labeled UHR-MS techniques in revealing the transformation of DOM in natural and engineered systems.

Novel S-scheme 2D/2D Bi4O5Br2 nanoplatelets/g-C3N5 heterojunctions with enhanced photocatalytic activity towards organic pollutants removal.

Removal of organic pollutants and pharma products in waste water using semiconductor photocatalysts has gained huge interest among recent days. However, low visible light absorption, recombination rate of charge carriers and less availability of reaction sites are still major obstacles for the photocatalysis process. Herein, an in situ-forming Bi4O5Br2 nanosheets decorated on the surface g-C3N5 were prepared via simple hydrothermal method under ambient temperature. The basic pH condition plays a vital role in growing for Bi4O5Br2 nanosheets. Various characterization studies such as TEM, SEM, PL and UV-DRS studies confirmed the formation of close contact between the Bi4O5Br2 and g-C3N5 nanosheets. The construction of Bi4O5Br2 nanoplatelets/g-C3N5 nanocomposite increases the surface-active sites and improving the separation efficiencies of excitons, which is greatly influenced in the degradation of ciprofloxacin and bisphenol-A pollutants. Meanwhile, the flow of electrons from the layered structured graphite carbon of g-C3N5 which enables excellent electrical contact in the heterojunction. Besides, the main free radicals were determined as e- and •O2-, and production level of free radicals were confirmed by radical trapping experiments. The possible degradation mechanism was proposed and discussed. Finally, this work provides a unique approach to in-situ preparation of heterojunction photocatalysts and demonstrates the prepared Bi4O5Br2 nanoplatelets/g-C3N5 photocatalysts have great potential in the waste water management.

Unraveling the metabolic shift in anaerobic digestion pathways associated with the alteration of onion skin waste concentration.

Onion skin waste (OSW) is common waste in developing countries, which can cause severe environmental pollution when not properly treated. Value-added products can be chemically extracted from OSW; however, that process is not economically feasible. Alternatively, dry anaerobic digestion (DAD) of OSW is a promising approach for both energy recovery and environment protection. The main hurdles during DAD of OSW can be the hydrolysis and acidification. In batch tests, sludge digestate (SD) rich with methanogens was co-digested with different fractions of OSW for enhancing hydrolysis and raising biogas productivity. The cumulative biogas production (CBP) was 36.6 ± 0.3 mL for sole DAD of SD (100% SD) and increased up to 281.9 ± 14.1 mL for (50% SD: 50% OSW) batch. Self-delignification of OSW took place by SD addition, where the lignin removal reached 75.3 ± 10.5% for (85% SD: 15% OSW) batch. Increasing the fraction of OSW (45% SD: 55% OSW) reduced the delignification by a value of 68.8%, where initial lignin concentration was 9.48 ± 1.6% in dry weight. Lignin breaking down resulted a high fraction of phenolic compounds (345.6 ± 58.8 mg gallic acid equivalent/g dry weight) in the fermentation medium, causing CBP drop (219.0 ± 28.5 mL). The presence of elements (K, Ca, Mg, Fe, Zn, Mn, S and P) in OSW improved the enzymatic activity, facilitated phenolic compounds degradation, shifted the metabolism towards acetate fermentation pathway, and raised biogas productivity. Acidogenesis was less affected by phenolic compounds than methanogenesis, causing higher H2 contents and lower CH4 contents, at batches with high share of OSW.

Phytomanagement of textile wastewater for dual biogas and biochar production: A techno-economic and sustainable approach.

