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1.
Evaluating acute toxicity in enriched nitrifying cultures: Lessons learned.
Lopez, C, Knapp, CW
Journal of microbiological methods. 2022;:106377
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Abstract
Toxicological batch assays are essential to assess a compound's acute effect on microorganisms. This methodology is frequently employed to evaluate the effect of contaminants in sensitive microbial communities from wastewater treatment plants (WWTPs), such as autotrophic nitrifying populations. However, despite nitrifying batch assays being commonly mentioned in the literature, their experimental design criteria are rarely reported or overlooked. Here, we found that slight deviations in culture preparations and conditions impacted bacterial community performance and could skew assay results. From pre-experimental trials and experience, we determined how mishandling and treatment of cultures could affect nitrification activity. While media and biomass preparations are needed to establish baseline conditions (e.g., biomass washing), we found extensive centrifugation selectively destabilised nitrification activities. Further, it is paramount that the air supply is adjusted to minimise nitrite build-up in the culture and maintain suitable aeration levels without sparging ammonia. DMSO and acetone up to 0.03% (v/v) were suitable organic solvents with minimal impact on nitrification activity. In the nitrification assays with allylthiourea (ATU), dilute cultures exhibited more significant inhibition than concentrated cultures. So there were biomass-related effects; however, these differences minimally impacted the EC50 values. Using different nutrient-media compositions had a minimal effect; however, switching mineral media for the toxicity test from the original cultivation media is not recommended because it reduced the original biomass nitrification capacity. Our results demonstrated that these factors substantially impact the performance of the nitrifying inoculum used in acute bioassays, and consequently, affect the response of AOB-NOB populations during the toxicant exposure. These are not highlighted in operation standards, and unfortunately, they can have significant consequential impacts on the determinations of toxicological endpoints. Moreover, the practical procedures tested here could support other authors in developing testing methodologies, adding quality checks in the experimental framework with minimal waste of time and resources.
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2.
One-pot fabrication of lignin-based aromatic porous polymers for efficient removal of bisphenol AF from water.
Sun, L, Chai, K, Zhou, L, Liao, D, Ji, H
International journal of biological macromolecules. 2021;:396-405
Abstract
To remove the bisphenol AF (BPAF) from aqueous solution, two different types of lignin-based aromatic porous polymers (LAPP-1 and LAPP-2) were fabricated via one-pot crosslinking of lignin with 1,4-dichloroxylene and 4,4'-bis(chloromethyl)-1,1'-biphenyl, respectively. The successful synthesis of LAPPs was confirmed by FTIR and XPS, SEM, TEM and N2 adsorption-desorption analysis. Then, batch adsorption experiments were conducted to investigate adsorption properties toward BPAF. Based on the results, the adsorption processes were in accordance with the pseudo-second-order kinetic model and the Freundlich isotherm model, and the thermodynamic studies showed that the adsorption was a spontaneous and exothermic process. It is remarkable that LAPPs exhibited good adsorption performance in wide ranges of pH and ionic strength as well as in recycling process. Notably, compared to LAPP-1, LAPP-2 exhibited higher adsorption capacity for BPAF, which can be ascribed to its higher porosity and content of aromatic ring. Moreover, the comprehensive analysis of experimental and theoretical results indicated that the π-π interactions and pore adsorption may jointly drive the uptake process of BPAF. Considering the simple fabrication method employed and excellent BPAF adsorption performance, LAPPs provided new insights into the development of advanced lignin-based adsorbents for removal of BPAF from water.
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3.
Boron nitride-based materials for water purification: Progress and outlook.
