Showing papers by "Pedro J. J. Alvarez published in 2020"

2D N-Doped Porous Carbon Derived from Polydopamine-Coated Graphitic Carbon Nitride for Efficient Nonradical Activation of Peroxymonosulfate

Abstract: Nitrogen-doped carbon materials attract broad interest as catalysts for peroxymonosulfate (PMS) activation toward an efficient, nonradical advanced oxidation process. However, synthesis of N-rich carbocatalysts is challenging because of the thermal instability of desirable nitrogenous species (pyrrolic, pyridinic, and graphitic N). Furthermore, the relative importance of different nitrogenous configurations (and associated activation mechanisms) are unclear. Herein, we report a "coating-pyrolysis" method to synthesize porous 2D N-rich nanocarbon materials (PCN-x) derived from dopamine and g-C3N4 in different weight proportions. PCN-0.5 calcined at 800 °C had the highest surface area (759 m2/g) and unprecedentedly high N content (18.5 at%), and displayed the highest efficiency for 4-chlorophenol (4-CP) degradation via PMS activation. A positive correlation was observed between 4-CP oxidation rates and the total pyridinic and pyrrolic N content. These N dopants serve as Lewis basic sites to facilitate 4-CP adsorption on the PCN surface and subsequent electron-transfer from 4-CP to PMS, mediated by surface-bound complexes (PMS-PCN-0.5). The main degradation products were chlorinated oligomers (mostly dimeric biphenolic compounds), which adsorbed to and deteriorated the carbocatalyst. Overall, this study offers new insights for rational design of nitrogen-enriched carbocatalysts, and advances mechanistic understanding of the critical role of N species during nonradical PMS activation.

Antibiotic resistance genes from livestock waste: occurrence, dissemination, and treatment

Abstract: Antibiotics are widely used in animal husbandry, and various types of antibiotic resistance genes (ARGs) are frequently detected in livestock waste around the world. Conventional livestock waste treatment processes do not completely remove ARGs, resulting in their release to soil and water environments. Various exposure routes of these ARGs to humans, including inhalation and ingestion of antibiotic-resistant bacteria (ARB) that harbor them, may be contributing to the rise in resistant clinical infections that are increasingly difficult to treat with antibiotics. In this review, we assess the occurrence and variability of ARGs in livestock wastes and their potential propagation pathways to human pathogens. We also review the mechanisms and environmental factors that influence the dissemination of ARGs through these pathways, and evaluate the ARG removal efficiency of common livestock waste management approaches. Challenges and research needs for assessing and mitigating the risk of antibiotic resistance dissemination from livestock waste are also presented.

Rethinking wastewater risks and monitoring in light of the COVID-19 pandemic

Abstract: The COVID-19 pandemic has severely impacted public health and the worldwide economy Converging evidence from the current pandemic, previous outbreaks and controlled experiments indicates that SARS-CoVs are present in wastewater for several days, leading to potential health risks via waterborne and aerosolized wastewater pathways Conventional wastewater treatment provides only partial removal of SARS-CoVs, thus safe disposal or reuse will depend on the efficacy of final disinfection This underscores the need for a risk assessment and management framework tailored to SARS-CoV-2 transmission via wastewater, including new tools for environmental surveillance, ensuring adequate disinfection as a component of overall COVID-19 pandemic containment Converging evidence indicates that SARS-CoVs are present in wastewater for several days with potential health risks This Review analyses knowledge about such risks as well as the potential spread of SARS-CoVs in waterborne, waterborne–aerosolized and waterborne–foodborne pathways during a pandemic

Opportunities for nanotechnology to enhance electrochemical treatment of pollutants in potable water and industrial wastewater – a perspective

