Frontiers of Environmental Science & Engineering

ISSN 2095-2201

ISSN 2095-221X(Online)

CN 10-1013/X

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Municipal wastewater treatment in China: Development history and future perspectives
Jiuhui Qu, Hongchen Wang, Kaijun Wang, Gang Yu, Bing Ke, Han-Qing Yu, Hongqiang Ren, Xingcan Zheng, Ji Li, Wen-Wei Li, Song Gao, Hui Gong
Front. Environ. Sci. Eng.    2019, 13 (6): 88-.
Abstract   HTML   PDF (1489KB)

The history of China’s municipal wastewater management is revisited.

The remaining challenges in wastewater sector in China are identified.

New concept municipal wastewater treatment plants are highlighted.

An integrated plant of energy, water and fertilizer recovery is envisaged.

China has the world’s largest and still growing wastewater sector and water market, thus its future development will have profound influence on the world. The high-speed development of China’s wastewater sector over the past 40 years has forged its global leading treatment capacity and innovation ability. However, many problems were left behind, including underdeveloped sewers and sludge disposal facilities, low sustainability of the treatment processes, questionable wastewater treatment plant (WWTP) effluent discharge standards, and lacking global thinking on harmonious development between wastewater management, human society and the nature. Addressing these challenges calls for fundamental changes in target design, policy and technologies. In this mini-review, we revisit the development history of China’s municipal wastewater management and identify the remaining challenges. Also, we highlight the future needs of sustainable development and exploring China’s own wastewater management path, and outlook the future from several aspects including targets of wastewater management, policies and technologies, especially the new concept WWTP. Furthermore, we envisage the establishment of new-generation WWTPs with the vision of turning WWTP from a site of pollutant removal into a plant of energy, water and fertilizer recovery and an integrated part urban ecology in China.

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Cited: WebOfScience(9)
Excitation-emission matrix (EEM) fluorescence spectroscopy for characterization of organic matter in membrane bioreactors: Principles, methods and applications
Jinlan Yu, Kang Xiao, Wenchao Xue, Yue-xiao Shen, Jihua Tan, Shuai Liang, Yanfen Wang, Xia Huang
Front. Environ. Sci. Eng.    2020, 14 (2): 31-.
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• Principles and methods for fluorescence EEM are systematically outlined.

• Fluorophore peak/region/component and energy information can be extracted from EEM.

• EEM can fingerprint the physical/chemical/biological properties of DOM in MBRs.

• EEM is useful for tracking pollutant transformation and membrane retention/fouling.

• Improvements are still needed to overcome limitations for further studies.

The membrane bioreactor (MBR) technology is a rising star for wastewater treatment. The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter (DOM) in the system. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, a powerful tool for the rapid and sensitive characterization of DOM, has been extensively applied in MBR studies; however, only a limited portion of the EEM fingerprinting information was utilized. This paper revisits the principles and methods of fluorescence EEM, and reviews the recent progress in applying EEM to characterize DOM in MBR studies. We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity, wavelength regional distribution, and spectral deconvolution (giving fluorescent component loadings/scores), and discussed how to use the information to interpret the chemical compositions, physiochemical properties, biological activities, membrane retention/fouling behaviors, and migration/transformation fates of DOM in MBR systems. In addition to conventional EEM indicators, novel fluorescent parameters are summarized for potential use, including quantum yield, Stokes shift, excited energy state, and fluorescence lifetime. The current limitations of EEM-based DOM characterization are also discussed, with possible measures proposed to improve applications in MBR monitoring.

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Cited: WebOfScience(1)
Enhanced carbon tetrachloride degradation by hydroxylamine in ferrous ion activated calcium peroxide in the presence of formic acid
Wenchao Jiang, Ping Tang, Zhen Liu, Huan He, Qian Sui, Shuguang Lyu
Front. Environ. Sci. Eng.    2020, 14 (2): 18-.
Abstract   HTML   PDF (769KB)

• Complete CT degradation was achieved by employing HA to CP/Fe(II)/FA process.

• Quantitative detection of Fe(II) regeneration and HO• production was investigated.

• Benzoic acid outcompeted FA for the reaction with HO•.

• CO2 was the dominant reductive radical for CT removal.

• Effects of solution matrix on CT removal were conducted.

Hydroxyl radicals (HO•) show low reactivity with perchlorinated hydrocarbons, such as carbon tetrachloride (CT), in conventional Fenton reactions, therefore, the generation of reductive radicals has attracted increasing attention. This study investigated the enhancement of CT degradation by the synergistic effects of hydroxylamine (HA) and formic acid (FA) (initial [CT] = 0.13 mmol/L) in a Fe(II) activated calcium peroxide (CP) Fenton process. CT degradation increased from 56.6% to 99.9% with the addition of 0.78 mmol/L HA to the CP/Fe(II)/FA/CT process in a molar ratio of 12/6/12/1. The results also showed that the presence of HA enhanced the regeneration of Fe(II) from Fe(III), and the production of HO• increased one-fold when employing benzoic acid as the HO• probe. Additionally, FA slightly improves the production of HO•. A study of the mechanism confirmed that the carbon dioxide radical (CO2), a strong reductant generated by the reaction between FA and HO•, was the dominant radical responsible for CT degradation. Almost complete CT dechlorination was achieved in the process. The presence of humic acid and chloride ion slightly decreased CT removal, while high doses of bicarbonate and high pH inhibited CT degradation. This study helps us to better understand the synergistic roles of FA and HA for HO• and CO2 generation and the removal of perchlorinated hydrocarbons in modified Fenton systems.

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Advances in Fe(III) bioreduction and its application prospect for groundwater remediation: A review
Yu Jiang, Beidou Xi, Rui Li, Mingxiao Li, Zheng Xu, Yuning Yang, Shaobo Gao
Front. Environ. Sci. Eng.    2019, 13 (6): 89-.
Abstract   HTML   PDF (1027KB)

Microbial Fe(III) reduction is closely related to the fate of pollutants.

Bioavailability of crystalline Fe(III) oxide is restricted due to thermodynamics.

Amorphous Fe(III) (hydro)oxides are more bioavailable.

Enrichment and incubation of Fe(III) reducing bacteria are significant.

