Effects of Dysprosium Oxide Nanoparticles on Escherichia coli

There is increasing interest in the study of dysprosium oxide nanoparticles (nDy2O3) for biomedical applications due to their fluorescence and paramagnetic properties. However, the fate of nDy2O3 and their effects on natural biological systems are a growing concern. This study assessed the toxicity of nDy2O3 on Escherichia coli for concentrations between 0.02 and 2 mg L−1, exposed to three concentrations of NaCl (8500, 850, and 85 mg L−1) and three glucose concentrations (35, 70, and 140 mg L−1). The ranges of these variables were selected to cover manufacturer recommendations of analytical methodologies for toxicity assessment, environmental and industrial nDy2O3 effluent concentrations, and metabolic activity. Two array-based toxicity techniques were used to evaluate the 27 combinations of conditions. Fluorescent dyes (Live/Dead) and respirometric assays were used to measure the undisturbed cell membrane (UCM) and remaining respiration percentage (RRP), respectively. Respirometric tests showed a higher toxic effect than Live/Dead test assays, indicating that metabolic processes are more affected than the physical structure of the cell by exposure to nDy2O3. After exposing the bacteria to concentrations of 2.0 mg L−1 uncoated nDy2O3 for 2 h at 85 mg L−1 NaCl and 140 mg L−1 glucose, the RRP and UCM decreased to 43% and 88%, respectively. Dysprosium ion (Dy+3) toxicity measurement suggested that Dy+3 was the main contributor to the overall toxicity

WTP for Water Filters and Water Quality Testing Services in Guatemala

We conduct a contingent valuation study to estimate the willingness to pay for a point-of-use water quality technology and water quality testing services in the highlands of Guatemala. This study is unique in two ways: we measure drinking water quality at the household level through water samples collected at the household and we elicit the willingness to pay for water quality testing services. We find a significant divergence in subjects’ perceptions of water quality and the measured bacteria counts in their household water. This divergence is economically important as perceptions may play a significant role in willingness to pay for water quality improvements

Aplicación de filtros cerámicos para la desinfección de aguas: análisis de variables en procesos de fabricación sobre la eficacia del tratamiento

En la actualidad más de 748 millones de personas carecen de acceso a agua potable en el mundo. Conseguir agua apta para el consumo es más difícil, y a menudo más caro, en las zonas rurales de los países en desarrollo. Por ello, una opción prometedora es la aplicación de filtros cerámicos para la desinfección de aguas. Se trata de filtros de sencillo diseño y bajo coste, fabricados en cerámica en forma de maceta, que alojan en torno a 10 litros de agua, suspendidos dentro de un receptáculo de plástico o cerámico, con un grifo y una tapa. Los usuarios vierten agua en el filtro, esperan a que ésta fluya a través del filtro hasta el receptáculo, y dispensan el agua accionando el grifo. Estos filtros se fabrican en más de 30 países, en fábricas diferentes y con tecnología diferente. En consecuencia, es objeto de este proyecto analizar la efectividad de varios filtros realizados con diferentes variables de fabricación sobre la desinfección de aguas para abastecimiento humano. Para ello se analizan muestras de filtros cerámicos producidos en 3 fábricas diferentes situadas en Indonesia, Tanzania y Nicaragua. Para determinar cómo afectan a la efectividad las diferentes arcillas de origen, material combustible (serrín o cáscara de arroz), y composición química del agua a los filtros recubiertos con nanopartículas de plata o nitrato de plata, se llevan a cabo los siguientes análisis: - Determinación de las características intrínsecas de los diferentes materiales. En base a los resultados de cálculo de coeficientes de advección y dispersión de los filtros se determina que los filtros fabricados con arcilla nicaragüense tienen los poros de mayor tamaño, y el soluto se propaga más rápidamente a través de ellos. Los tres tipos de filtros cerámicos tienen capacidad de eliminación bacteriana incluso sin aplicación de plata. - Pruebas microbiológicas con E. coli, determinando que la adición de especies de plata incrementa la eficacia de desactivación de los filtros. Se alcanza una eficiencia de desactivación similar en filtros con la misma concentración de diferentes especies de plata (plata coloidal o nitrato de plata) en filtros con el mismo tipo de arcilla, sin embargo, la desorción de plata es superior en filtros cubiertos con Ag+ que con nAg. - Evaluación de la influencia de la composición química del agua en el rendimiento de eliminación de bacterias de los filtros. Los resultados muestran que el efecto de la composición química del agua en la desinfección no es significante sobre otros parámetros como el tipo de arcilla o la concentración de plata aplicada a la matriz cerámica. - Determinación de la cantidad de bacterias viables en el interior de los poros de los filtros, donde una concentración más alta de plata muestra valores más bajos de bacterias en los filtros. - Análisis estadístico para comparar las medias de diferentes grupos y determinar si hay diferencias significativas entre los diferentes parámetros a analizar. No se observa una diferencia significativa en la eficacia de los filtros cerámicos hechos tanto con serrín como con cáscara de arroz como material combustible