Phytoremediation has been widely employed for industrial effluent treatment due to its cost-effectiveness and eco-friendliness. However, this process generates large amounts of exhausted plant biomass, requiring appropriate management strategies to avoid further environmental pollution. To the best of the authors' knowledge, this study is the first to address the recyclability of water hyacinth after textile wastewater (TWW) phytoremediation for dual biogas and biochar production. A hydroponic culture system was occupied by 163 g (plant mass) per L (TWW) and operated under 16:8 h light:dark cycle (sunlight), 70-80% relative humidity, and 22-25 °C temperature. This water hyacinth-based system achieved chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and dye removal efficiencies of 58.60 ± 2.63%, 35.27 ± 1.65%, and 38.49 ± 2.24%, respectively, at a TWW fraction of 100 %v/v. The plant characterization study revealed that phytoabsorption and phytoextraction could be the main mechanisms involved in TWW pollution reduction. The lignin and hemicellulose of water hyacinth were slightly degraded during phytoremediation, making the cellulose fibers simply accessible to enzymes' attack in the subsequent anaerobic digestion process. This hypothesis was validated by increasing the crystallinity index from 50.13% to 60.21% during TWW phytoremediation. The spent plant was cleaned and then co-digested (37 °C) with cow dung at 1:1 (w/w, dry basis) for bioenergy production. The generated biogas was 162.78 ± 8.34 mL CH4/g COD (i.e., 225.63 ± 11.36 mL CH4/g volatile solids), representing about 490% higher than the utilization of raw water hyacinth in a mono-digestion process. The pyrolysis of digestate-containing plant residues yielded biochar with concentrated cationic macroelements (K+, Mg2+, and Ca2+). The economic feasibility of the phytoremediation/co-digestion/pyrolysis combined system showed an initial investment of 2090 USD and a payback period of 9.08 yr. Because the project succeeded in recovering the cost of its initial investment, it could fulfill the targets of several sustainable development goals related to economic profitability, social acceptance, and environmental protection.

Preliminary quantitative assessment of the multidimensional impact of the COVID-19 pandemic on Sustainable Development Goals.

The intersectoral impacts of the COVID-19 pandemic on humanity raises concerns about its implications for sustainable development. Here, we examine a global quantitative impact of COVID-19 pandemic on Sustainable Development Goals (SDGs) across all 17 goals using 65 proxy indicators across 72 countries collected from April 2020 to February 2021. Our data-driven analysis indicated that adverse impacts of the pandemic have been particularly concerned on gender equality (Goal 5), affordable and clean energy (Goal 7), decent work and economic growth (Goal 8), sustainable cities and communities (Goal 11), and responsible consumption and production (Goal 12) with global scores estimated to be -0.38, -0.21, -0.28, -0.22 and -0.16, respectively. Country income level was a variable that strongly differentiates the responses to the pandemic (e.g., lower incomes had 14 negative goals compared to 11 and 4 negative goals assigned to middle- and high-income countries, respectively). However, Goals 5 and 8 were highly impacted worldwide regardless of income status. Furthermore, countries that had already higher performance in SDGs were less impacted by the pandemic, highlighting the importance of progress on the SDGs in increasing societal resilience to pandemics. The findings provide insights into the reinforcement of recovery policies (e.g., protecting vulnerable groups and transitioning to a green economy) and a basis for a quantitative discussion on the sectors to be prioritized.

Unraveling the capability of graphene nanosheets and γ-Fe2O3 nanoparticles to stimulate anammox granular sludge.

In this study, we investigated the potentials of nanomaterials to enhance anaerobic ammonium oxidation (anammox) process, in terms of nitrogen removal, microbial enrichment, and activity of key enzymes. Graphene nanosheets (GNs) and γ-Fe2O3 nanoparticles (NPs) were selected due to their catalytic functions as conductive material and electron shuttles, respectively. The obtained results revealed that the optimum dosage of GNs (10 mg/L) boosted the nitrogen removal rate (NRR) by 46 ± 3.1% compared to the control, with maximum NH4+-N and NO2--N removal of 86.5 ± 2.7% and 97.1 ± 0.5%, respectively. Moreover, hydrazine dehydrogenase (HDH) enzyme activity was augmented by 1.1-fold when using 10 mg/L GNs. The presence of GNs promoted the anammox granulation via enhancement of hydrophobic interaction of extracellular polymeric substances (EPS). Regarding the use of γ-Fe2O3 NPs, 100 mg/L dose increased NRR by 55 ± 3.8%; however, no contribution to HDH enzyme activity and a decrease in EPS compositions were observed. Given that the abiotic use of γ-Fe2O3 NPs further resulted in high adsorption efficiency (~92%), we conclude that the observed promotion due to γ-Fe2O3 NPs was mainly abiotic. Moreover, the 16S rRNA analysis revealed that the relative abundance of genus C. Jettenia (anammox related bacteria) increased from 11.9% to 12.3% when using 10 mg/L GNs, while declined to 8.3% at 100 mg/L γ-Fe2O3 NPs. Eventually, nanomaterials could stimulate the efficiency of anammox process, and this promotion and associated mechanism depend on their dose and composition.

