Locally enhanced mixed-order model for chloramine decay in drinking water disinfection.

Chloramine is the second most popular disinfectant and is widely used in the disinfection of drinking water. For chloramine disinfection, some standards require the total chlorine concentration to be maintained in an appropriate range in the water distribution system. Therefore, exploring the mechanism of chloramine decay and deriving an accurate chloramine decay model helps to optimize the disinfection process and ensure water quality safety. This paper proposed a locally enhanced mixed-order(LEM) model consisting of the first order model and the mixed order model to describe chloramine auto-decomposition and decays caused by other reactions respectively. Via proving the parameter a and k2 related to temperatures instead of initial chloramine concentration, the model had been further simplified. Nine chloramine decay experiments with different initial chloramine concentrations and temperatures were designed and carried out to evaluate the new model performance for chloramine decay simulation. The research results showed that the simplified LEM model could simulate the whole process of chloramine decay well. Its accuracy evaluation indexes (R2 and SSE) were better than that obtained from the first order model and the mixed order model. This paper proposed a simple and accurate method to simulate the process of chloramine decay and had a guiding significance for water quality safety assurance.

Efficient nitrogen removal by multi-stage A/O mud membrane composite process with segmented influent: Performance and microbial community structure.

In this paper, a multi-stage A/O mud membrane composite process with segmented influent was constructed for the first time and compared with the traditional activated sludge process and the multi-stage A/O pure membrane process with segmented influent. The nitrogen removal efficiency of the process under different influencing factors was studied. Under the optimum conditions, the highest removal rate of ammonia nitrogen can reach 99%, and the average removal rate of total nitrogen was 80%. The removal rate of COD in effluent reached 93%. The relative abundance of Proteobacteria was the highest in the multi-stage A/O mud membrane composite reactor with segmented influent. The community diversity and richness of activated sludge and biofilm in aerobic pool were the highest. Dechloromonas, Flavobacterium and Rhodobacter were dominant bacteria, and they were aerobic denitrifying bacteria that significantly contributed to the removal rate of ammonia nitrogen.

Catalytic Asymmetric Oxidation of Amines to Hydroxylamines.

Chiral hydroxylamines are increasingly common structural elements in pharmaceuticals and agrochemicals, but their asymmetric synthesis remains challenging. Although enantioselective oxidation is the most straightforward method to prepare chiral oxides with a higher oxidation state, asymmetric and even nonasymmetric amine oxidation to hydroxylamines has been poorly addressed. We report a titanium-catalyzed asymmetric oxidation of racemic amines providing a broad range of structurally diverse chiral hydroxylamines with excellent chemo- and enantioselectivity. Notably, hydroxylamines bearing diverse substituent patterns on the stereocenters, including α,α-ester-alkyl, α,α-amide-alkyl, α,α-aryl-alkyl, α,α-alkynyl-alkyl, and α,α-dialkyl, are well tolerated with good functional group compatibility. Catalyst turnover numbers up to 5000 and selectivity factors up to 278 are observed. This finding offers a democratized platform to chiral hydroxylamines as design elements for drug discovery and provides insights into metal-catalyzed asymmetric oxidation of challenging substrates.

Biofilm on the pipeline wall is an important transmission route of resistome in drinking water distribution system.

Due to the intensive use of antibiotics, the drinking water distribution system (DWDS) has become one of the hotspots of antibiotic resistance. However, little is known about the role of biofilm in the aspect of spreading resistance in DWDS. In present study, four lab-scale biological annular reactors (BAR) were constructed to investigate the transmission of ARGs exposed to a certain amount of antibiotic (sulfamethoxazole) synergistic disinfectants. It was emphasized that pipe wall biofilm was an important way for ARGs to propagate in the pipeline, and the results were quantified by constructing an operational taxonomic unit (OTU) network map. The network analysis results showed the biofilm contribution to waterborne bacteria was finally estimated to be 51.45% and 34.27% in polyethylen (PE) pipe and ductile iron (DI) pipe, respectively. The proportion of vertical gene transfer (VGT) in biofilm was higher than that in water, and the occurrence of this situation had little relationship with the selection of pipe type. Overall, this study revealed how biofilm promoted the transmission of resistome in bulk water, which can provide insights into assessing biofilm-associated risks and optimizing pipe material selection for biofilm control in DWDS.