Effect of Local Materials on the Silver Sorption and Strength of Ceramic Water Filters

In this paper, we present a systematic evaluation of the effects of local clays and the manufacturing process on the performance of ceramic water filters (CWFs) impregnated with silver compounds, which are used for point-of-use water treatment in developing countries. Mineral composition, silver sorption/desorption, and strength are the important characteristics that influence effectiveness and durability of CWFs during transport and use. Laboratory tests were conducted on ceramic samples obtained from five CWF factories around the world to determine their mineral composition, silver sorption/desorption, and flexural strength. The results of this study showed that clays that contain traces of crystalline albite or crystalline pyroxene have better sorption of silver species than those that do not. The results showed that the Freundlich model provided the best fit for both ionic silver and silver nanoparticles for all of the ceramic materials that were tested. Thus, this model can be used to optimize the manufacturing process and the application of silver. Silver nanoparticles were desorbed more slowly than ionic silver, so they last longer in the ceramic material. Water that contains a high concentration of divalent ions is not recommended for preparing solutions of silver nanoparticles due to aggregation of the particles, which limits their sorption by the ceramic materials. In this study, the mineralogy of the source materials was found to have the most significant influence on the strength of ceramic filters

Development of Ceramic Water Filter Clay Selection Criteria

Ceramic water filters (CWFs) are point-of-use drinking water treatment systems that are manufactured and used in under-served communities around the world. The clayey material (CM) used to manufacture CWFs is a locally sourced mixture of clay, sand, slit and amorphous material (usually dug near the CWF factory). CM varies in composition and purity depending on the geographical location and geological setting. In this study, a set of 13 CM samples collected from around the world were analyzed using grain size analysis, as well as liquid and plastic limit tests. Mineralogical composition was determined using X-ray diffraction. A selection of three CM samples (Guatemala, Canada, and Guinea Bissau) with a range of compositions were used to study biofilm growth on CM before and after firing. Biofilm coverage was studied on CM (before firing) and CWF material (after firing) using Pseudomonas fluorescens Migula. The average biofilm coverages for Guatemala, Canada, and Guinea Bissau CM were 20.03 ± 2.80%, 19.28 ± 0.91%, and 9.88 ± 4.02%, respectively. The average biofilm formation coverages for Guatemala, Canada, and Guinea Bissau CWF were 13.08 ± 1.74%, 10.36 ± 3.41%, and 8.66 ± 0.13%, respectively. The results presented here suggest that CM can be manipulated to manufacture better performing CWFs by engineering the soil characteristics, such as grain size, liquid and plastic limits, and mineralogy. This could improve the durability and biofilm resistance of CWFs

The Rhode Island Stormwater Management and Treatment Demonstration Facility

The occurrence of toxic heavy metals from Rhode Island highways, verified in a report completed by Thiem, Bade & Alkhatibe in 1998, showed that cadmium, chromium, copper, lead, nickel and zinc exceeded EPA’s acute and/or chronic water quality criteria. Besides toxic metals, stormwater also contains petroleum hydrocarbons, nutrients, and microbial matter as well as many other chemical compounds (Goebel et al., 2007). These toxic stormwater constituents are easily washed into water bodies, causing a decrease in overall stream diversity. The selection of the various, commercially available stormwater runoff commercial systems relies mostly on unverified manufacturer’s data or is based on performance reports from other parts of the country where local environmental conditions are much different than those in Rhode Island. The focus of this joint-research effort is to provide state agencies and the URI transportation community with a new facility where BMP structures can be evaluated against the manufacturer’s claims and under environmental conditions prevailing in our state. This facility will be known as the “Rhode Island Stormwater Management and Treatment Demonstration Facility” (RI SDF). Our research efforts can be groups in three major research taks. Task I revolves around the set-up of the RI SDF facility. Task II focuses the contaminant removal efficiencies of a commercial hydrodynamic separator unit, while the Task III seeks to evaluate the performance of pervious concrete amended with organo-soils. Task II and III will be the first projects to take advantage of the newly built RI SDF site

Synthesis of silver nanoparticles using a modified Tollens’ method in conjunction with phytochemicals and assessment of their antimicrobial activity