Ihsanullah, I
Chemosphere. 2021;:127970
Abstract
Analogous to the carbon family, boron nitride (BN)-based materials have gained considerable attention in recent times for applications in various fields. Owing to their extraordinary characteristics, i.e., high surface area, low density, superior thermal stability, mechanical strength, and conductivity, excellent corrosion, and oxidation resistance, the BN nanomaterials have been explored in water remediation. This article critically evaluates the latest development in applications of BN-based materials in water purification with focus on adsorption, synthesis of novel membranes and photocatalytic degradation of pollutants. The adsorption of various noxious pollutants, i.e., dyes, organic compounds, antibiotics, and heavy metals from aqueous medium BN-based materials are described in detail by illustrating the adsorption mechanism and regeneration potential. The major hurdles and opportunities related to the synthesis and water purification applications of BN-based materials are underscored. Finally, a roadmap is suggested for future research to assure the effective applications of BN-based materials in water purification. This review is beneficial in understanding the current status of these unique materials in water purification and accelerating the research focusing their future water remediation applications.
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4.
Biomedical Applications of Biomolecules Isolated from Methanotrophic Bacteria in Wastewater Treatment Systems.
Salem, R, ElDyasti, A, Audette, GF
Biomolecules. 2021;(8)
Abstract
Wastewater treatment plants and other remediation facilities serve important roles, both in public health, but also as dynamic research platforms for acquiring useful resources and biomolecules for various applications. An example of this is methanotrophic bacteria within anaerobic digestion processes in wastewater treatment plants. These bacteria are an important microbial source of many products including ectoine, polyhydroxyalkanoates, and methanobactins, which are invaluable to the fields of biotechnology and biomedicine. Here we provide an overview of the methanotrophs' unique metabolism and the biochemical pathways involved in biomolecule formation. We also discuss the potential biomedical applications of these biomolecules through creation of beneficial biocompatible products including vaccines, prosthetics, electronic devices, drug carriers, and heart stents. We highlight the links between molecular biology, public health, and environmental science in the advancement of biomedical research and industrial applications using methanotrophic bacteria in wastewater treatment systems.
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5.
Cyanobacterial blooms in wastewater treatment facilities: Significance and emerging monitoring strategies.
Romanis, CS, Pearson, LA, Neilan, BA
Journal of microbiological methods. 2021;:106123
Abstract
Municipal wastewater treatment facilities (WWTFs) are prone to the proliferation of cyanobacterial species which thrive in stable, nutrient-rich environments. Dense cyanobacterial blooms frequently disrupt treatment processes and the supply of recycled water due to their production of extracellular polymeric substances, which hinder microfiltration, and toxins, which pose a health risk to end-users. A variety of methods are employed by water utilities for the identification and monitoring of cyanobacteria and their toxins in WWTFs, including microscopy, flow cytometry, ELISA, chemoanalytical methods, and more recently, molecular methods. Here we review the literature on the occurrence and significance of cyanobacterial blooms in WWTFs and discuss the pros and cons of the various strategies for monitoring these potentially hazardous events. Particular focus is directed towards next-generation metagenomic sequencing technologies for the development of site-specific cyanobacterial bloom management strategies. Long-term multi-omic observations will enable the identification of indicator species and the development of site-specific bloom dynamics models for the mitigation and management of cyanobacterial blooms in WWTFs. While emerging metagenomic tools could potentially provide deep insight into the diversity and flux of problematic cyanobacterial species in these systems, they should be considered a complement to, rather than a replacement of, quantitative chemoanalytical approaches.
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6.
Optimizing Adsorption of 17α-Ethinylestradiol from Water by Magnetic MXene Using Response Surface Methodology and Adsorption Kinetics, Isotherm, and Thermodynamics Studies.