The mixed-order chlorine decay model with an analytical solution and corresponding trihalomethane generation model in drinking water.

Ensuring effective drinking water disinfection, remaining a certain amount of residual chlorine, and controlling disinfection by-product formation were very important for guarantying water quality safety and protecting public health; thus, the chlorine decay model and corresponding disinfection by-product formation model were necessary. This paper proposed a mixed-order chlorine bulk decay model (two parameters) based on Taylor's formula and derived its analytical solution. The accuracy of the mixed-order model was evaluated by comparing it with the nth-order model. To optimize the model and reduce the number of parameters required to be calibrated, the relationship of parameters with temperature, initial chlorine concentration, TOC and inorganic substance (ammonia nitrogen and iodide ion) was explored. The result proved that one of the parameters could be regarded as temperature dependent only. Meanwhile, the temperature equation of the model parameters was established by the Arrhenius formula. Subsequently, this paper selected trihalomethane as the target and study the linear relationship between chlorine consumption and trihalomethane formation. The results indicated that the liner slope had little correlation with initial chlorine concentration and temperature. On this basis, the corresponding trihalomethane model was built and its performance was proven to be good. The modeling developed in this work could be applied to drinking water distribution systems for residual chlorine and trihalomethane prediction, and provided a reference for the decision involving water quality.

Accelerated electron transfer process via MOF-derived FeCo/C for enhanced degradation of antibiotic contaminants towards heterogeneous electro-Fenton system.

The Fe(III) to Fe(II) process limits the rate of the electro-Fenton system. In this study, MIL-101(Fe) derived porous carbon skeleton-coated FeCo bimetallic catalyst Fe4/Co@PC-700 was prepared as a heterogeneous electro-Fenton (EF) catalytic process. The experimental results showed its good performance in catalytic removal of antibiotic contaminants, the rate constant of tetracycline (TC) degradation catalyzed by Fe4/Co@PC-700 was 8.93 times higher than that of Fe@PC-700 under the pH conditions of raw water (pH = 5.86), exhibited good removal of TC, oxytetracycline (OTC), hygromycin (CTC), chloramphenicol (CAP) and ciprofloxacin (CIP). It was shown that the introduction of Co promoted more Fe0 production, allowing the material to exhibit faster Fe(III)/Fe(II) cycling rates. 1O2 and high-priced metal oxygen species were identified as the main active species of the system, in addition to the analysis of possible degradation pathways and toxicity of intermediates of TC. Finally, the stability and adaptability of Fe4/Co@PC-700 and EF systems to different water matrices were evaluated, showing that Fe4/Co@PC-700 was easy to recover and could be applied to different water matrices. This study provides a reference for the design and system application of heterogeneous EF catalysts.

Catalytic activity of H2O2 by goethite and lepidocrocite: Insight from 5-bromosalicylic acid removal mechanism and density functional theory calculation (ID:CHEM114760).

We have compared the elimination of 5-bromosalicylic acid (BSA) in the systems of goethite (α-FeOOH)/H2O2 and lepidocrocite (γ-FeOOH)/H2O2. The results demonstrated that BSA (10 mg L-1) could be successfully adsorbed on α- and γ-FeOOH (0.5 g L-1) and then effectively degraded after the addition of H2O2 (14.7 mM). BSA adsorption on both α- and γ-FeOOH followed pseudo-second order adsorption kinetic models, with γ-FeOOH having greater adsorption ability than α-FeOOH. In the α-FeOOH/H2O2 system, BSA degradation was well fitted with the pseudo-second order kinetics, whereas the oxidation in γ-FeOOH/H2O2 system had a two-stage pseudo-first order kinetics. Electron paramagnetic resonance (EPR) results for these two systems revealed the presence of •OH and •OOH, and further tests with radical captures demonstrated their dominance in degrading BSA. Based on the electronic structure analysis, electrons were more easily transferred from the H2O2 molecule to the Fe atoms of α-FeOOH, explaining the density functional theory (DFT) calculation results, which showed that α-FeOOH performed better in catalyzing the decomposition of H2O2. However, the free radicals are more likely to desorb from γ-FeOOH, which made the γ-FeOOH/H2O2 system more efficient in degrading BSA.