Microbial Fe(III) reduction is a significant driving force for the biogeochemical cycles of C, O, P, S, N, and dominates the natural bio-purification of contaminants in groundwater (e.g., petroleum hydrocarbons, chlorinated ethane, and chromium). In this review, the mechanisms and environmental significance of Fe(III) (hydro)oxides bioreduction are summarized. Compared with crystalline Fe(III) (hydro)oxides, amorphous Fe(III) (hydro)oxides are more bioavailable. Ligand and electron shuttle both play an important role in microbial Fe(III) reduction. The restrictive factors of Fe(III) (hydro)oxides bioreduction should be further investigated to reveal the characteristics and mechanisms of the process. It will improve the bioavailability of crystalline Fe(III) (hydro)oxides and accelerate the anaerobic oxidation efficiency of the reduction state pollutants. Furthermore, the approach to extract, culture, and incubate the functional Fe(III) reducing bacteria from actual complicated environment, and applying it to the bioremediation of organic, ammonia, and heavy metals contaminated groundwater will become a research topic in the future. There are a broad application prospects of Fe(III) (hydro)oxides bioreduction to groundwater bioremediation, which includes the in situ injection and permeable reactive barriers and the innovative Kariz wells system. The study provides an important reference for the treatment of reduced pollutants in contaminated groundwater.

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Cited: WebOfScience(2)
Increasing prevalence of antibiotic resistance genes in manured agricultural soils in northern China
Nan Wu, Weiyu Zhang, Shiyu Xie, Ming Zeng, Haixue Liu, Jinghui Yang, Xinyuan Liu, Fan Yang
Front. Environ. Sci. Eng.    2020, 14 (1): 1-.
Abstract   HTML   PDF (1062KB)

• Manure application increased the abundances of ARGs and MGEs in agricultural soils.

• Five classes of ARGs and two MGEs were prevalent in manured and unfertilized soils.

• Genera Pseudomonas and Bacteroidetes might be the dominant hosts of intI1 and ermF.

• The abundances of ARGs positively correlated with TC, TN, OM, Cu, Zn, Pb and MGEs.

Land application of manure tends to result in the dissemination of antibiotic resistance in the environment. In this study, the influence of long-term manure application on the enrichment of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in agricultural soils was investigated. All the analyzed eight ARGs (tetA, tetW, tetX, sulI, sulII, ermF, aac(6’)-Ib-cr and blaTEM) and two MGEs (intI1 and Tn916/1545) were detected in both the manured and control soils, with relative abundances ranging from 10-6 to 10-2. Compared with the control soil, the relative abundances of ARGs and MGEs in manured soils were enriched 1.0–18.1 fold and 0.6–69.1 fold, respectively. High-throughput sequencing analysis suggested that at the phylum level, the bacteria carrying intI1 and ermF might be mainly affiliated with Proteobacteria and Bacteroides, respectively. The dominant genera carrying intI1 and ermF could be Pseudomonas and Bacteroides, independent of manure application. Correlation analysis revealed that ARGs had strong links with soil physicochemical properties (TC, TN, and OM), heavy metals (Cu, Zn and Pb) and MGEs, indicating that the profile and spread of ARGs might be driven by the combined impacts of multiple factors. In contrast, soil pH and C/N exhibited no significant relationships with ARGs. Our findings provide evidence that long-term manure application could enhance the prevalence and stimulate the propagation of antibiotic resistance in agricultural soils.

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Cited: WebOfScience(1)
Identifying factors that influence soil heavy metals by using categorical regression analysis: A case study in Beijing, China
Jun Yang, Jingyun Wang, Pengwei Qiao, Yuanming Zheng, Junxing Yang, Tongbin Chen, Mei Lei, Xiaoming Wan, Xiaoyong Zhou
Front. Environ. Sci. Eng.    2020, 14 (3): 37-.
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• A method was proposed to identify the main influence factors of soil heavy metals.

• The influence degree of different environmental factors was ranked.

• Parent material, soil type, land use and industrial activity were main factors.

• Interactions between some factors obviously affected soil heavy metal distribution.

Identifying the factors that influence the heavy metal contents of soil could reveal the sources of soil heavy metal pollution. In this study, a categorical regression was used to identify the factors that influence soil heavy metals. First, environmental factors were associated with soil heavy metal data, and then, the degree of influence of different factors on the soil heavy metal contents in Beijing was analyzed using a categorical regression. The results showed that the soil parent material, soil type, land use type, and industrial activity were the main influencing factors, which suggested that these four factors were important sources of soil heavy metals in Beijing. In addition, population density had a certain influence on the soil Pb and Zn contents. The distribution of soil As, Cd, Pb, and Zn was markedly influenced by interactions, such as traffic activity and land use type, industrial activity and population density. The spatial distribution of soil heavy metal hotspots corresponded well with the influencing factors, such as industrial activity, population density, and soil parent material. In this study, the main factors affecting soil heavy metals were identified, and the degree of their influence was ranked. A categorical regression represents a suitable method for identifying the factors that influence soil heavy metal contents and could be used to study the genetic process of regional soil heavy metal pollution.

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Characteristic and correlation analysis of influent and energy consumption of wastewater treatment plants in Taihu Basin
Luxi Zou, Huaibo Li, Shuo Wang, Kaikai Zheng, Yan Wang, Guocheng Du, Ji Li
Front. Environ. Sci. Eng.    2019, 13 (6): 83-.
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Poor biodegradability and insufficient carbon source are discovered from influent.

Influent indices presented positively normal distribution or skewed distribution.

Average energy consumption of WWTPs in Taihu Basin was as high as 0.458 kWh/m3.

Energy consumption increases with the increase in influent volume and COD reduction.

The total energy consumption decreases with the NH3-N reduction.

The water quality and energy consumption of wastewater treatment plants (WWTPs) in Taihu Basin were evaluated on the basis of the operation data from 204 municipal WWTPs in the basin by using various statistical methods. The influent ammonia nitrogen (NH3-N) and total nitrogen (TN) of WWTPs in Taihu Basin showed normal distribution, whereas chemical oxygen demand (COD), biochemical oxygen demand (BOD5), suspended solid (SS), and total phosphorus (TP) showed positively skewed distribution. The influent BOD5/COD was 0.4%–0.6%, only 39.2% SS/BOD5 exceeded the standard by 36.3%, the average BOD5/TN was 3.82, and the probability of influent BOD5/TP>20 was 82.8%. The average energy consumption of WWTPs in Taihu Basin in 2017 was 0.458 kWh/m3. The specific energy consumption of WWTPs with a daily treatment capacity of more than 5 × 104 m3 in Taihu Basin was stable at 0.33 kWh/m3. A power function relationship was observed between the reduction in COD and NH3-N and the specific energy consumption of pollutant reduction, and the higher the pollutant reduction is, the lower the specific energy consumption of pollutant reduction presents. In addition, a linear relationship existed between the energy consumption of WWTPs and the specific energy consumption of influent volume and pollutant reduction. Therefore, upgrading and operation with less energy consumption of WWTPs is imperative and the suggestions for Taihu WWTPs based on stringent discharge standard are proposed in detail.