Xu, M, Huang, C, Lu, J, Wu, Z, Zhu, X, Li, H, Xiao, L, Luo, Z
Molecules (Basel, Switzerland). 2021;(11)
Abstract
Magnetic MXene composite Fe3O4@Ti3C2 was successfully prepared and employed as 17α-ethinylestradiol (EE2) adsorbent from water solution. The response surface methodology was employed to investigate the interactive effects of adsorption parameters (adsorption time, pH of the solution, initial concentration, and the adsorbent dose) and optimize these parameters for obtaining maximum adsorption efficiency of EE2. The significance of independent variables and their interactions were tested by the analysis of variance (ANOVA) and t-test statistics. Optimization of the process variables for maximum adsorption of EE2 by Fe3O4@Ti3C2 was performed using the quadratic model. The model predicted maximum adsorption of 97.08% under the optimum conditions of the independent variables (adsorption time 6.7 h, pH of the solution 6.4, initial EE2 concentration 0.98 mg L-1, and the adsorbent dose 88.9 mg L-1) was very close to the experimental value (95.34%). pH showed the highest level of significance with the percent contribution (63.86%) as compared to other factors. The interactive influences of pH and initial concentration on EE2 adsorption efficiency were significant (p < 0.05). The goodness of fit of the model was checked by the coefficient of determination (R2) between the experimental and predicted values of the response variable. The response surface methodology successfully reflects the impact of various factors and optimized the process variables for EE2 adsorption. The kinetic adsorption data for EE2 fitted well with a pseudo-second-order model, while the equilibrium data followed Langmuir isotherms. Thermodynamic analysis indicated that the adsorption was a spontaneous and endothermic process. Therefore, Fe3O4@Ti3C2 composite present the outstanding capacity to be employed in the remediation of EE2 contaminated wastewaters.
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7.
Heterogeneous Fenton catalysts: A review of recent advances.
Thomas, N, Dionysiou, DD, Pillai, SC
Journal of hazardous materials. 2021;(Pt B):124082
Abstract
Heterogeneous Fenton catalysts are emerging as excellent materials for applications related to water purification. In this review, recent trends in the synthesis and application of heterogeneous Fenton catalysts for the abatement of organic pollutants and disinfection of microorganisms are discussed. It is noted that as the complexity of cell wall increases, the resistance level towards various disinfectants increases and it requires either harsh conditions or longer exposure time for the complete disinfection. In case of viruses, enveloped viruses (e.g. SARS-CoV-2) are found to be more susceptible to disinfectants than the non-enveloped viruses. The introduction of plasmonic materials with the Fenton catalysts broadens the visible light absorption efficiency of the hybrid material, and incorporation of semiconductor material improves the rate of regeneration of Fe(II) from Fe(III). A special emphasis is given to the use of Fenton catalysts for antibacterial applications. Composite materials of magnetite and ferrites remain a champion in this area because of their easy separation and reuse, owing to their magnetic properties. Iron minerals supported on clay materials, perovskites, carbon materials, zeolites and metal-organic frameworks (MOFs) dramatically increase the catalytic degradation rate of contaminants by providing high surface area, good mechanical stability, and improved electron transfer. Moreover, insights to the zero-valent iron and its capacity to remove a wide range of organic pollutants, heavy metals and bacterial contamination are also discussed. Real world applications and the role of natural organic matter are summarised. Parameter optimisation (e.g. light source, dosage of catalyst, concentration of H2O2 etc.), sustainable models for the reusability or recyclability of the catalyst and the theoretical understanding and mechanistic aspects of the photo-Fenton process are also explained. Additionally, this review summarises the opportunities and future directions of research in the heterogeneous Fenton catalysis.
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8.
Ozonation of 47 organic micropollutants in secondary treated municipal effluents: Direct and indirect kinetic reaction rates and modelling.