Deciphering the distribution and microbial secretors of extracellular polymeric substances associated antibiotic resistance genes in tube wall biofilm.

Antibiotics and disinfectants have both been proposed to exert selective pressures on the biofilm as well as affecting the emergence and spread of antibiotic resistance genes (ARGs). However, the transfer mechanism of ARGs in drinking water distribution system (DWDS) under the coupling effect of antibiotics and disinfectants has not been completely understood. In the current study, four lab-scale biological annular reactors (BARs) were constructed to evaluate the effects of sulfamethoxazole (SMX) and NaClO coupling in DWDS and reveal the related mechanisms of ARGs proliferation. TetM was abundant in both the liquid phase and the biofilm, and redundancy analysis showed that the total organic carbon (TOC) and temperature were significantly correlated with ARGs in the water phase. There was a significant correlation between the relative abundance of ARGs in the biofilm phase and extracellular polymeric substances (EPS). Additionally, the proliferation and spread of ARGs in water phase were related to microbial community structure. Partial least-squares path modeling showed that antibiotic concentration may influence ARGs by affecting MGEs. These findings help us to better understand the diffusion process of ARGs in drinking water and provide a theoretical support for technologies to control ARGs at the front of pipeline.

Cu-based perovskite as a novel CWPO catalyst for petroleum refining wastewater treatment: Performance, toxicity and mechanism.

For the first time, Cu-based perovskite oxides were used as catalysts to treat highly toxic and refractory petroleum refining wastewater based on catalytic wet peroxide oxidation (CWPO) technology. Perovskite La2CuO4 was synthesized by sol-gel method. A series of characterizations showed that the synthesized catalyst particles are tetragonal phase perovskite structure. The experimental results showed that under the conditions of catalyst dosage of 0.75 g, temperature of 100 â„ƒ and reaction time of 30 min, the COD removal rate was 89.58 %, the TOC removal rate was 87.38 %. The morphology and structure of the catalyst before and after the reaction proved that the catalyst has strong stability and catalytic activity. The components of raw water, Wet Air Oxidation (WAO) effluent and CWPO effluent were compared and analyzed by Gas Chromatography-Mass Spectrometry (GC-MS), and the possible mechanism and path of WAO and CWPO degradation of petroleum refining wastewater were further explored. The changes of Cu components in La2CuO4 before and after CWPO reaction and the transformation of lattice oxygen and adsorbed oxygen were analyzed by X-ray Photoelectron Spectroscopy (XPS). The involvement of Cu (Ⅱ) /Cu (Ⅰ) in the activation of H2O2 was speculated. Finally, the biotoxicity of raw water, WAO effluent and CWPO effluent was predicted. The results provide reference value for the application of catalyst La2CuO4 in various petrochemical wastewater.

Somalactams A-D: Anti-inflammatory Macrolide Lactams with Unique Ring Systems from an Arctic Actinomycete Strain.

Four new PKS-NRPS-derived macrolide lactams with three unique ring fusion types were discovered from the Arctic sponge associated actinomycete Streptomyces somaliensis 1107 using a genome mining strategy. Their structures were elucidated by a combination of MS, NMR spectroscopic analysis, and single-crystal X-ray diffraction. Biosynthetically, a novel gene cluster sml consisting of three polyketide synthases and one hybrid polyketide synthase-nonribosomal peptide synthetase together with cytochrome P450s and flavin-containing monooxygenases and oxidoreductases was demonstrated to assemble the unique skeleton. Pharmacological studies revealed that compound 1 displayed a potent anti-inflammatory effect without cytotoxicity. It inhibited IL-6 and TNF-α release in the serum of LPS-stimulated RAW264.7 macrophage cells with IC50 values of 5.76 and 0.18 µM, respectively, and modulated the MAPK pathway. Moreover, compound 1 alleviated LPS-induced systemic inflammation in our transgenic fluorescent zebrafish model.

Activation of the combined hydrogen peroxide and peroxymonosulphate by lepidocrocite for chloramphenicol removal: kinetics and mechanisms.