Abstract: Based upon an international workshop, this perspective evaluates how nano-scale pore structures and unique properties that emerge at nano- and sub-nano-size domains could improve the energy efficiency and selectivity of electroseparation or electrocatalytic processes for treating potable or waste waters An Eisenhower matrix prioritizes the urgency or impact of addressing potential barriers or opportunities There has been little optimization of electrochemical reactors to increase mass transport rates of pollutants to, from, and within electrode surfaces, which become important as nano-porous structures are engineered into electrodes A “trap-and-zap” strategy is discussed wherein nanostructures (pores, sieves, and crystal facets) are employed to allow localized concentration of target pollutants relative to background solutes (ie, localized pollutant trapping) The trapping is followed by localized production of tailored reactive oxygen species to selectively degrade the target pollutant (ie, localized zapping) Frequently overlooked in much of the electrode-material development literature, nano-scale structures touted to be highly “reactive” towards target pollutants may also be the most susceptible to material degradation (ie, aging) or fouling by mineral scales that form due to localized pH changes A need exists to study localized pH and electric-field related aging or fouling mechanisms and strategies to limit or reverse adverse outcomes from aging or fouling This perspective provides examples of the trends and identifies promising directions to advance nano-materials and engineering principles to exploit the growing need for near chemical-free, advanced oxidation/reduction or separation processes enabled through electrochemistry

Selective Adsorption and Photocatalytic Degradation of Extracellular Antibiotic Resistance Genes by Molecularly-Imprinted Graphitic Carbon Nitride.

Abstract: There is a growing need to mitigate the discharge of extracellular antibiotic resistance genes (ARGs) from municipal wastewater treatment systems. Here, molecularly-imprinted graphitic carbon nitride (MIP-C3N4) nanosheets were synthesized for selective photocatalytic degradation of a plasmid-encoded ARG (blaNDM-1, coding for multidrug resistance New Delhi metallo-β-lactamase-1) in secondary effluent. Molecular imprinting with guanine enhanced ARG adsorption, which improved the utilization of photogenerated oxidizing species to degrade blaNDM-1 rather than being scavenged by background nontarget constituents. Consequently, photocatalytic removal of blaNDM-1 in secondary effluent with MIP-C3N4 (k = 0.111 ± 0.028 min-1) was 37 times faster than with bare graphitic carbon nitride (k = 0.003 ± 0.001 min-1) under UVA irradiation (365 nm, 3.64 × 10-6 Einstein/L·s). MIP-C3N4 can efficiently catalyze the fragmentation of blaNDM-1, which decreased the potential for ARG repair by transformed bacteria. Molecular imprinting also changed the primary degradation pathway; electron holes (h+) were the predominant oxidizing species responsible for blaNDM-1 removal with MIP-C3N4 versus free radicals (i.e., ·OH and O2-) for coated but nonimprinted C3N4. Overall, MIP-C3N4 efficiently removed blaNDM-1 from secondary effluent, demonstrating the potential for molecular imprinting to enhance the selectivity and efficacy of photocatalytic processes to mitigate dissemination of antibiotic resistance from sewage treatment systems.

The importance of system configuration for distributed direct potable water reuse

Abstract: Water and wastewater infrastructure worldwide faces unprecedented demand and supply conflicts that require unconventional solutions. In this study, we develop a novel modelling framework to assess the environmental and economic implications of a hybrid water supply system that supplements a centralized surface water supply with distributed direct potable reuse (DPR) of municipal wastewater, as a strategy to address such challenges. The model is tested with real water and wastewater systems data from the City of Houston, Texas. Results show that supplementing the conventional centralized water supply with distributed DPR would reduce water age in the drinking-water distribution network and hence improve water quality; properly designed system configurations attain system-wide net energy savings even with the high energy consumption of existing technologies used for advanced treatment of the wastewater. A target energy efficiency for future advanced treatment technologies is identified to achieve net energy saving with all hybrid system configurations. Furthermore, distributed DPR remains financially competitive compared with other unconventional water supply solutions. The modelling framework and associated databases developed in this study serve an important research need for quantitatively characterizing distributed and hybrid water systems, laying the necessary foundation for rational design of integrated urban water systems. Water and wastewater infrastructure worldwide faces unprecedented challenges. A new model can assess the environmental and economic implications of a hybrid water supply system that provides a centralized surface water supply with distributed direct potable reuse of municipal wastewater.

Role of Extracellular Polymeric Substances in Microbial Reduction of Arsenate to Arsenite by Escherichia coli and Bacillus subtilis

Abstract: We show that arsenate can be readily reduced to arsenite on cell surfaces of common bacteria (E. coli or B. subtilis) or in aqueous dissolved extracellular polymeric substances (EPS) extracted from...