Mathon, B, Coquery, M, Liu, Z, Penru, Y, Guillon, A, Esperanza, M, Miège, C, Choubert, JM
Chemosphere. 2021;:127969
Abstract
Micropollutants like pharmaceuticals, hormones and pesticides are still found in treated municipal wastewater. An effective way to degrade micropollutants is to use oxidants such as ozone or hydroxyl radicals. We designed an innovative experimental protocol combining batch experiments and a study of a full-scale WWTP to understand and predict the removal via ozonation of typical micropollutants present in secondary treated effluents. First, the direct and indirect ozonation of 47 organic micropollutants was scrutinized, then a model was developed and calibrated to simulate the ozone transfers and the oxidation of the selected micropollutants. The kinetic rate constants between micropollutants and ozone or hydroxyl radicals (OH●) were determined for 47 micropollutants found in secondary treated effluent. We classified the micropollutants into low- (kO3 between 1.50 and 4.47 × 102 L mol-1. s-1), medium- (kO3 between 1.31 × 103 and 4.92 × 103 L mol-1. s-1) and high-oxidizable groups (kO3 between 9.44 × 104 and 8.18 × 106 L mol-1. s-1) according to their reactivity with ozone, and identified the major degradation pathways for all 47 micropollutants. Micropolluants of the low- and medium-oxidizable groups were largely eliminated by the indirect pathway, at 96% and 84% on average, respectively. In contrast, micropollutants of high-oxidizable group were largely eliminated by the direct pathway, at 98% on average. The model successfully simulated the direct and indirect ozonation of the 47 micropollutants in batch experiments and confirmed the predominant pathways for each group. Finally, the model was applied to the full-scale ozonation process operated at an ozone dose ranging from 0.5 to 1.6 gO3. gDOC-1. The model was found to reliably simulate the ozonation-process removal efficiencies for 4 micropollutants (imidacloprid, fenofibric acid, metronidazole and ketoprofen).
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9.
Electro-Fenton with peroxi-coagulation as a feasible pre-treatment for high-strength refractory coke plant wastewater: Parameters optimization, removal behavior and kinetics analysis.
Zhou, X, Hou, Z, Lv, L, Song, J, Yin, Z
Chemosphere. 2020;:124649
Abstract
Electro-Fenton (EF) with peroxi-coagulation (PC) as an emerging electro-chemical advanced oxidation method has been extensively applied to treat refractory wastewater. However, the studies on the pretreatment of the raw coke plant wastewater by EF process were still lacking. In this study, a lab-scale EF system (Fe as anode and graphite as cathode) achieved the highest COD removal of 69.2% based on the preliminary experiments. The process parameters and corresponding COD removal performance were further optimized using response surface methodology (RSM) combined with Box-Behnken experimental design (BBD). The optimal conditions were obtained as: 3.2 mA cm-2 of current density, 2 h of the reaction time and 2.6 of the initial pH value, with the COD removal reaching 70.0%. Fourier infrared (FTIR), fluorescence excitation-emmission matrix (EEM) and gas chromatography-mass spectrometry (GC-MS) also revealed the degradation behaviors of dissolved organic matters (DOMs) by characterizing their structures and compositions before and after EF pretreatment, thus greatly improving the biodegradability of the wastewater. Moreover, the EF process for COD removal well followed third-order kinetics model. These findings give helpful guidance to design, optimize and control the EF process as a favourable pretreatment for actual refractory coking wastewater in practice.
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10.
Highly efficient removal of organic pollutants via a green catalytic oxidation system based on sodium metaborate and peroxymonosulfate.
Rao, L, Yang, Y, Chen, L, Liu, X, Chen, H, Yao, Y, Wang, W
Chemosphere. 2020;:124687
Abstract
The development of highly efficient and green catalytic oxidation process based on peroxymonosulfate (PMS) activation has been identified to be a significant yet challenging objective in the environmental catalysis field. A simple, environmentally benign and highly effective catalytic oxidation system was innovatively constructed by coupling NaBO2 and PMS for the removal of Acid Red 1. The catalytic mechanism in the NaBO2/PMS system was elucidated by electron paramagnetic resonance (EPR) combined with several radical capture reagents (ascorbic acid, methanol, tert-butyl alcohol, ethanol and l-histidine). The experimental results indicated that singlet oxygen (1O2) severed as the predominant reactive oxygen species (ROS) rather than the HO or during the catalytic oxidation process, at variance with the reported radical pathway in the Co2+/PMS system. Inspiringly, p-benzoquinone (p-BQ) as a trapping agent in most advanced oxidation process could be turned into the positive one in the NaBO2/PMS system, achieving a nearly 3-times enhancement in terms of the rate constant for AR1 removal. More interestingly, sodium chloride (NaCl) presented the same enhancement effect as p-benzoquinone due to generation of hypochlorous acid (HOCl) and more 1O2, which was completely different from the reported. This study develops a highly efficient green oxidation process and opens up a new insight in the remediation of contaminated water.