Development and Application of a High-Precision Algorithm for Nontarget Identification of Organohalogens Based on Ultrahigh-Resolution Mass Spectrometry.

Brominated and/or chlorinated organic compounds (referred to as organohalogens) are frequently detected in natural and engineered environments. However, ultrahigh-resolution mass spectrometry (UHR-MS)-based nontargeted identification of organohalogens remains challenging because of the coexistence of a vast number of halogenated and nonhalogenated organic molecules. In this study, a new algorithm, namely, the NOMDBP code, was developed to simultaneously identify organohalogens and non-organohalogens from the UHR-MS spectra of natural and engineered waters. In addition to isotopic patterns, for the first time, three optional filter rules [i.e., selection for minimum nonoxygen heteroatoms, inspection of the presence of newly formed halogenated disinfection byproducts (Xn-DBPs), and of their precursors] were incorporated into our code, which can accurately identify DBP-associated peaks and further elucidate Xn-DBP generation and transformation mechanisms. The formula assignment ratio against 2815 previously reported organohalogens, and their 11,583 isotopologues exceeded 97%. Application of our algorithm to disinfected natural organic matter indicated that oxygen-containing Xn-DBP species accounted for a majority of the Xn-DBPs. Furthermore, brominated Xn-DBPs (Br-DBPs) were characterized by a higher degree of unsaturation compared to chlorinated Xn-DBPs. In addition to electrophilic substitution and electrophilic addition reactions, the decomposition/transformation pathway was found to be another important mechanism in Br-DBP formation. The results of this study highlight the superior potential of our code for the efficient detection of yet unknown organohalogens (including organohalogens bearing nonoxygen heteroatoms) in a nontargeted manner and for the identification of their generation mechanism occurring during the disinfection process.

Physiological responses of the freshwater N2 -fixing cyanobacterium Raphidiopsis raciborskii to Fe and N availabilities.

The cyanobacterium Raphidiopsis raciborskii is of environmental and social concern in view of its toxicity, bloom-forming characteristics and increasingly widespread occurrence. However, while availability of macronutrients and micronutrients such as N and Fe are critically important for the growth and metabolism of this organism, the physiological response of toxic and non-toxic strains of R. raciborskii to varying Fe and N availabilities remains unclear. By determining physiological parameters as a function of Fe and N availability, we demonstrate that R. raciborskii growth and N2 -fixing activity are facilitated at higher Fe availability under N2 -limited conditions with faster growth of the CS-506 (cylindrospermopsin-producing) strain compared with that of CS-509 (the non-toxic) strain. Radiolabelled Fe uptake assays indicated that R. raciborskii acclimated under Fe-limited conditions acquires Fe at significantly higher rates than under Fe replete conditions, principally via unchelated Fe(II) generated as a result of photoreduction of complexed Fe(III). While N2 -fixation of both strains occurred during both day and night, the CS-506 strain overall exhibited higher N2 -fixing and Fe uptake rates than the CS-509 strain under N-deficient and Fe-limited conditions. The findings of this study highlight that Fe availability is of significance for the ecological advantage of CS-506 over CS-509 in N-deficient freshwaters.

Physico-chemical and microbial characterization of compartment-wise profiles in an anammox baffled reactor.

