Browsing by Author "Alvarez, Pedro"
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Item A Polysulfone/Cobalt Metal–Organic Framework Nanocomposite Membrane with Enhanced Water Permeability and Fouling Resistance(American Chemical Society, 2022) Gil, Eva; Huang, Xiaochuan; Zuo, Kuichang; Kim, Jun; Rincón, Susana; Rivera, José María; Ranjbari, Kiarash; Perreault, François; Alvarez, Pedro; Zepeda, Alejandro; Li, Qilin; Nanosystems Engineering Research Center for Nanotechnology Enabled Water TreatmentUltrafiltration membranes are widely used in water and wastewater applications. The two most important membrane characteristics that determine the cost-effectiveness of an ultrafiltration membrane process are membrane permeability and fouling resistance. Metal–organic frameworks (MOFs) have been intensively investigated as highly selective sorbents and superior (photo) catalysts. Their potential as membrane modifiers has also received attention recently. In this study, a non-functionalized, water-stable, nanocrystalline mixed ligand octahedral MOF containing carboxylate and amine groups with a cobalt metal center (MOF-Co) was incorporated into polysulfone (PSF) ultrafiltration (UF) membranes at a very low nominal concentration (2 and 4 wt %) using the conventional phase inversion method. The resultant PSF/MOF-Co_4% membrane exhibited water permeability up to 360% higher than of the control PSF membrane without sacrificing the selectivity of the membrane, which had not been previously achieved by an unmodified MOF. In addition, the PSF/MOF-Co_4% membrane showed strong resistance to fouling by natural organic matter (NOM), with 87 and 83% reduction in reversible and irreversible NOM fouling, respectively, compared to the control PSF membrane. This improvement was attributed to the increases in membrane porosity and surface hydrophilicity resulting from the high hydrophilicity of the MOF-Co. The capability of increasing membrane water permeability and fouling resistance without compromising membrane selectivity makes the MOF-Co and potentially other hydrophilic MOFs excellent candidates as membrane additives.Item Embargo Antibiotic resistance: Overlooked ARG reservoirs, dissemination pathways, and a novel control strategy(2022-08-05) Sun, Ruonan; Alvarez, PedroThe global spread of antibiotic resistance genes (ARGs) has resulted in significant societal and economic costs of treating antibiotic-resistant bacterial infections. Even countries that have made substantial efforts to decrease the misuse and overuse of antibiotics still experience increasing rates of clinical antibiotic resistance, emphasizing the complexity of this problem. This dissertation contributes to improving the understanding of overlooked ARG sources and dissemination pathways, as well as the development of ARG control strategies to enhance the mitigation of the associated risks. Wildlife carrying resistome, especially wild birds, could be an important but overlooked ARG reservoir and dissemination vector, and urbanization could amplify such risks as it fosters many overlapping habitats and frequent interactions between wildlife populations and human communities. We analyzed fresh feces from three common bird species living in urban environments (Houston metropolitan areas). ARGs encoding resistance to three major classes of antibiotics (i.e., tetracyclines, β-lactams, and sulfonamides) and the mobile genetic element integrase gene (intI1) were abundant (up to 1e+10 copies/g dry feces), with relative concentrations surprisingly comparable to that in poultry and livestock that are occasionally fed with antibiotics. Biomarkers for opportunistic pathogens were also abundant (up to 1e+7 copies/g dry feces) and the dominant isolates (i.e., Enterococcus spp. and Pseudomonas aeruginosa) harbored both ARGs and virulence genes. ARGs and intI1 in these bird feces exhibited moderate persistence and increased the local resistome in the receiving soil, indicating an enlarged region of influence beyond the bird feces. Horizontal gene transfer (HGT) greatly prompts the dissemination of antibiotic resistance into pathogens, and conjugation is often considered to be the major HGT pathway. The contribution of phage-mediated transduction (relative to via conjugation) in various environmental settings remains poorly understood, despite the abundance of phage-borne ARGs. We investigated the influence of bacterial concentration and water turbulence level (quantified as Reynold’s number (Re)) in suspended growth systems on the frequency of ARG transfer by two mechanisms: delivery by a lysogenic phage λ and conjugation mediated by a self-transmissible plasmid RP4. Using Escherichia coli as