The main compositions of pipe deposits from water distribution networks are potential iron resources, which can be used as catalysts to activate the combined hydrogen peroxide (HP) and peroxymonosulphate (PMS) system to produce reactive oxidative species (ROSs) to degrade pollutants. As a result, the degradation efficiency of chloramphenicol (CAP) in the HP/PMS dual-oxidant system could reach as high as 75.21% within 100 min with hydroxylamine (HA) assistance, and the dual-oxidant method had a wide pH applied range. To explore the mechanism of the dual-oxidant system in detail, several main affecting factors were investigated. In addition, the hydroxyl radical(•OH) was identified as the predominant radicals by Electron paramagnetic resonance (EPR) and the Radical scavenger test (RST). According to the competition kinetics experiment, the reaction rate of CAP with •OH was 1.933(± 0.052) × 1010 M-1s-1 in the HP/PMS dual-oxidant system, which was higher than the HP single oxidant system (6.10(± 0.036) × 109 M-1s-1). And the role of HA was explored , including reduction and competition. Six degradation products were detected by the liquid chromatography-mass spectrometry (LC-MS) and their toxicity was analyzed by the ecological structure-activity relationship (ECOSAR) predictive model. These findings further provide a theoretical basis for the practical application of pipe deposits and advance the development of in-situ removal of pollutants in water distribution networks in the future promisingly.

Copper-based Ruddlesden-Popper perovskite oxides activated hydrogen peroxide for coal pyrolysis wastewater (CPW) degradation: Performance and mechanism.

Coal pyrolysis wastewater (CPW) contained all kinds of toxic and harmful components, which would seriously threaten the natural environment and human health. However, the traditional advanced oxidation processes frequently failed to remove phenolic substances. An A2BO4-type perovskite (La2CuO4) was successfully synthesized through sol-gel process and first applied in the treatment of CPW. More than 90% of 3, 5-dimethylphenol (DMP) was removed within 200 min at neutral conditions. Moreover, La2CuO4 also displayed excellent catalytic activity and stability in the actual CPW treatment process. Results demonstrated that DMP was removed through the attack of ∙OH, ∙O2- and 1O2 in La2CuO4/H2O2 system. The La2CuO4 were more favorable for H2O2 activation and have a lower adsorption energy than LaFeO3. XPS of fresh and spent La2CuO4 illustrated that the decomposition of hydrogen peroxide (H2O2) was mainly due to the redox cycle between surface copper and oxygen species. Moreover, the possible degradation pathway of DMP was deduced by identifying degradation products and analyzing density functional theory (DFT) calculations. This research provided a novel strategy for the development of perovskite-based catalytic materials on the treatment of practical CPW.

Cobalt mediated perovskite as efficient Fenton-like catalysts for the tetracycline removal over a neutral condition: The importance of superoxide radical.

Cobalt mediated perovskite oxides (Ca-Fe-Co-x) were prepared for heterogeneous Fenton-like, which exhibited excellent tetracycline (TC) degradation efficiency and wider pH suitability (3-11). Experimental results showed that Ca-Fe-Co-1.0 sample displayed the highest degradation rate could reach 80.5% under neutral conditions, and maintain at around 80% after four cycles. The analysis of degradation mechanism showed that the redox of Fe2+/Fe3+ and Co2+/Co3+ significant enhanced the activation of H2O2 to superoxide radical (∙O2-). Meanwhile, the hydroxyl radical (∙OH) was also detected by ESR analysis. In addition, the possible degradation pathway and mechanism of TC were deduced via UPLC-QTOF/MS analysis and density functional theory (DFT) calculations. The toxicity of TC and its intermediates were also evaluated by the ECOSAR software. The Ca-Fe-Co-1.0/nanocellulose aerogel (NCA) displayed highly removal efficiency of TC wastewater in the long-term operation conduction. This study provided a feasible method to design and synthesis heterogeneous Fenton-like catalysts for antibiotic degradation.

Effects of a novel Mg-C micro-electrolysis system for phenolic wastewater degradation: material characterization, influencing factors, and model optimization.