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Cited: WebOfScience(1)
G-CNTs/PVDF mixed matrix membranes with improved antifouling properties and filtration performance
Xiaoyan Guo, Chunyu Li, Chenghao Li, Tingting Wei, Lin Tong, Huaiqi Shao, Qixing Zhou, Lan Wang, Yuan Liao
Front. Environ. Sci. Eng.    2019, 13 (6): 81-.
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A novel nanocomposite OMWCNT-A-GO was synthesized by conjugating OMWCNT and GO.

The P-OMWCNT-A-GO membrane was fabricated by non-solvent induced phase inversion.

The P-OMWCNT-A-GO exhibits the best water flux, BSA rejection and flux recovery.

It should be due to the enhanced membrane pore size, porosity and hydrophilicity.

Although carbon nanomaterials have been widely used as effective nanofillers for fabrication of mixed matrix membranes (MMMs) with outstanding performances, the reproducibility of the fabricated MMMs is still hindered by the non-homogenous dispersion of these carbon nanofillers in membrane substrate. Herein, we report an effective way to improve the compatibility of carbon-based nanomaterials with membrane matrixes. By chemically conjugating the oxidized CNTs (o-CNTs) and GO using hexanediamine as cross-linker, a novel carbon nanohybrid material (G-CNTs) was synthesized, which inherited both the advanced properties of multi-walled carbon nanotubes (CNTs) and graphene oxide (GO). The G-CNTs incorporated polyvinylidene fluoride (PVDF) MMMs (G-CNTs/PVDF) were fabricated via a non-solvent induced phase separation (NIPS) method. The filtration and antifouling performances of G-CNTs/PVDF were evaluated using distillate water and a 1 g/L bovine serum albumin (BSA) aqueous solution under 0.10 MPa. Compared to the MMMs prepared with o-CNTs, GO, the physical mixture of o-CNTs and GO and pure PVDF membrane, the G-CNTs/PVDF membrane exhibited the highest water flux up to 220 L/m2/h and a flux recovery ratio as high as 90%, as well as the best BSA rejection rate. The excellent performances should be attributed to the increased membrane pore size, porosity and hydrophilicity of the resulted membrane. The successful synthesis of the novel nanohybrid G-CNTs provides a new type of nanofillers for MMMs fabrication.

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Cited: WebOfScience(5)
Transmembrane transport of polycyclic aromatic hydrocarbons by bacteria and functional regulation of membrane proteins
Hongqi Wang, Ruhan Jiang, Dekang Kong, Zili Liu, Xiaoxiong Wu, Jie Xu, Yi Li
Front. Environ. Sci. Eng.    2020, 14 (1): 9-.
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• Explaintheadsorption, uptake and transmembrane transport of PAHs by bacteria.

• Analyze functional regulation of membrane proteins inthe transmembrane transport.

• Proteomics technology such as iTRAQ labeling was used to access expressed proteins.

• Single cell analysis technology wereused to study the morphological structure.

In recent years, increasing research has been conducted on transmembrane transport processes and the mechanisms behind the microbial breakdown of polycyclic aromatic hydrocarbons (PAHs), including the role of membrane proteins in transmembrane transport and the mode of transmission. This article explains the adsorption, uptake and transmembrane transport of PAHs by bacteria, the regulation of membrane protein function during the transmembrane transport. There are three different regulation mechanisms for uptake, depending on the state and size of the oil droplets relative to the size of the microbial cells, which are (i) direct adhesion, (ii) emulsification and pseudosolubilization, and (iii) interfacial uptake. Furthermore, two main transmembrane transport modes are introduced, which are (i) active transport and (ii) passive uptake and active efflux mechanism. Meanwhile, introduce the proteomics and single cell analysis technology used to address these areas of research, such as Isobaric tags for relative and absolute quantitation (iTRAQ) technology and Nano Secondary ion mass spectrometry (Nano-SIMS). Additionally, analyze the changes in morphology and structure and the characteristics of microbial cell membranes in the process of transmembrane transport. Finally, recognize the microscopic mechanism of PAHs biodegradation in terms of cell and membrane proteins are of great theoretical and practical significance for understanding the factors that influence the efficient degradation of PAHs contaminants in soil and for remediating the PAHs contamination in this area with biotechnology.

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Screening of textile finishing agents available on the Chinese market: An important source of per- and polyfluoroalkyl substances to the environment
Mehvish Mumtaz, Yixiang Bao, Wenchao Li, Lingxiao Kong, Jun Huang, Gang Yu
Front. Environ. Sci. Eng.    2019, 13 (5): 67-.
Abstract   HTML   PDF (619KB)

Kendrick mass defect was used for PFASs screening in textile finishing agents (TFAs).

Total oxidizable precursor assay provides insight into unknown precursors.

Perfluorooctane sulfonate was found as impurity in short ECF technology based TFAs.

Perfluorooctanoate was also detected in C6 telomerization based TFAs.

Long chain precursors were also observed in both types of TFAs.

Organofluorinated surfactants are widely employed in textile finishing agents (TFAs) to achieve oil, water, and stain repellency. This has been regarded as an important emission source of per-and polyfluoroalkyl substances (PFASs) to the environment. China is the biggest manufacturer of clothes, and thus TFA production is also a relevant industrial activity. Nevertheless, to date, no survey has been conducted on PFAS contents in commercially available TFAs. In the present study, TFA products were investigated by the Kendrick mass defect method. The quantification results demonstrated a significant presence of perfluorooctane sulfonate (0.37 mg/L) in TFAs manufactured by electrochemical fluorination technology. The products obtained by short-chain PFAS-based telomerization were dominated by perfluorooctanoic acid (mean concentration: 0.29 mg/L), whose values exceeded the limits stated in the European Chemical Agency guidelines (0.025 mg/L). Moreover, the total oxidizable precursor assay indicated high levels of indirectly quantified precursors with long alkyl chains (C7–C9). Together, these results suggest that there is currently a certain of environmental and health risks in China that originates from the utilization of TFAs, and a better manufacturing processes are required to reduce such risks.

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Cited: WebOfScience(2)
Biofiltration and disinfection codetermine the bacterial antibiotic resistome in drinking water: A review and meta-analysis
Kun Wan, Wenfang Lin, Shuai Zhu, Shenghua Zhang, Xin Yu
Front. Environ. Sci. Eng.    2020, 14 (1): 10-.
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• Published data was used to analyze the fate of ARGs in water treatment.

• Biomass removal leads to the reduction in absolute abundance of ARGs.