recipient, phage delivery had a comparable frequency to that of conjugation in suspensions with low bacterial concentration (1e+4 CFU/mL) and moderate turbulence (Re = 5e+4). At 1e+7 CFU/mL, no significant difference was observed between the frequencies of ARG transfer by the two mechanisms under quiescent water conditions or when Re reached 5e+5, corroborating the simulation of cell- (or phage)-to-cell collisions. The frequency of ARG dissemination via phage delivery might be further enhanced due to the co-occurrence with aged microplastics, which can act as sinks of common chemical contaminants (e.g., antibiotics) and microbes. Here, we used UV-aged polystyrene microplastics (PS-MPs) to investigate how microplastic aging affects phage delivering ARGs. Relative to pristine PS-MPs (MP0), the adsorption capacity of MP20 (20-day UV-aged PS-MPs) towards phage λ and recipient cell E. coli increased by 8.3- and 6.6-fold, respectively. Moreover, MP20 released more organic compounds (possibly depolymerization byproducts) that upregulated phage infection associated genes. Accordingly, MP20 enhanced the frequency of phage-mediated ARG transfer by 3.5-fold. Lysogenic phage might facilitate ARG dissemination, while polyvalent lytic phage can be harnessed for efficient killing of antibiotic resistant pathogens. Biofilms pervasive in drinking water systems can harbor resistant pathogens and thus raise great health concerns. Here, we explored the use of peptide display on engineered filamentous coliphage M13 for precise delivery of polyvalent lytic phages to control resistant pathogens in biofilms. M13 phage was dual-modified to display biofilm-binding peptides (presenting high affinity to P. aeruginosa polysaccharides) on major coat protein (pVIII) and peptides specific for polyvalent lytic phage on tail fiber protein (pIII). The modified M13 had 5-fold higher affinity for P. aeruginosa-dominated mixed-species biofilms than unconjugated polyvalent lytic phage. When applied to a simulated water distribution system, the resulting phage conjugates achieved targeted phage delivery to the biofilms and were more effective than polyvalent lytic phages alone in reducing live bacterial biomass (84% vs 34%). Biofilm regrowth was also mitigated as phage conjugates further downregulated bacterial genes associated with biofilm formation. Overall, these findings characterize some overlooked ARG reservoirs and dissemination vectors that require mitigations. Wild birds are important carriers of ARGs in urban areas. The contribution of phages to ARG horizontal transfer is sometimes comparable to that of conjugation, and it can be considerably enhanced in the presence of aged microplastics. Phages can also target resistant pathogens harbored in biofilms, and their delivery could be enhanced by peptide display strategies that enable biofilm eradication in drinking water storage and distribution systems.Item Characterization of Friction Reducer Properties in Oil-Field Operations(2015-01-15) Bolanos Ellis, Valerie; Tomson, Mason B.; Alvarez, Pedro; Bedient, Philip; Tomson , RossFriction reducers are essential additives used to economically achieve the high pumping rates required for slickwater fracturing. Decreased friction reducer performance in high-TDS brines has been a major challenge for reusing produced water in hydraulic fracturing. Little work has been done to identify the specific parameters that affect polymeric friction reduction. This research uses friction flow loop experiments to characterize the performance of partially hydrolyzed polyacrylamide friction reducers in conditions relevant to the oil field. Polymer concentration and degree of hydrolysis effects on friction reduction are evaluated in the ranges of 0.25-2 gpt and 0-30%, respectively. The decrease in friction reducer performance is measured in brines up to 120,000 mg/L TDS with varying multivalent cation concentrations. The friction reducer interactions with Na+, Ca2+, Mg2+, Fe3+, and Al 3+ ions are individually assessed. The results are compared to experiments with a commercial friction reducer, and used to propose an empirical model to predict friction reducer performance based on water composition.Item Embargo Enhancing Membrane Distillation Performance Using Carbon Nanomaterials(2021-11-22) Xin, Ruikun; Li, Qilin; Alvarez, Pedro; Lou, Jun; Getachew , BezawitMembrane distillation (MD) is a promising technology to treat high salinity wastewater, but the high operational cost, lack of comprehensive understanding in its heat and mass transfer, and limited ability in treating various wastewater (e.g., low surface tension wastewater, volatile contaminants rich wastewater, etc.) have impeded its