In this study, compartment-wise investigation of an anammox baffled reactor (AnBR) was performed. The AnBR achieved steady-state conditions after a start-up period of ∼50 days and achieved NH4 and NO2 conversion percentages of 88.5 and 99.3%, respectively. Examination of the nitrogen mass balance revealed that an AnBR with a two-compartment configuration was sufficient for nitrogen loading rates (NLRs) ranging from 0.125 to 1.975 kg N/m3/d and resulted in a nitrogen removal efficiency (NRE) of 86.7-93.7%. Higher NLRs (4.04-5.05 kg N/m3/d) required four compartments to achieve an NRE of 82.2-87.1%. Further, an overall NLR increase of up to 5.93 ±â€¯0.23 kg N/m3/d resulted in complete AnBR failure. The maximum nitrogen removal rate was consistently recorded in the 1st compartment for all NLRs examined; as a result, this compartment exhibited the highest bacterial activity. Biomass concentration, specific anammox activity, extracellular polymeric substances, and average granule diameter in the 1st compartment with an overall NLR of 0.05 kg N/m3/d were estimated to be 11.2 gVSS/L, 0.03 mg N/gVSS/h, 84.3 mg/gVSS, and 0.65 mm, respectively. These values increased to 26.1 gVSS/L, 11.80 mg N/gVSS/h, 242.1 mg/gVSS, and 2.31 mm, respectively, when the overall NLR was incremented to 4.04 kg N/m3/d. However, a gradual reduction in bacterial activity was observed from the 1st to the 5th compartment. The microbial community analysis indicated that the dominant phyla in the 1st compartment (NLR of 0.252 kg N/m3/d) with the highest nitrogen removal were Chloroflexi (38.13%), Planctomycetes (22.62%), and Proteobacteria (14.75%).

Regulating acidogenesis and methanogenesis for the separated bio-generation of hydrogen and methane from saline-to-hypersaline industrial wastewater.

Given the limitations of acidogens and methanogens activities under saline environments, this work aims to optimize the main operational parameters affecting hydrogen and methane production from saline-to-hypersaline wastewater containing mono-ethylene glycol (MEG). MEG is the main contaminant in several saline industrial effluents. Anaerobic baffled reactor (ABR), as a multi-stage system, was used at different temperatures (i.e., 19-31 °C [ambient] and 35 °C), organic loading rates (OLRs) of 0.6-2.2 gCOD/L/d, and salinity of 5-35 gNaCl/L. Mesophilic conditions of 35 °C substantially promoted MEG biodegradability (92-98%) and hydrogen/methane productivity, even at elevated salinity. Hydrogen yield (HY) and methane yield (MY) peaked to 258 and 140 mL/gCODadd, respectively, at OLR 0.64 gCOD/L/d and salinity up to 20-25 gNaCl/L. An immobilized sludge ABR (ISABR), packed with polyurethane media, was further compared with classical ABR, resulting in 1.8-fold higher MY, at 35 gNaCl/L. Microbial analysis showed that introducing attached growth system (ISABR) substantially promoted methanogens abundance, which was dominated by genus Methanosarcina. Among bacterial genera, Acetobacterium was dominant, particularly in 1st compartment, representing MEG-degrading/salt-tolerant genus. At high salinity up to 35 gNaCl/L, the multi-phase and attached growth configuration can efficiently reduce the induced salt stress, particularly on methanogens, towards balanced and separated acidogenesis/methanogenesis. Overall, producing hydrogen and methane from anaerobic treatment of MEG-based saline wastewater is feasible at optimized parameters and configuration.

Effects of the chemical characteristics and concentration of inorganic suspended solids on nitrification in freshwater.