• Mechanism that filter biofilm maintain ARB/ARGs was summarized.

• Potential BAR risks caused by biofiltration and chlorination were proposed.

The bacterial antibiotic resistome (BAR) is one of the most serious contemporary medical challenges. The BAR problem in drinking water is receiving growing attention. In this study, we focused on the distribution, changes, and health risks of the BAR throughout the drinking water treatment system. We extracted the antibiotic resistance gene (ARG) data from recent publications and analyzed ARG profiles based on diversity, absolute abundance, and relative abundance. The absolute abundance of ARG was found to decrease with water treatment processes and was positively correlated with the abundance of 16S rRNA (r2 = 0.963, p<0.001), indicating that the reduction of ARG concentration was accompanied by decreasing biomass. Among treatment processes, biofiltration and chlorination were discovered to play important roles in shaping the bacterial antibiotic resistome. Chlorination exhibited positive effects in controlling the diversity of ARG, while biofiltration, especially granular activated carbon filtration, increased the diversity of ARG. Both biofiltration and chlorination altered the structure of the resistome by affecting relative ARG abundance. In addition, we analyzed the mechanism behind the impact of biofiltration and chlorination on the bacterial antibiotic resistome. By intercepting influent ARG-carrying bacteria, biofilters can enrich various ARGs and maintain ARGs in biofilm. Chlorination further selects bacteria co-resistant to chlorine and antibiotics. Finally, we proposed the BAR health risks caused by biofiltration and chlorination in water treatment. To reduce potential BAR risk in drinking water, membrane filtration technology and water boiling are recommended at the point of use.

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Effects of cultivation strategies on the cultivation of Chlorella sp. HQ in photoreactors
Xiaoya Liu, Yu Hong, Peirui Liu, Jingjing Zhan, Ran Yan
Front. Environ. Sci. Eng.    2019, 13 (5): 78-.
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Heterotrophic cultivation caused high level of ROS and high lipids accumulation.

HMTC is the best culture strategy for improving the microalgal biomass.

Chlorella sp. HQ had great nutrient removal capacity under five culture strategies.

The effects of cultivation strategies (including autotrophic cultivation (AC), heterotrophic cultivation (HC), fed-batch cultivation (FC), heterotrophic+ autotrophic two-stage cultivation (HATC), and heterotrophic+ mixotrophic two-stage cultivation (HMTC)) on the growth and lipid accumulation of Chlorella sp. HQ and its total nitrogen (TN) and total phosphorus (TP) removal in secondary effluent were investigated in column photoreactors. The results showed that the TN and TP removal rates ranged between 93.72%–95.82% and 92.73%–100%, respectively, under the five different strategies. The microalgal growth potential evaluated by the maximal growth rate (Rmax) was in the order of HMTC>HC>FC>AC>HATC. The values of biomass, total lipid yield, triacylglycerols (TAGs) yield, and total lipid content of the microalga cultivated in the last 5 d increased significantly, but the TAGs productivities of the five strategies were lower than those in the first 7 d. Compared with all the other cultivation strategies, the TAGs productivity and yield after 12 d of cultivation under the heterotrophic condition reached the highest values accompanying the highest level of intracellular reactive oxygen species (ROS), in which the TAGs yield reached 40.81 mg/L at the end of the cultivation period. The peaks in TAGs yield and ROS level suggested that HC was beneficial for lipids accumulation via regulating the cellular redox status and exerting ROS stress on microalgal cells. In summary, HMTC was the best cultivation strategy for improving the microalgal biomass and HC was the best strategy for microalgal TAGs accumulation to produce biodiesel.

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Dechlorination of dichlorodiphenyltrichloroethane (DDT) by Fe/Pd bimetallic nanoparticles: Comparison with nZVI, degradation mechanism, and pathways
Kubra Ulucan-Altuntas, Eyup Debik
Front. Environ. Sci. Eng.    2020, 14 (1): 17-.
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• DDT undergoes dechlorination via Fe/Pd bimetallic nanoparticle.

• The oxidation effect of nZVI on DDT is greatly improved when Pd is dopped.

• The highest concentration to be treated under cancerogenesis limit was 110 mg/L.

• The dechlorination of DDT is more like to DDE via Fe/Pd but to DDD via nZVI.

• Degradation products concentrations are lowered via Fe/Pd when compared with nZVI.

In this study, the bimetallic Fe/Pd nanoparticle was synthesized using the catalytic element palladium to increase the effect of nano zero valent iron (nZVI), in the light of the information obtained from our previous study, in which the nZVI synthesis method was modified. Dichlorodiphenyltrichloroethane (DDT), one of the most widely used persistent organic pollutant pesticides in the world, was investigated in terms of its degradation by Fe/Pd nanoparticles and the difference with nZVI was determined. During the study, the Fe/Pd concentration, initial DDT concentration, and contact time were selected as variables affecting the treatment. The highest possible initial DDT concentration for the treatment with Fe/Pd bimetallic nanoparticle was investigated to obtain the DDT effluent concentration below the carcinogenesis limit, 0.23 µg/L. The highest concentration that could be treated was found to be 109.95 mg/L with Fe/Pd. It was found that 44.3 min of contact time and 550 mg/L Fe/Pd concentration were needed to achieve this treatment.

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Review on remediation technologies for arsenic-contaminated soil
Xiaoming Wan, Mei Lei, Tongbin Chen
Front. Environ. Sci. Eng.    2020, 14 (2): 24-.
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• Recent progress of As-contaminated soil remediation technologies is presented.

• Phytoextraction and chemical immobilization are the most widely used methods.

• Novel remediation technologies for As-contaminated soil are still urgently needed.

• Methods for evaluating soil remediation efficiency are lacking.

• Future research directions for As-contaminated soil remediation are proposed.

Arsenic (As) is a top human carcinogen widely distributed in the environment. As-contaminated soil exists worldwide and poses a threat on human health through water/food consumption, inhalation, or skin contact. More than 200 million people are exposed to excessive As concentration through direct or indirect exposure to contaminated soil. Therefore, affordable and efficient technologies that control risks caused by excess As in soil must be developed. The presently available methods can be classified as chemical, physical, and biological. Combined utilization of multiple technologies is also common to improve remediation efficiency. This review presents the research progress on different remediation technologies for As-contaminated soil. For chemical methods, common soil washing or immobilization agents were summarized. Physical technologies were mainly discussed from the field scale. Phytoextraction, the most widely used technology for As-contaminated soil in China, was the main focus for bioremediation. Method development for evaluating soil remediation efficiency was also summarized. Further research directions were proposed based on literature analysis.