Background: Silver nanoparticles (AgNPs) have attracted great attention due to their outstanding electrical, optical, magnetic, catalytic, and antimicrobial properties. However, there is a need for alternative production methods that use less toxic precursors and reduce their undesirable by-products. Phyto-extracts from the leaves of olive and rosemary plants can be used as reducing agents and (in conjunction with Tollens’ reagent) can even enhance AgNP antimicrobial activity. Methods: Conditions for the proposed hybrid synthesis method were optimized for olive leaf extracts (OLEs) and rosemary leaf extracts (RLEs). The resultant AgNPs were characterized using UV–visible spectroscopy, an environmental scanning electron microscope, and Dynamic Light Scattering analysis. An atomic absorption spectrophotometer was used to measure AgNP concentration. Fourier transform infrared spectroscopy (FTIR) was used to determine the specific functional groups responsible for the reduction of both silver nitrate and capping agents in the leaf extract. Additionally, the antimicrobial properties of the synthesized AgNPs were assessed against Gram-negative bacteria (Escherichia coli and Salmonella enterica) and Gram-positive bacteria (Staphylococcus aureus), by using both the Kirby–Bauer and broth microdilution methods on Mueller–Hinton (MH) agar plates. Results and Discussion: A simple, feasible, and rapid method has been successfully developed for silver nanoparticle synthesis by reducing Tollens’ reagent using leaf extracts from olive and rosemary plants (widely available in Jordan). Scanning electron microscopy images showed that the method produces AgNPs with a spherical shape and average core sizes of 45 ± 2 and 38 ± 3 nm for OLE and RLE, respectively. A negative zeta potential (ζ) of −43.15 ± 3.65 mV for OLE-AgNPs and −33.65 ± 2.88mV for RLE-AgNPs proved the stability of silver nanoparticles. FTIR spectra for AgNPs and leaf extracts indicated that the compounds present in the leaf extracts play an important role in the coating/capping of synthesized nanoparticles. The manufactured AgNPs exhibited an antibacterial effect against Escherichia coli and Staphylococcus aureus with minimum inhibitory concentrations (MIC) of 9.38 and 4.69 μl/ml for OLE-AgNPs and RLE-AgNPs, respectively. The MIC for Salmonella enterica were 18.75 μl/ml for both OLE-AgNPs and RLE-AgNPs. Furthermore, our results indicated that the RLE-AgNPs exhibited a stronger antibacterial effect than OLE-AgNPs against different bacteria species. These results contribute to the body of knowledge on nanoparticle production using plant-mediated synthesis and performance. They also offer insights into the potential for scaling up this production process for commercial implementation

Prediction of the Limiting Flux and Its Correlation with the Reynolds Number during the Microfiltration of Skim Milk Using an Improved Model

Limiting flux (JL) determination is a critical issue for membrane processing. This work presents a modified exponential model for JL calculation, based on a previously published version. Our research focused on skim milk microfiltrations. The processing variables studied were the crossflow velocity (CFV), membrane hydraulic diameter (dh), temperature, and concentration factor, totaling 62 experimental runs. Results showed that, by adding a new parameter called minimum transmembrane pressure, the modified model not only improved the fit of the experimental data compared to the former version (R2 \u3e 97.00%), but also revealed the existence of a minimum transmembrane pressure required to obtain flux (J). This result is observed as a small shift to the right on J versus transmembrane pressure curves, and this shift increases with the flow velocity. This fact was reported in other investigations, but so far has gone uninvestigated. The JL predicted values were correlated with the Reynolds number (Re) for each dh tested. Results showed that for a same Re; JL increased as dh decreased; in a wide range of Re within the turbulent regime. Finally, from dimensionless correlations; a unique expression JL = f (Re, dh) was obtained; predicting satisfactorily JL (R2 = 84.11%) for the whole set of experiments

Removal of Escherichia coli and Faecal Coliforms from Surface Water and Groundwater by Household Water Treatment Devices/Systems: A Sustainable Solution for Improving Water Quality in Rural Communities of the Southern African Development Community Region

There is significant evidence that household water treatment devices/systems (HWTS) are capable of dramatically improving microbially contaminated water quality. The purpose of this study was to examine five filters [(biosand filter-standard (BSF-S); biosand filter-zeolite (BSF-Z); bucket filter (BF); ceramic candle filter (CCF); and silver-impregnated porous pot (SIPP)] and evaluate their ability to improve the quality of drinking water at the household level. These HWTS were manufactured in the workshop of the Tshwane University of Technology and evaluated for efficiency to remove turbidity, faecal coliforms and Escherichia coli from multiple water source samples, using standard methods. The flow rates ranged from 0.05 L/h to 2.49 L/h for SIPP, 1 L/h to 4 L/h for CCF, 0.81 L/h to 6.84 L/h for BSF-S, 1.74 L/h to 19.2 L/h and 106.5 L/h to 160.5 L/h for BF The turbidity of the raw water samples ranged between 2.17 and 40.4 NTU. The average turbidity obtained after filtration ranged from 0.6 to 8 NTU (BSF-S), 1 to 4 NTU (BSF-Z), 2 to 11 NTU (BF), and from 0.6 to 7 NTU (CCF) and 0.7 to 1 NTU for SIPP. The BSF-S, BSF-Z and CCF removed 2 to 4 log10 (99% to 100%) of coliform bacteria, while the BF removed 1 to 3 log (90% to 99.9%) of these bacteria. The performance of the SIPP in removing turbidity and indicator bacteria (>5 log10, 100%) was significantly higher compared to that of the other HWTS (p < 0.05). The findings of this study indicate that the SIPP can be an effective and sustainable HWTS for the Southern African Development Community (SADC) rural communities, as it removed the total concentration of bacteria from test water, can be manufactured using locally available materials, and is easy to operate and to maintain