The effect of inorganic suspended solids (ISS) on nitrification in freshwater samples has been described inconsistently and remains unclear. This study therefore investigated the effects of the chemical characteristics and concentration of ISS on the nitrification rate by focusing on Nitrosomonas europaea and Nitrobacter winogradskyi as the two most dominant nitrification species in freshwater. Batch-wise experiments were conducted using three chemically well-characterized ISS (i.e. the clay minerals montmorillonite, sericite, and kaolinite in the concentration range 0-1,000 mg L-1). The results show that the ammonium oxidation rate constant (kNH4) was significantly affected by the ISS type, whereas changes in the ISS concentration had an insignificant effect on kNH4, except for kaolinite. The highest kNH4 was observed in samples containing sericite (kNH4, 0.067 L mg-1 day-1), followed by samples containing montmorillonite (kNH4, 0.044 L mg-1 day-1). The ammonium oxidation rate was low in the control and kaolinite samples. Nitrite oxidation was enhanced in the presence of all types of ISS. The rate constants of ISS-mediated nitrite oxidation (kNO2, 0.13-0.21 L mg-1 day-1) were not significantly different among the three types of ISS, but kNO2 was significantly affected by ISS concentration. Overall, our study indicated various effects of the ISS type and concentration on nitrification and, in particular, a notable positive effect of sericite.

Specific global responses to N and Fe nutrition in toxic and non-toxic Microcystis aeruginosa.

The bloom-forming cyanobacteria species Microcystis aeruginosa includes toxic and non-toxic (microcystin-producing) strains. Certain stress conditions stimulate synthesis of microcystin (MCYST) and enhance the binding of the MCYST molecule to proteins. In this quantitative proteomic study, we compared the response of a wild-type toxic strain PCC 7806, an mcyH(-) knockout non-toxic strain, and a naturally occurring non-toxic strain, PCC 7005, after 8 days in low iron (Fe) and nitrogen (N) starvation in order to assess the benefit of MCYST synthesis in non-optimal conditions. Fe limitation increased MCYST synthesis and caused an accumulation of phycobilisome proteins and the ferric iron transporter FutA only in the toxic PCC 7806 but not the non-toxic strains. In N starvation, photosynthetic, C and N metabolism proteins were more abundant in the non-toxic strains, as were chaperones and proteases. Significant interaction between nutrient availability and toxicity existed for thioredoxin peroxidase and several thioredoxin-regulated proteins. We propose a competition of MCYST for binding sites in thioredoxin-regulated proteins during oxidative stress (low Fe) but not in growth-limiting conditions (low N). This then leads to differences in the regulation of C:N metabolism in toxic and non-toxic M. aeruginosa in nutrient-replete and nutrient-limited conditions.

Competitive Effects of Calcium and Magnesium Ions on the Photochemical Transformation and Associated Cellular Uptake of Iron by the Freshwater Cyanobacterial Phytoplankton Microcystis aeruginosa.

Photochemical reduction of iron and iron uptake by Microcystis were investigated in a freshwater medium (pH 8) containing a range of calcium (Ca) and magnesium (Mg) ion concentrations (0.002-20 mM). In a medium containing the chelator ethylenediaminetetraacetic acid (EDTA), 50-fold increases in net photochemical formation rates of unchelated ferrous iron (Fe(II)') were observed as the concentration of calcium or magnesium metal (Me) was increased to exceed the concentration of EDTA. Kinetic modeling of iron transformation processes indicated that the facilitated Fe(II)' formation is attributed to Me-promoted photoreductive dissociation of the ferric iron-EDTA complex. In the medium containing Suwanee River fulvic acid, in contrast, the competitive effect of Me on photochemical Fe(II)' formation appears to be negligible due to the weak binding affinities of fulvic acid to Me. The cellular iron uptake rate in the EDTA-buffered system increased by ∼3-fold in the excess Me condition where the increased rate of photochemical Fe(II)' formation was observed, whereas the presence of Me resulted in a decrease in iron uptake rate in the fulvic acid system (by up to 5-fold). The decrease in iron uptake is likely caused by Me binding to iron transporters and other entities involved in intracellular iron transport. The findings of this study indicate a significant effect of Ca and Mg concentrations in natural waters on iron uptake by Microcystis, with the magnitude of effect depending strongly on ligand type.