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Pollution and biodegradation of hexabromocyclododecanes: A review
Ling Huang, Syed Bilal Shah, Haiyang Hu, Ping Xu, Hongzhi Tang
Front. Environ. Sci. Eng.    2020, 14 (1): 11-.
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• Bioremediation is the most cost-effective approach for degradation of HBCDs.

• Bacteria or bacterial consortia are used in the cases of bio-augmentation.

• Microbes combined with phytoremediation increase the remediation efficiency.

Hexabromocyclododecanes (HBCDs) are the most common brominated flame-retardants after polybrominated diphenyl ethers. HBCDs can induce cancer by causing inappropriate antidiuretic hormone syndrome. Environmental contamination with HBCDs has been detected globally, with concentrations ranging from ng to mg. Methods to degrade HBCDs include physicochemical methods, bioremediation, and phytoremediation. The photodegradation of HBCDs using simulated sunlight or ultraviolet lamps, or chemical catalysts are inefficient and expensive, as is physicochemical degradation. Consequently, bioremediation is considered as the most cost-effective and clean approach. To date, five bacterial strains capable of degrading HBCDs have been isolated and identified: Pseudomonas sp. HB01, Bacillus sp. HBCD-sjtu, Achromobacter sp. HBCD-1, Achromobacter sp. HBCD-2, and Pseudomonas aeruginosa HS9. The molecular mechanisms of biodegradation of HBCDs are discussed in this review. New microbial resources should be explored to increase the resource library in order to identify more HBCD-degrading microbes and functional genes. Synthetic biology methods may be exploited to accelerate the biodegradation capability of existing bacteria, including modification of the degrading strains or functional enzymes, and artificial construction of the degradation microflora. The most potentially useful method is combining micro-degradation with physicochemical methods and phytoremediation. For example, exogenous microorganisms might be used to stimulate the adsorption capability of plants for HBCDs, or to utilize an interaction between exogenous microorganisms and rhizosphere microorganisms to form a new rhizosphere microbial community to enhance the biodegradation and absorption of HBCDs.

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Cited: WebOfScience(1)
Impacts of emissions and meteorological changes on China’s ozone pollution in the warm seasons of 2013 and 2017
Dian Ding, Jia Xing, Shuxiao Wang, Xing Chang, Jiming Hao
Front. Environ. Sci. Eng.    2019, 13 (5): 76-.
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O3 increment is mainly caused by changes in meteorology rather than emissions.

Emission reduction is effective to reduce O3 nationwide, especially in summer.

Strengthened NOx controls are necessary to meet the ambient O3 standard.

We have quantified the impacts of anthropogenic emissions reductions caused by the Air Pollution Control Action Plan and changes in meteorological fields between 2013 and 2017 on the warm-season O3 concentration in China using a regional 3D chemical transport model. We found that the impact on daily maximum eight-hour (MDA8) O3 concentration by the meteorological variation that mostly increased O3 was greater than that from emission reduction, which decreased O3. Specifically, the control measures implemented since 2013 in China have reduced SO2, NOx, PM2.5, and VOC emissions by 33%, 25%, 30%, and 4% in 2017, while NH3 emissions have increased by 7%. The changes in anthropogenic emissions lowered MDA8 O3 by 0.4–3.7 ppb (0.8%–7.6%, varying by region and month), although MDA8 O3 was increased slightly in some urban areas (i.e. North China) at the beginning/end of warm seasons. Relative to 2013, the average 2 m temperature in 2017 shows increments in North, North-east, East, and South China (0.34℃–0.83℃) and decreases in Central China (0.24℃). The average solar radiation shows increments in North, North-east, and South China (7.0–9.7 w/m2) and decreases in Central, South-west, and North-west China (4.7–10.3 w/m2). The meteorological differences significantly change MDA8 O3 by -3.5–8.5 ppb (-8.2%–18.8%) with large temporal variations. The average MDA8 O3 was slightly increased in North, North-east, East, and South China. The response surface model suggests that the O3 formation regime transfers from NOx-saturated in April to NOx-limited in July on average in China.

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Cited: WebOfScience(6)
Oxidant or catalyst for oxidation? The role of manganese oxides in the activation of peroxymonosulfate (PMS)
Jianzhi Huang, Huichun Zhang
Front. Environ. Sci. Eng.    2019, 13 (5): 65-null.
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Manganese oxides (MnOx) have been demonstrated to be effective materials to activate Oxone (i.e., PMS) to degrade various contaminants. However, the contribution of direct oxidation by MnOx to the total contaminant degradation under acidic conditions was often neglected in the published work, which has resulted in different and even conflicting interpretations of the reaction mechanisms. Here, the role of MnOx (as both oxidants and catalysts) in the activation of Oxone was briefly discussed. The findings offered new insights into the reaction mechanisms in PMS-MnOx and provided a more accurate approach to examine contaminant degradation for water/wastewater treatment.

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Cited: WebOfScience(4)
Enhanced activation of peroxymonosulfate by CNT-TiO2 under UV-light assistance for efficient degradation of organic pollutants
Xuemin Hao, Guanlong Wang, Shuo Chen, Hongtao Yu, Xie Quan
Front. Environ. Sci. Eng.    2019, 13 (5): 77-.
Abstract   HTML   PDF (1814KB)

CNT-TiO2 composite is used to activate PMS under UV-light assistance.

Superior performance is due to the enhanced electron-transfer ability of CNT.

SO4, •OH and 1O2 play key roles in the degradation of organic pollutants.

In this work, a UV-light assisted peroxymonosulfate (PMS) activation system was constructed with the composite catalyst of multi-walled carbon nanotubes (CNT) - titanium dioxide (TiO2). Under the UV light irradiation, the photoinduced electrons generated from TiO2 could be continuously transferred to CNT for the activation of PMS to improve the catalytic performance of organic pollutant degradation. Meanwhile, the separation of photoinduced electron-hole pairs could enhance the photocatalysis efficiency. The electron spin resonance spectroscopy (EPR) and quenching experiments confirmed the generation of sulfate radical (SO4), hydroxyl radical (•OH) and singlet oxygen (1O2) in the UV/PMS/20%CNT-TiO2 system. Almost 100% phenol degradation was observed within 20 min UV-light irradiation. The kinetic reaction rate constant of the UV/PMS/20%CNT-TiO2 system (0.18 min1) was 23.7 times higher than that of the PMS/Co3O4 system (0.0076 min1). This higher catalytic performance was ascribed to the introduction of photoinduced electrons, which could enhance the activation of PMS by the transfer of electrons in the UV/PMS/CNT-TiO2 system.