This study investigated a novel magnesium carbon micro-electrolysis (Mg-C ME) system for strengthening the removal of phenolic compounds in wastewater. The effects of the Mg/C mass ratio, aeration intensity, initial pH and reaction time on the degradation of three phenolic compounds and the COD removal efficiency in the simulated wastewater were evaluated using one-factor-at-a-time (OFAT) method. The optimum values obtained for the Mg/C mass ratio, aeration intensity, initial pH and reaction time were 3:1, 4.0 L/(L·min), 5.0 and 2.5 h, respectively. The experimental removal rates of catechol, resorcinol, and phenol, under the mentioned conditions, were obtained to be 95.6%, 71.5%, and 48.8%, respectively. Meanwhile, the COD removal rates were 63.8%,44.7%,34.0%, respectively. Moreover, experiments were designed and analyzed based on the box-based designing response surface (BBD-RSM) method. According to the results, the Mg/C mass ratio was the most significant variable showing incremental effect on the removal efficiency of catechol in a way that maximum removal efficiency of catechol was achieved in Mg/C mass ratio of 3.23:1. The validation experiments showed that the maximum removal efficiency of catechol was 96.24% under optimization conditions. Resorcinol degradation characteristics analysis indicated that the Mg-C ME system performed a key function in phenolic compounds elimination. Results showed that the Mg-C ME has a considerable capability in removing the phenolic compounds and COD. Thus, it could be considered as an efficient pretreatment choice for treating phenolic wastewater in the future.

Clinical evaluation of acute necrotizing encephalopathy in children.

Objective: Acute necrotizing encephalopathy (ANE) is a rare but severe encephalopathy and is associated with a high morbidity and mortality. We aimed to analyze and compare the clinical features and predictive indicators of pediatric ANE. Materials and methods: This retrospective study included children with ANE diagnosed at Guangzhou Women and Children's Medical Center between November 2018 and January 2020. Pediatric patients' information, including clinical characteristics, laboratory tests, neuroelectrophysiology and brain magnetic resonance imaging (MRI) findings, MRI score, brainstem auditory evoked potential (BAEP) grades, ANE severity scores (ANE-SS), and modified Rankin scale (mRS), were collected. Results: Twelve ANE patients were included. Among them, one patient (8.3%) died from brainstem dysfunction, one (8.3%) recovered and 10 (83.3%) experienced neurological sequelae. All patients had an initial viral infection and neurological symptoms such as acute disturbance of consciousness (ADOC) or seizure, and the interval from onset of the disease to neurological manifestations was 3 (1.25-3) days. MRI score-I ranged from 1 to 3 (1.8 ± 0.7), MRI score-II ranged from 1 to 4 (2.5 ± 1.1). ANE-SS varied from 1 to 6 (3.9 ± 1.3). The scores of mRS were from 0 to 6 (2.9 ± 1.7). Higher MRI score were associated with worse outcomes, while the BAEP grade and ANE-SS score were not significantly associated with mRS. Conclusion: ANE is a severe encephalopathy syndrome with rapid progression, resulting in serious neurological sequelae. Compared with BAEP grade and ANE-SS, brain MRI shows more comprehensive advantages in predicting the prognosis of ANE patients. More in-depth research and better indicators are still needed to support the evaluation and treatment of ANE.

Fe3O4-CuO@Lignite activated coke activated persulfate advanced treatment of phenolic wastewater from coal chemical industry.

In this study, lignite activated coke (LAC) was used as the carrier for the first time, Fe3O4-CuO composite metal oxide was used as the main active material, and the nano-scale magnetic supported composite metal oxide Fe3O4-CuO@LAC catalyst was synthesized for the first time, which can effectively activate the active oxygen in peroxodisulfate (PS). XRD, FTIR, BET, SEM, XPS and other analysis results showed that there was particulate matter with spherical structure on the surface of the active coke, and its diffraction peaks matched well with the characteristic peaks of Fe3O4 and CuO, and it was a mesoporous structure with a specific surface area of 619.090 m2 g-1. By optimizing the experimental conditions, the results showed that more than 92% of hydroquinone can be removed under the conditions of hydroquinone concentration of 50 mg/L, pH = 5, adding 0.1 g/L catalyst and 3 mmol/L PS. EPR and quenching experiments proved that there were four reactive oxygen species in the reaction system ·OH, SO4-·, O2-· and 1O2. According to the degradation products of hydroquinone detected by LC-MS, the possible degradation path was deduced which laid a foundation for solving the problem of difficult treatment of phenol-containing wastewater in coal chemical industry.

Goethite and lepidocrocite catalyzing different double-oxidant systems to degrade chlorophenol.