translation from bench scale to field scale. Nanophotonic-Enabled Solar Membrane Distillation (NESMD) utilizes free sunlight to produce localized heat on the membrane surface, which can make MD economically viable. However, the current membranes for NESMD exhibit either an increased mass transfer resistance to water vapor or a decreased photothermal properties after immobilized on the substrate membrane surface. Plus, unlike conventional MD whose performance dependency on the operational and environmental conditions are well understood, the operational and environmental effects on NESMD have not been fully understood. In addition, none of the existing NESMD membrane is anti-wetting, which limits its application only in dealing high surface tension wastewaters. Lastly, all current MD and NESMD membranes suffer from the problem of poor rejection against volatile contaminants (VC). In this dissertation, core-shell structure hydrophilic photothermal nanofiber is used to solve the tradeoff between membrane permeability and solar absorptivity. With good water stability, high solar absorbance, fast heating and heat dissipation abilities, and no additional vapor mass transfer resistance, it can be used as a coating material to convert a commercial membrane to a photothermal active membrane. Compared to existing solar MD coating materials, the novel core-shell structure coating shows a better solar MD performance. To understand the impact of operation and environmental factors on NESMD, the response of NESMD to the environmental (i.e., solar irradiance, and feed water temperature and salinity) and operating conditions (e.g., feed flowrate) were systematically investigated. The results show that NESMD perform better under higher solar irradiance and feed/permeate inlet temperature, and lower IR portion light source, feed salinity, and feed flowrate. To enable NESMD in treating low surface tension wastewater, a dual functional, omniphobic−photothermal nanocomposite membrane was developed to achieve wetting resistance and low energy consumption. The membrane was prepared by forming a hierarchical structure of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS17) modified carbon black (CB) nanoparticles (NPs) on a polyvinylidene fluoride (PVDF) membrane surface. The fluorinated CB NPs absorbed sun light to provide localized heating for NESMD, which increased membrane flux by 25% upon simulated solar irradiation at one sun unit. The utilization efficiency of solar energy in the NESMD process, 75.9%, is more than one order of magnitude higher than the energy efficiency of the conventional direct contact membrane distillation process. Furthermore, the re-entrant structure formed by the CB NPs together with the hydrophobic FAS17 coating led to low surface energy and hence omniphobicity, increasing the contact angle of the 80 vol% ethanol-in-water from 0 to 94.2°. As a result, the dual functional membrane exhibited much higher resistance to wetting by surfactants. Whereas the pristine PVDF membrane was wetted by 0.2 mM SDS, SDS had no effect on the dual function membrane over the whole SDS concentration range tested (0.1 – 0.4 mM). The photothermal activity, improved thermal efficiency, and strong wetting resistance make the dual functional omniphobic−photothermal membrane an excellent membrane material for the NESMD process. Lastly, to improve the VC rejection ability in MD, Graphene oxide (GO) based membranes were fabricated by sandwiching GO and ethylene diamine crosslinked GO (GO-EDA) between a commercial polyvinylidene difluoride (PVDF) membrane and electrospun PVDF nanofiber, and tested their volatile contaminant rejection under different feed temperature, feed pH, and durations by using NH3 as a model volatile contaminant. For the first time, a volatile-contaminants-rejective MD membrane was reported, and the rejection mechanism of NH3 by GO membrane was revealed. Compared to commercial MD membrane, under different experimental conditions, our GO-based membranes always show two orders of magnitude better NH3 rejection with only one third drop in water vapor mass transfer resistance. The NH3 rejection of GO membrane is as high as 97.8%, which is 2.7 times better than the state of art RO membrane. The high volatile contaminants rejection makes our GO membrane good candidates in treating volatile contaminants rich wastewater.Item Unknown High Concentration Organic Wastewater with High Phosphorus Treatment by Facultative MBR(MDPI, 2021) Wang, Bing; Liu, Yunlong; Zhang, Siyu; Zhang, Kaihang; Alvarez, Pedro; Crittenden, John C.; Sun, Bing; Yang, Lin; Liu, Su; Ran, ZhilinPhosphorus is one of the main factors causing water eutrophication, and the