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Cited: WebOfScience(5)
Trophic mode and organics metabolic characteristic of fungal community in swine manure composting
Jing Peng, Ke Wang, Xiangbo Yin, Xiaoqing Yin, Mengfei Du, Yingzhi Gao, Philip Antwi, Nanqi Ren, Aijie Wang
Front. Environ. Sci. Eng.    2019, 13 (6): 93-.
Abstract   HTML   PDF (2055KB)

Fungal trophic modes and substrates utilization ability was observed in composting.

Fungi had the higher diversity and more trophic types in thermophilic phase.

Fungi had the higher metabolic potential in fresh swine manure and mature production.

Redox potential, organics and moisture are main factors impacting fungal community.

Composting reduced pathogenic fungi and enrich dung saprotroph fungi in swine manure.

The succession of fungal community, trophic mode and metabolic characteristics were evaluated in 60 days composting of swine manure by high-throughput sequencing, FUNGuild and Biolog method, respectively. The result showed that the fungal community diversity reached to the highest level (76 OTUs) in the thermophilic phase of composting, then sustained decline to 15 OTUs after incubation. There were 10 fungal function groups in the raw swine manure. Pathotroph-saprotroph fungi reached to 15.91% on Day-10 but disappeared on Day-60. Dung saprotroph-undefined saprotroph fungi grown from 0.19% to 52.39% during the treatment. The fungal community had more functional groups but the lower substrate degradation rates in the thermophilic phase. The fungal communities on Day-0 and Day-60 had the highest degradation rates of amino acids and polymers, respectively. Redundancy analysis showed that ORP (49.6%), VS/Ash (45.3%) and moisture (39.2%) were the main influence factors on the succession of fungal community in the swine manure composting process.

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FESE’s Best Papers of 2019
Front. Environ. Sci. Eng.    2020, 14 (3): 55-null.
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Rapid control of black and odorous substances from heavily-polluted sediment by oxidation: Efficiency and effects
Kun Li, Min Yang, Jianfeng Peng, Ruiping Liu, Tista Prasai Joshi, Yaohui Bai, Huijuan Liu
Front. Environ. Sci. Eng.    2019, 13 (6): 87-.
Abstract   HTML   PDF (1249KB)

Oxidants were proposed to rapidly control black and odorous substances in sediments.

NaClO and KMnO4 had excellent efficiency to remove black and odorous substances.

NaClO dramatically accelerated the release of organics, NH4+-N, P, and heavy-metals.

Moderate oxidation had a limited effect on microbial communities.

NaClO of 0.2 mmol/g was viewed to be the optimum option.

The control of black and odorous substances in sediments is of crucial importance to improve the urban ecological landscape and to restore water environments accordingly. In this study, chemical oxidation by the oxidants NaClO, H2O2, and KMnO4 was proposed to achieve rapid control of black and odorous substances in heavily-polluted sediments. Results indicate that NaClO and KMnO4 are effective at removing Fe(II) and acid volatile sulfides. The removal efficiencies of Fe(II) and AVS were determined to be 45.2%, 94.1%, and 93.7%, 89.5% after 24-h exposure to NaClO and KMnO4 at 0.2 mmol/g, respectively. Additionally, rapid oxidation might accelerate the release of pollutants from sediment. The release of organic matters and phosphorus with the maximum ratios of 22.1% and 51.2% was observed upon NaClO oxidation at 0.4 mmol/g. Moreover, the introduction of oxidants contributed to changes in the microbial community composition in sediment. After oxidation by NaClO and KMnO4 at 0.4 mmol/g, the Shannon index decreased from 6.72 to 5.19 and 4.95, whereas the OTU numbers decreased from 2904 to 1677 and 1553, respectively. Comparatively, H2O2 showed a lower effect on the removal of black and odorous substances, pollutant release, and changes in sediment microorganisms. This study illustrates the effects of oxidant addition on the characteristics of heavily polluted sediments and shows that chemical oxidants may be an option to achieve rapid control of black and odorous substances prior to remediation of water environments.

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Identifying human-induced influence on microbial community: A comparative study in the effluent-receiving areas in Hangzhou Bay
Yuhan Zheng, Zhiguo Su, Tianjiao Dai, Feifei Li, Bei Huang, Qinglin Mu, Chuanping Feng, Donghui Wen
Front. Environ. Sci. Eng.    2019, 13 (6): 90-.
Abstract   HTML   PDF (1230KB)

Microbial compositions showed high differences in two study areas.

COD was the key anthropogenic indicator in the coastal wastewater disposal area.

Distinctive microbes capable of degrading toxic pollutants were screened.

Microbial communities in effluent-receiving areas followed “niche theory”.

Microbial community structure is affected by both natural processes and human activities. In coastal area, anthropegenetic activity can usually lead to the discharge of the effluent from wastewater treatment plant (WWTP) to sea, and thus the water quality chronically turns worse and marine ecosystem becomes unhealthy. Microorganisms play key roles in pollutants degradation and ecological restoration; however, there are few studies about how the WWTP effluent disposal influences coastal microbial communities. In this study, sediment samples were collected from two WWTP effluent-receiving areas (abbreviated as JX and SY) in Hangzhou Bay. First, based on the high-throughput sequencing of 16S rRNA gene, microbial community structure was analyzed. Secondly, several statistical analyses were conducted to reveal the microbial community characteristics in response to the effluent disposal. Using PCoA, the significant difference of in microbial community structure was determined between JX and SY; using RDA, water COD and temperature, and sediment available phosphate and ammonia nitrogen were identified as the key environmental factors for the community difference; using LDA effect size analysis, the most distinctive microbes were found and their correlations with environmental factors were investigated; and according to detrended beta-nearest-taxon-index, the sediment microbial communities were found to follow “niche theory”. An interesting and important finding was that in SY that received more and toxic COD, many distinctive microbes were related to the groups that were capable of degrading toxic organic pollutants. This study provides a clear illustration of eco-environmental deterioration under the long-term human pressure from the view of microbial ecology.

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Influence of phosphate on deposition and detachment of TiO2 nanoparticles in soil
Zhan Wang, Chongyang Shen, Yichun Du, Yulong Zhang, Baoguo Li
Front. Environ. Sci. Eng.    2019, 13 (5): 79-.
Abstract   HTML   PDF (909KB)

We examined influence of phosphate on transport of TiO2 NPs in soil.

Deposition was reduced at higher pH and by adsorption of phosphate in soil.

Release was more for NPs initially deposited at higher pH.

Release was more for NPs initially deposited in the presence of phosphate.

Surface roughness and charge heterogeneity play a role in the deposition/ release.