Nanocrystal facet modulation to enhance transferrin binding and cellular delivery.

Abstract: Binding of biomolecules to crystal surfaces is critical for effective biological applications of crystalline nanomaterials. Here, we present the modulation of exposed crystal facets as a feasible approach to enhance specific nanocrystal-biomolecule associations for improving cellular targeting and nanomaterial uptake. We demonstrate that facet-engineering significantly enhances transferrin binding to cadmium chalcogenide nanocrystals and their subsequent delivery into cancer cells, mediated by transferrin receptors, in a complex biological matrix. Competitive adsorption experiments coupled with theoretical calculations reveal that the (100) facet of cadmoselite and (002) facet of greenockite preferentially bind with transferrin via inner-sphere thiol complexation. Molecular dynamics simulation infers that facet-dependent transferrin binding is also induced by the differential affinity of crystal facets to water molecules in the first solvation shell, which affects access to exposed facets. Overall, this research underlines the promise of facet engineering to improve the efficacy of crystalline nanomaterials in biological applications.

Discerning the Relevance of Superoxide in PFOA Degradation

Abstract: Perfluorooctanoic acid (PFOA) is a widely distributed recalcitrant contaminant. In recent years, advanced oxidation processes have been explored for PFOA degradation, yet factors influencing their ...

Hormetic Promotion of Biofilm Growth by Polyvalent Bacteriophages at Low Concentrations.

Abstract: Interactions between bacteriophages (phages) and biofilms are poorly understood despite their broad ecological and water quality implications. Here, we report that biofilm exposure to lytic polyvalent phages at low concentrations (i.e., 102-104 phages/mL) can counterintuitively promote biofilm growth and densification (corroborated by confocal laser scanning microscopy (CLSM)). Such exposure hormetically upregulated quorum sensing genes (by 4.1- to 24.9-fold), polysaccharide production genes (by 3.7- to 9.3-fold), and curli synthesis genes (by 4.5- to 6.5-fold) in the biofilm-dwelling bacterial hosts (i.e., Escherichia coli and Pseudomonas aeruginosa) relative to unexposed controls. Accordingly, the biofilm matrix increased its polysaccharide and extracellular DNA content relative to unexposed controls (by 41.8 ± 2.3 and 81.4 ± 2.2%, respectively), which decreased biofilm permeability and increased structural integrity. This contributed to enhanced resistance to disinfection with chlorine (bacteria half-lives were 6.08 ± 0.05 vs 3.91 ± 0.03 min for unexposed controls) and to subsequent phage infection (biomass removal was 18.2 ± 1.2 vs 32.3 ± 1.2% for unexposed controls), apparently by mitigating diffusion of these antibacterial agents through the biofilm. Overall, low concentrations of phages reaching a biofilm may result in unintended biofilm stimulation, which might accelerate biofouling, biocorrosion, or other biofilm-related water quality problems.

Ammonium Enhances Food Waste Fermentation to High-Value Optically Active l-Lactic acid

Abstract: Fermentation of food waste to l-lactic acid (l-LA), a high value-added platform molecule, is a green approach for resource recovery. However, low yield and optical activity (OA) of l-LA are key lim...

Ionic Liquid Enriches the Antibiotic Resistome, Especially Efflux Pump Genes, Before Significantly Affecting Microbial Community Structure

Abstract: An expanding list of chemicals may permeabilize bacterial cells and facilitate horizontal gene transfer (HGT), which enhances propagation of antibiotic resistance genes (ARGs) in the environment. Previous studies showed that 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]), an ionic liquid, can facilitate HGT of some ARGs among bacteria. However, the dynamic response of a wider range of ARGs and associated mobile genetic elements (MGEs) in different environments is unknown. Here, we used metagenomic tools to study shifts of the resistome and microbiome in both sediments and freshwater microcosms exposed to [BMIm][PF6]. Exposure for 16 h to 0.1 or 1.0 g/L significantly enriched more than 207 ARG subtypes primarily encoding efflux pumps in freshwater microcosms as well as cultivable antibiotic-resistant bacteria. This resistome enrichment was attributed to HGT facilitated by MGEs (428 plasmids, 61 integron-integrase genes, and 45 gene cassettes were enriched) as well as to HGT-related functional genes. Interestingly, resistome enrichment occurred fast (within 16 h) after [BMIm][PF6] exposure, before any significant changes in bacterial community structure. Similar ARG enrichment occurred in sediment microcosms exposed to [BMIm][PF6] for 28 d, and this longer exposure affected the microbial community structure (e.g., Proteobacteria abundance increased significantly). Overall, this study suggests that [BMIm][PF6] releases could rapidly enrich the antibiotic resistome in receiving environments by increasing HGT and fortuitously selecting for efflux pump genes, thus contributing to ARG propagation.