Goethite and lepidocrocite, as the main compositions of pipe deposits in the water distribution network, could be used as a catalyst for advanced oxidation processes (AOPs). This research utilizes them to activate PDS/H2O2 and PMS/H2O2 degrading the 2,4,6-trichlorophenol, respectively. To describe the incomplete degradation of pollutants and reflect the induction period, a modified first-order model has been proposed and used to analyze degradation differences under several key affecting factors. The results revealed that the PDS/H2O2 system has a synergy effect in the 2,4,6-trichlorophenol degradation process. The possible degradation pathways and intermediate products were confirmed by gas chromatograph-mass spectrometry (GC-MS). The paper provides a new idea for the effective use of pipe deposits to remove chlorophenols from drinking water, which is of great significance to ensure water quality safety.

Heterogeneous activation of H2O2/Na2S2O8 with iron ore from water distribution networks for pollutant removal.

In this study, we investigated using the main composition of pipe deposits from water distribution networks as catalyst to activate dual-oxidant H2O2/Na2S2O8 system to produce radicals for perchloroethylene and chloramphenicol removal. According to the results, the degradation efficiency of perchloroethylene by H2O2/Na2S2O8 system was 92.05% within 8 h. Due to the slow conversion between ≡Fe3+ and ≡Fe2+, the hydroxylamine was introduced to reduce reaction time. As for the results, the degradation efficiency of chloramphenicol in the H2O2/Na2S2O8 system with hydroxylamine assistance was 73.31% within 100 min. Meanwhile, several key affecting factors and the kinetic models were investigated. The primary radicals were identified by electron paramagnetic resonance and radical scavenging tests. Eleven degradation products were confirmed by high-resolution liquid chromatography-mass spectrometry. The result of this study provided the theoretical basis for resource utilization of pipe deposits in water treatment in case of emerging contamination events.

Antibiotic enhances the spread of antibiotic resistance among chlorine-resistant bacteria in drinking water distribution system.

The extensive use of antibiotics leads to the occurrences of antibiotic resistance genes (ARGs) in aquatic environment. As an emerging environmental pollutant, its pollution in aquatic environment has aroused widespread concern. However, the residues of antibiotics and antibiotic resistance genes in drinking water distribution system were barely reported up to now. Here, we studied the correlation and coordination between chlorine resistance mechanism and antibiotic resistance mechanism of chlorine-resistant bacteria. Antibiotics induce the resistance of chlorine-resistant bacteria (CRB) to NaClO, so that low-dose disinfectants can not inactivate CRB. We put forward a strategy to control the growth of CRB by controlling the concentration of biodegradable dissolved organic carbon (BDOC) in the front section of the water network. Moreover, We screened two strains of chlorine-resistant bacteria with different antibiotic resistance after mixed culture, the results showed that antibiotic resistance could spread horizontally among different kinds of bacteria. Then, the non-pathogenic bacteria can be used as a carrier, causing the pathogen to become resistant to antibiotic, and ultimately pose harm to human health. Generally, the antibiotic, antibiotic resistant genes, and the chlorine disinfectants added in water treatment plants will interact with bacteria in the water supply pipe network, which causes pollution to drinking water.

Moderate Specific Surface Areas Help Three-Dimensional Frameworks Achieve Dendrite-Free Potassium-Metal Anodes.

The inevitable problem of dendrites growth has hampered the further development of K metal anodes. Constructing a three-dimensional anode framework and potassiophilic nanocoating is an effective way to enlarge the specific surface area, reduce the local current density, and inhibit the formation of K dendrites. However, the effects of the electrochemically active surface area (ECSA) of the framework on deposition behavior have not been clarified. Hence, SnS2 nanosheets with different sizes are loaded on the surface of carbon paper (SnS2@CP) to improve the potassiophilicity and realize dendrite-free K-metal anodes. Experiments reveal that the size of SnS2 nanosheets would determine the ECSA of the framework, while the ECSA reveals the relative sizes of specific surface areas of frameworks. Excessive or limited specific surface areas will cause morphological collapse or weak potassiophilicity during potassiation, respectively, thus leading to high nucleation overpotential. The moderate specific surface area and abundant and stable potassiophilic sites prompt the SnS2@CP framework to achieve uniform electrodeposition of K. A low nucleation overpotential of 11.2 mV and a cycle life of more than 800 h are exhibited at a current density of 0.25 mA cm-2, indicating the directional strategy for stable and safe K metal anodes.