The widespread use of TiO2 nanoparticles (NPs) makes inevitable their release into the soil. Phosphate is also widespread within soil, and is likely copresent with TiO2 NPs. However, the influence of phosphate on deposition/release— and thereby on transport— of TiO2 NPs in soil is yet to be elucidated. In this study we conducted saturated column experiments to systematically examine the transport of TiO2 NPs in soil amended with phosphate at different ionic strengths (ISs) (1, 10, 100 mmol/L NaCl) and pHs (4 and 9). Results show that the deposition of TiO2 NPs decreased with decreasing IS, increasing pH, and when soil absorbed phosphate. These observations are qualitatively in agreement with Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy calculations, because the repulsive energy barrier is larger and secondary minimum depth is smaller at a lower IS, higher pH, and in the presence of phosphate. Accordingly, both primary- and secondary-minimum deposition were inhibited. Interestingly, although the deposition was less at higher pH and in the presence of phosphate, the subsequent spontaneous detachment and detachment by reduction of solution IS in these cases were greater. In addition, the presence of phosphate in the solution can cause a small quantity of attached TiO2 NPs to detach, even without perturbations of physical and chemical conditions. Our study was the first to investigate the influence of phosphate on detachment of TiO2 NPs and the results have important implication for accurate prediction of fate and transport of TiO2 NPs in subsurface environments.

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Cited: WebOfScience(3)
Quantification of pesticide residues on plastic mulching films in typical farmlands of the North China
Baoyuan Guo, Jiao Meng, Xinyu Wang, Chengnan Yin, Weiyu Hao, Baiwen Ma, Zhang Tao
Front. Environ. Sci. Eng.    2020, 14 (1): 2-.
Abstract   HTML   PDF (810KB)

• Pesticide residuals on mulching film of Shandong, Tianjin and Hebei.

• Detected 29 pesticides in soil and 30 in mulching film.

• Pesticides on plastic films: 86.4‒22213.2 ng/g and in soil: 9.3‒535.3 ng/g.

• Pesticides on plastic films 20 times higher than in soil.

Plastic debris as new pollutants attracts much attention in the recent years. The plastic mulching films is one of the most important plastic debirs source in the environment. The aim of this work was to investigate the current status of pesticide residues on the plastic mulching films. Based on the QuEChERS method, multi-residue methods for detection of pesticide residues with gas chromatography tandem mass spectrum (GC-MS) and high performance liquid chromatography tandem mass spectrum (HPLC-MS) were developed for the analysis of the pesticides residues in plastic film and soil samples from Tianjin, Hebei and Shandong. The total concentrations of pesticide residues were in the range of 86.4‒22213.2 ng/g in plastic film debris, which was about 20 times higher than that in soil (9.3‒535.3 ng/g). Residual level of pesticides varied greatly in different samples. The historical usage and recent application of pesticides were the main sources for pesticide residues on plastic films and soil. In short, plastic mulching films could act as a sink for pesticides in farmland and the ubiquitous pesticide residues on plastic films should draw more attention.

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Bacterial inactivation, DNA damage, and faster ATP degradation induced by ultraviolet disinfection
Chao Yang, Wenjun Sun, Xiuwei Ao
Front. Environ. Sci. Eng.    2020, 14 (1): 13-.
Abstract   HTML   PDF (740KB)

• Long amplicon is more effective to test DNA damage induced by UV.

• ATP in bacteria does not degrade instantly but does eventually after UV exposure.

• After medium pressure UV exposure, ATP degraded faster.

The efficacy of ultraviolet (UV) disinfection has been validated in numerous studies by using culture-based methods. However, the discovery of viable but non-culturable bacteria has necessitated the investigation of UV disinfection based on bacterial viability parameters. We used quantitative polymerase chain reaction (qPCR) to investigate DNA damage and evaluated adenosine triphosphate (ATP) to indicate bacterial viability. The results of qPCR effectively showed the DNA damage induced by UV when using longer gene amplicons, in that sufficiently long amplicons of both 16S and gadA indicated that the UV induced DNA damages. The copy concentrations of the long amplicons of 16S and gadA decreased by 2.38 log/mL and 1.88 log/mL, respectively, after exposure to 40 mJ/cm2 low-pressure UV. After UV exposure, the ATP level in the bacteria did not decrease instantly. Instead it decreased gradually at a rate that was positively related to the UV fluence. For low-pressure UV, this rate of decrease was slow, but for medium pressure UV, this rate of decrease was relatively high when the UV fluence reached 40 mJ/cm2. At the same UV fluence, the ATP level in the bacteria decreased at a faster rate after exposure to medium-pressure UV.

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Cited: WebOfScience(1)
Anaerobic phenanthrene biodegradation with four kinds of electron acceptors enriched from the same mixed inoculum and exploration of metabolic pathways
Zuotao Zhang, Chongyang Wang, Jianzhong He, Hui Wang
Front. Environ. Sci. Eng.    2019, 13 (5): 80-.
Abstract   HTML   PDF (1437KB)

Anaerobic phenanthrene biodegradation enriched process was described in detail.

The enriched bacterial communities were characterized under four redox conditions.

The enriched archaeal communities were stated under high percentage conditions.

Relatively intact pathways of anaerobic phenanthrene biodegradation were proposed.

Polycyclic aromatic hydrocarbons (PAHs) are widespread and persistent contaminants worldwide, especially in environments devoid of molecular oxygen. For lack of molecular oxygen, researchers enhanced anaerobic zones PAHs biodegradation by adding sulfate, bicarbonate, nitrate, and iron. However, microbial community reports of them were limited, and information of metabolites was poor except two-ring PAH, naphthalene. Here, we reported on four phenanthrene-degrading enrichment cultures with sulfate, bicarbonate, nitrate, and iron as electron acceptors from the same initial inoculum. The high-to-low order of the anaerobic phenanthrene biodegradation rate was the nitrate-reducing conditions>sulfate-reducing conditions>methanogenic conditions>iron-reducing conditions. The dominant bacteria populations were Desulfobacteraceae, Anaerolinaceae, and Thermodesulfobiaceae under sulfate-reducing conditions; Moraxellaceae, Clostridiaceae, and Comamonadaceae under methanogenic conditions; Rhodobacteraceae, Planococcaceae, and Xanthomonadaceae under nitrate-reducing conditions; and Geobacteraceae, Carnobacteriaceae, and Anaerolinaceae under iron-reducing conditions, respectively. Principal component analysis (PCA) indicated that bacteria populations of longtime enriched cultures with four electron acceptors all obtained significant changes from original inoculum, and bacterial communities were similar under nitrate-reducing and iron-reducing conditions. Archaea accounted for a high percentage under iron-reducing and methanogenic conditions, and Methanosarcinaceae and Methanobacteriaceae, as well as Methanobacteriaceae, were the dominant archaea populations under iron-reducing and methanogenic conditions. The key steps of phenanthrene biodegradation under four reducing conditions were carboxylation, further ring system reduction, and ring cleavage.