traditional phosphorus removal process causes phosphorus-rich sludge pollution. The facultative MBR process uses phosphate-reducing bacteria to convert phosphate into directly recyclable gaseous phosphine to solve this malpractice and make sewage become a new phosphorus resource. In order to investigate the phosphorus removal efficiency and the mechanism under facultative conditions, run the facultative MBR reactor for 30 days. The COD value, phosphate concentration, and phosphine yield were measured, and the changes of sludge metabolic pathway abundance and community composition in different periods were detected. According to the measurement, the maximum phosphorus removal efficiency is 43.11% and the maximum yield of phosphine is 320 μg/m3 (measured by the volume of sewage). Combined with thermodynamic analysis, the microbial mechanism of the reactor was proposed, and the possible transformation pathway of phosphorus was analyzed. At last, changes the phosphorus removal process from the ‘removal type’ to the ‘recycling type’.Item Unknown Microbial Fuel Cells under Extreme Salinity(2016-04-20) Monzon del Olmo, Oihane; Alvarez, PedroI developed a Microbial Fuel Cell (MFC) that unprecedentedly works (i.e., produces electricity) under extreme salinity (≈ 100 g/L NaCl). Many industries, such as oil and gas extraction, generate hypersaline wastewaters with high organic strength, accounting for about 5% of worldwide generated effluents, which represent a major challenge for pollution control and resource recovery. This study assesses the potential for microbial fuel cells (MFCs) to treat such wastewaters and generate electricity under extreme saline conditions. Specifically, the focus is on the feasibility to treat hypersaline wastewater generated by the emerging unconventional oil and gas industry (hydraulic fracturing) and so, with mean salinity of 100 g/L NaCl (3-fold higher than sea water). The success of this novel technology strongly depends on finding a competent and resilient microbial community that can degrade the waste under extreme saline conditions and be able to use the anode as their terminal electron acceptor (exoelectrogenic capability). I demonstrated that MFCs can produce electricity at extremely high salinity (up to 250 g/l NaCl) with a power production of 71mW/m2. Pyrosequencing analysis of the anode population showed the predominance of Halanaerobium spp. (85%), which has been found in shale formations and oil reservoirs. Promoting Quorum sensing (QS, cell to cell communication between bacteria to control gene expression) was used as strategy to increase the attachment of bacteria to the anode and thus improve the MFC performance. Results show that the power output can be bolstered by adding 100nM of quinolone signal with an increase in power density of 30%, for the first time showing QS in Halanaerobium extremophiles. To make this technology closer to market applications, experiments with real wastewaters were also carried out. A sample of produced wastewater from Barnet Shale, Texas (86 g/L NaCl) produced electricity when fed in an MFC, leading to my discovery of another predominant electroactive and halophile specie in the anode, Marinobacter hydrocarbonoclasticus, which is known for its extraordinary biodegradation capabilities. These findings suggest the potential of the MFC technology to treat hypersaline high-strength wastewaters while producing electricity, a result which would alleviate a major economic and environmental challenge for the oil and gas industry. In addition, this research represents a promising start overall in advancing biological treatment of saline wastewaters in other contexts, which is a largely unexploited field.Item Unknown Surface Imprinted Particles for the Removal of Coronaviruses from Aqueous Solution(2023-01-30) Senehi, Naomi; Alvarez, Pedro; Stadler, LaurenCoronaviruses are responsible for the deadly COVID-19 pandemic and are the second most common cause of the common cold. Efforts to monitor coronaviruses in wastewater treatment systems have skyrocketed, however, current analytical methods to quantify coronavirus virions require a combination of selective assays (e.g., RT-qPCR) and infectious assays (e.g., TCID50). When combined with devices such as sensors, molecular imprinting is a promising strategy to obtain a direct measure of specific infectious viruses. However, effective imprinting templates are yet to be elucidated. We designed and fabricated glycoprotein imprinted particles (GIPs). GIPs were found to selectively remove two types of coronaviruses (HCoV-OC43 and HCoV-NL63) efficiently from solution with greater than 1-log (90%) removal in under ten minutes. Selective adsorption