Treatment of aqueous solutions of 1,4-dioxane by ozonation and catalytic ozonation with copper oxide (CuO).

Abstract: In this study, treatment for the removal of 1,4-dioxane by ozone and by catalytic ozonation using CuO as the catalyst was investigated. While the removal of 1,4-dioxane was small (20%) and minerali...

Enhanced long-term attenuation of 1,4-dioxane in bioaugmented flow-through aquifer columns.

Abstract: Long term natural attenuation of 1,4-dioxane (dioxane) and its enhanced biodegradation after bioaugmentation with Pseudonocardia dioxanivorans CB1190 were assessed using flow-through aquifer columns. Natural attenuation of dioxane was not observed even after 2 years of acclimation. However, dioxane removal was observed in the bioaugmented columns (34% when the influent was 200 µg/L and 92% for 5 mg/L). The thmA gene that encodes the tetrahydrofuran monooxygenase that initiates dioxane degradation by CB1190 was only detected at the inoculation port and persisted for months after inoculation, implying the resiliency of bioaugmentation and its potential to offer long-term enhanced biodegradation capabilities. However, due to extensive clumping and limited mobility of CB1190, the augmented catabolic potential may be restricted to the immediate vicinity of the inoculation port. Accordingly, bioaugmentation with CB1190 seems more appropriate for the establishment of biobarriers. Bioaugmentation efficiency was associated with the availability of oxygen. Aeration of the column influent to increase dissolved oxygen significantly improved dioxane removal (p < 0.05), suggesting that (for sites with oxygen-limiting conditions) bioaugmentation can benefit from engineered approaches for delivering additional oxygen.

Beta-lactam-Induced Outer Membrane Alteration Confers E. coli a Fortuitous Competitive Advantage through Cross-Resistance to Bacteriophages

Abstract: Bacteriophages play an important role in controlling bacteria populations; yet, little is known about their differential effects on antibiotic resistant bacteria (ARB) proliferation. Here, we repor...

Engineering of CoSe2 Nanosheets via Vacancy Manipulation for Efficient Cancer Therapy

Abstract: CoSe2 nanosheets with different vacancy associates (i.e., VSeSe, VCoCoSe, VCoSeSe, and VCoCoCoSe) were synthesized by selecting different templates and calcination temperatures. The nanosheets havi...

Kinetic modeling of deep vacuum residue hydroconversion in a pilot scale continuous slurry reactor with recycle

Abstract: Slurry phase hydroconversion is a developing technology with the potential to completely upgrade Vacuum Residues (VR). In this work we use data from a continuous pilot plant with recycle to test and extend an existing distributed lumped kinetic model. The new data includes results from 134 steady state experiments with a Heavy Iran VR, including some at very high conversion, and allows sediment production rates to be quantified as well as sulphur removal in the form of H2S. The purpose of the work is to study the impact of the deep conversion reaction conditions and feedstock on the reaction kinetics. The model uses nineteen distributed lumps to represent the heavy hydrocarbons undergoing hydroconversion and hydrodesulphurisation with VR defined as the boiling range > 525°C. Reaction rates are based on molar concentrations. Hydrogen consumption and sediment production are taken into account in the model, as well as vapour liquid mass transfer resistances and vapour-liquid equilibrium. Parameter estimation has been carried out and the model provides a good fit with the experimental data. The modelling exercise found that, at very high conversions, thermal reactions give way to a cascade of catalytic reactions. The model gave a moderate fit for hydrogen consumption rates, which are strongly dependent on feedstock. Accumulation of sediment at high conversions was identified and well represented and the description of hydrodesulfurisation rates as proportional to cracking rates was validated.