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Cited: WebOfScience(2)
In situ formation of bimetallic FeNi nanoparticles on sand through green technology: Application for tetracycline removal
Ravikumar KVG, Debayan Ghosh, Mrudula Pulimi, Chandrasekaran Natarajan, Amitava Mukherjee
Front. Environ. Sci. Eng.    2020, 14 (1): 16-.
Abstract   HTML   PDF (1478KB)

• In situ preparation of FeNi nanoparticles on the sand via green synthesis approach.

• Removal of tetracycline using GS-FeNi in batch and column study.

• Both reductive degradation and sorption played crucial role the process.

• Reusability of GS-FeNi showed about 77.39±4.3% removal on 4th cycle.

• TC by-products after interaction showed less toxic as compared with TC.

In this study, FeNi nanoparticles were green synthesized using Punica granatum (pomegranate) peel extract, and these nanoparticles were also formed in situ over quartz sand (GS-FeNi) for removal of tetracycline (TC). Under the optimized operating conditions, (GS-FeNi concentration: 1.5% w/v; concentration of TC: 20 mg/L; interaction period: 180 min), 99±0.2% TC removal was achieved in the batch reactor. The removal capacity was 181±1 mg/g. A detailed characterization of the sorbent and the solution before and after the interaction revealed that the removal mechanism(s) involved both the sorption and degradation of TC. The reusability of reactant was assessed for four cycles of operation, and 77±4% of TC removal was obtained in the cycle. To judge the environmental sustainability of the process, residual toxicity assay of the interacted TC solution was performed with indicator bacteria (Bacillus and Pseudomonas) and algae (Chlorella sp.), which confirmed a substantial decrease in the toxicity. The continuous column studies were undertaken in the packed bed reactors using GS-FeNi. Employing the optimized conditions, quite high removal efficiency (978±5 mg/g) was obtained in the columns. The application of GS-FeNi for antibiotic removal was further evaluated in lake water, tap water, and ground water spiked with TC, and the removal capacity achieved was found to be 781±5, 712±5, and 687±3 mg/g, respectively. This work can pave the way for treatment of antibiotics and other pollutants in the reactors using novel green composites prepared from fruit wastes.

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Pesticide wastewater treatment using the combination of the microbial electrolysis desalination and chemical-production cell and Fenton process
Songwei Lin, Yaobin Lu, Bo Ye, Cuiping Zeng, Guangli Liu, Jieling Li, Haiping Luo, Renduo Zhang
Front. Environ. Sci. Eng.    2020, 14 (1): 12-.
Abstract   HTML   PDF (1819KB)

• MEDCC combined with Fenton process was developed to treat real pesticide wastewater.

• Pesticide removal was attributable to desalination in the MEDCC.

• High COD removal was attributable to organic distributions in different chambers.

The combination of the microbial electrolysis desalination and chemical-production cell (MEDCC) and Fenton process for the pesticide wastewater treatment was investigate in this study. Real wastewater with several toxic pesticides, 1633 mg/L COD, and 200 in chromaticity was used for the investigation. Results showed that desalination in the desalination chamber of MEDCC reached 78%. Organics with low molecular weights in the desalination chamber could be removed from the desalination chamber, resulting in 28% and 23% of the total COD in the acid-production and cathode chambers, respectively. The desalination in the desalination chamber and organic transfer contributed to removal of pesticides (e.g., triadimefon), which could not be removed with other methods, and of the organics with low molecular weights. The COD in the effluent of the MEDCC combined the Fenton process was much lower than that in the perixo-coagulaiton process (<150 vs. 555 mg/L). The combined method consumed much less energy and acid for the pH adjustment than that the Fenton.

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Cited: WebOfScience(1)
A newly defined dioxygenase system from Mycobacterium vanbaalenii PYR-1 endowed with an enhanced activity of dihydroxylation of high-molecular-weight polyaromatic hydrocarbons
Yiquan Wu, Ying Xu, Ningyi Zhou
Front. Environ. Sci. Eng.    2020, 14 (1): 14-.
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Mycobacterium vanbaalenii PYR-1 utilizes PAHs at different rates.

• Both NidA3B3 and FNidA3B3 catalyze high-molecular-weight PAHs dihydroxylation.

• NidA3B3 shows an enhanced activity with an endogenous electron transport chain.

• FNidA3B3 has an enhanced activity by 50% approximately compared with NidA3B3.

• FNidA3B3/NidA3B3 and NidAB in the same strain come from different ancestors.

NidA3B3 is a terminal dioxygenase whose favorable substrates are high-molecular-weight polyaromatic hydrocarbons (PAHs) from Mycobacterium vanbaalenii PYR-1, a powerful PAHs degradation strain. NidA3B3 was reported to incorporate a dioxygen into the benzene ring of PAHs when equipped with an exogenous electron transport chain components PhdCD from Nocardioides sp. strain KP7 by biotransformation, but this enzyme system was not particularly efficient. In this study, strain PYR-1 was confirmed to utilize four different PAHs at different growth rates. When PhtAcAd, an endogenous electron transport chain of a phthalate dioxygenase system, was substituted for PhdCD to couple with NidA3B3, the specific activity to convert phenanthrene by strain BL21(DE3) [pNidA3B3-PhAcAd] was 0.15±0.03 U/mg, but the specific activity of strain BL21(DE3) [pNidA3B3-PhdCD] was only 0.025±0.006 U/mg. In addition, FNidA3, encoded by a newly defined ORF, has a prolonged 19-amino acid sequence at the N-terminal compared with NidA3. FNidA3B3 increased the activity by 50% approximately than NidA3B3 when using PhtAcAd. Components of the electron transport chain PhtAc and PhtAd were purified and characterized. The Km, kcat, kcat/Km values of the PhtAd were 123±26.9 M, 503±49.9 min1, 4.1 M1·min1, respectively. And the Km, kcat, kcat/Km values of the ferredoxin PhtAc were 52.5±9.7 M, 3.8±0.19 min1 and 0.07 M1·min1, respectively. Basing on the phylogenetic analysis, NidA3/FNidA3 were far from its isoenzyme NidA from the same strain. Combining their primary differences of transcriptional pattern in vivo, it indicated that the functionally similar Rieske dioxygenases NidA3B3/FNidA3B3 and NidAB might originate from different ancestors.

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