was maximized at pH 6, the glycoprotein isoelectric point, which highlights the role of electrostatic interactions on separation efficiency and was confirmed using protein modeling. At pH 6, during competitive adsorption, the GIPs adsorbed more of the target virions (HCoV-OC43) than non-target virions (HCoV-NL63) which further promotes the use of glycoprotein templates for effective imprinted particles. Overall, these results highlight the benefits of GIPs and pave the way for imprinting techniques for the separation of other viruses.Item Unknown Thermal Remediation: Enhancing Ecosystem Recovery for Soils Contaminated with Heavy Hydrocarbons(2017-11-30) Vidonish, Julia Elizabeth; Alvarez, Pedro; Zygourakis, KyriacosTerrestrial spills of crude oil and refined petroleum products have substantial environmental, economic, and public health consequences. Thermal treatment technologies hold an important niche in the remediation of hydrocarbon-contaminated soils and sediments due to their ability to quickly and reliably meet cleanup standards. However, sustained high temperature can be energy intensive and can damage soil properties. Pyrolysis of hydrocarbon-contaminated soils offers the potential for rapid remediation with fewer effects on soil fertility than existing thermal technologies. Pyrolysis of contaminated soils at 420ºC converted recalcitrant heavy hydrocarbons into “char” (a carbonaceous material like petroleum coke) and enhanced soil fertility. Pyrolytic treatment reduced total petroleum hydrocarbons (TPH) to below regulatory standards (typically < 1% by weight) within 3 h using only 40-60% of the energy required for incineration at 600-1200ºC. Formation of polycyclic aromatic hydrocarbons (PAHs) was not observed, with post-pyrolysis levels well below applicable standards. Plant growth studies showed higher biomass production of Arabidopsis thaliana and Lactuca sativa (Simpson black-seeded lettuce) (80-900% heavier) in pyrolyzed soils than in contaminated or incinerated soils. Elemental analysis showed that pyrolyzed soils contained more carbon than incinerated soils (1.4-3.2% versus 0.3-0.4%). Using thermogravimetry and evolved gas analysis, we identified the two stages of pyrolytic remediation. Desorption of light hydrocarbons is the dominant process for temperatures between 150 and 350oC. Pyrolysis reactions dominate in the 400-500oC range releasing gaseous products (hydrogen, methane, higher alkanes and olefins) and forming a solid char. XPS analysis and partial combustion revealed that the char forms a layer coating the particles of treated soils. Since pyrolysis can effectively reduce the TPH of contaminated soils at temperatures below 500oC, it avoids carbonate decomposition reactions that may lead to large soil pH increases and severe loss of fertility. This is a significant potential advantage over competing thermal processes that expose contaminated soil to temperatures above 500oC. Overall, the convergence of treatment process engineering with soil science, ecosystem ecology, and plant biology research is essential to fill critical knowledge gaps and improve both the removal efficiency and sustainability of thermal technologies.Item Unknown Titanium oxide improves boron nitride photocatalytic degradation of perfluorooctanoic acid(Elsevier, 2022) Duan, Lijie; Wang, Bo; Heck, Kimberly N.; Clark, Chelsea A.; Wei, Jinshan; Wang, Minghao; Metz, Jordin; Wu, Gang; Tsai, Ah-Lim; Guo, Sujin; Arredondo, Jacob; Mohite, Aditya D.; Senftle, Thomas P.; Westerhoff, Paul; Alvarez, Pedro; Wen, Xianghua; Song, Yonghui; Wong, Michael S.; Center for Nanotechnology Enabled Water TreatmentBoron nitride (BN) has the newly-found property of degrading recalcitrant polyfluoroalkyl substances (PFAS) under ultraviolet C (UV-C, 254 nm) irradiation. It is ineffective at longer wavelengths, though. In this study, we report the simple calcination of BN and UV-A active titanium oxide (TiO2) creates a BN/TiO2 composite that is more photocatalytically active than BN or TiO2 under UV-A for perfluorooctanoic acid (PFOA). Under UV-A, BN/TiO2 degraded PFOA ∼ 15 × faster than TiO2, while BN was inactive. Band diagram analysis and photocurrent response measurements indicated that BN/TiO2 is a type-II heterojunction semiconductor, facilitating charge carrier separation. Additional experiments confirmed the importance of photogenerated holes for degrading PFOA. Outdoor experimentation under natural sunlight found BN/TiO2 to degrade PFOA in deionized water and salt-containing water with a half-life of 1.7 h and 4.5 h, respectively. These identified photocatalytic properties of BN/TiO2 highlight the potential for the light-driven destruction of other PFAS.