Microbial Particle Research Articles

Tailored biolixiviation of spent LiCoO2 cathode batteries for sustainable metal recovery: Effects of consortia adaptation and particle size

With the rise of lithium-ion battery production, recycling valuable metals like Fe, Al, Cu, Ni, and Co is crucial. This study explores sustainable recovery from spent LiCoO2 cathode batteries via biolixiviation, focusing on microbial adaptation and particle size. Batteries were shredded into four size fractions, with mid-sized fractions (0.5–6 mm) showing the highest metal content and optimal microbial conditions. Microbial consortia were isolated using Modified Czapek-Dox (MCD) and M9 media. Metagenomic analysis revealed shifts in dominant bacteria, with Acidobacteria and Actinobacteria initially, and Chloroflexi, Firmicutes, and Proteobacteria later. Enzymatic profiling showed increased activity of key enzymes under metal-adapted conditions. Biolixiviation experiments revealed the highest metal recovery in mid-sized fractions at different conditions including the influence of microbial adaptation and the type of media used: Fe (47.2 %-53.0 %), Al (38.7 %-40.5 %), Cu (29.0 %-31.0 %), Ni (25.6 %-27.4 % in the largest fraction), and Co (40.1 %-41.0 %). Adapted consortia had higher recovery rates, offering a sustainable recycling route.

Knowledge Gaps in Quantifying the Climate Change Response of Biological Storage of Carbon in the Ocean

AbstractThe ocean is responsible for taking up approximately 25% of anthropogenic CO2 emissions and stores >50 times more carbon than the atmosphere. Biological processes in the ocean play a key role, maintaining atmospheric CO2 levels approximately 200 ppm lower than they would otherwise be. The ocean's ability to take up and store CO2 is sensitive to climate change, however the key biological processes that contribute to ocean carbon storage are uncertain, as are how those processes will respond to, and feedback on, climate change. As a result, biogeochemical models vary widely in their representation of relevant processes, driving large uncertainties in the projections of future ocean carbon storage. This review identifies key biological processes that affect how ocean carbon storage may change in the future in three thematic areas: biological contributions to alkalinity, net primary production, and interior respiration. We undertook a review of the existing literature to identify processes with high importance in influencing the future biologically‐mediated storage of carbon in the ocean, and prioritized processes on the basis of both an expert assessment and a community survey. Highly ranked processes in both the expert assessment and survey were: for alkalinity—high level understanding of calcium carbonate production; for primary production—resource limitation of growth, zooplankton processes and phytoplankton loss processes; for respiration—microbial solubilization, particle characteristics and particle type. The analysis presented here is designed to support future field or laboratory experiments targeting new process understanding, and modeling efforts aimed at undertaking biogeochemical model development.

The potential of pulsed electromagnetic field-generated shock waves for reducing microbial load and improving homogenization in raw milk

Milk is a highly nutritious food essential for human consumption. However, traditional thermal processing methods can reduce its nutritional value and cause unwanted changes. The use of shock waves produced by pulsed electromagnetic fields (PEMFs) has been explored as a means to reduce pathogenic microorganisms. The effect of shock wave treatment on microbial load and particle distribution in packaged fresh cow's milk was investigated. Additionally, the impact of shock wave treatment on Salmonella enterica counts in a bacterial suspension of phosphate-buffered saline (PBS) was evaluated, as this bacterium is a significant milkborne pathogen. Treatment with 1000 impulses from an electromagnetic shock wave generator resulted in a 0.7-log reduction in the total bacterial count of milk. In a separate experiment, a 300-impulse shock wave treatment applied to a Salmonella enterica suspension achieved a 3-log reduction in bacterial counts. Furthermore, shock wave treatment resulted in a decrease in milk particle size compared to untreated milk. Notably, the volume of milk used in this study aligns with commercially available packaged products, enhancing the experiment's industrial relevance. The use of PEMF to generate shock waves could provide a novel approach for future studies focused on reducing the microbial load of milk and improving its homogenization.

Enhancing nitrogen removal performance using immobilized aerobic denitrifying bacteria by modified polyvinyl alcohol/sodium alginate (PVA/SA)

Aerobic denitrification has emerged as a promising and efficient method for nitrogen removal from wastewater. However, the direct application of aerobic denitrifying bacteria has faced challenges such as low nitrogen removal efficiency, bacterial loss, and poor stability. To address these issues, this study developed a novel microbial particle carrier using NaHCO3-modified polyvinyl alcohol (PVA)/sodium alginate (SA) gel (NaHCO3-PVA/SA). This carrier exhibits several advantageous properties, including excellent mass transfer efficiency, favorable biocompatibility, convenient film formation, abundant biomass, and exceptional pollutant treatment capacity. The carrier was modified with 0.3% NaHCO3, 8.0% PVA, and 1.0% SA, resulting in a remarkable 3.4-fold increase in the average pore diameter and a 12.8% improvement in mass transfer efficiency. This carrier was utilized to immobilize the aerobic denitrifying bacterium Stutzerimonas stutzeri W-2 to enhance nitrogen removal (NaHCO3-PVA/SA@W-2), resulting in a NO3−-N removal efficiency of 99.06%, which was 21.39% higher than that without modification. Compared with the non-immobilized W-2, the degradation efficiency was improved by 43.70%. After five reuses, the NO3−-N and TN removal rates remained at 99% and 93.01%, respectively. These results provide a solid foundation for the industrial application of the modified carrier as an effective tool for nitrogen removal in large-scale wastewater treatment processes.

Distribution of polysaccharidic and proteinaceous gel−like particles in three cyclonic eddies in the Eastern Tropical North Atlantic

Transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP), two prominent classes of gel−like particles in the ocean primarily produced by phytoplankton, play crucial roles in ecological and biogeochemical processes, influencing microbial nutrition, growth, and particle aggregation. The distribution of these particles is intricately linked to the spatiotemporal dynamics of phytoplankton. Mesoscale cyclonic eddies (CEs) are known to stimulate phytoplankton growth and influence particle transport, but their effects on TEP and CSP remain to be determined. In the Eastern Tropical North Atlantic (ETNA), we examined three CEs: one off the Mauritanian coast during summer (Mau), one offshore during winter (Sal), and another near Brava island during winter. Mau and Brava CEs were in their intensification/maturity phase, while the Sal CE was in its decay phase. Both TEP and CSP concentrations correlated with primary productivity, but TEP increased with chlorophyll−a concentration, whereas elevated CSP coincided also with the highest abundance of pico−nanophytoplankton (<20 µm), mainly Synechococcus. Both gels exhibited a positive correlation with bacterial biomass production, indicating their consumption by heterotrophic bacteria. TEP total area in the epipelagic waters of all CEs (Mau, Brava, and Sal) was elevated compared to surrounding waters, with on average 4, 2.5, and 1.6−fold higher values, respectively. However, no significant difference in TEP size distribution was observed within any CEs and their surroundings. Similarly, CSP total area increased in the epipelagic waters of Mau and Brava CEs, with on average 5 and 2.4−fold higher values, respectively, compared to surrounding waters. CSP particles were notably larger in these two eddies, while the Sal CE showed no significant difference from surrounding waters in CSP abundance and size. Overall, TEP and CSP exhibited distinct responses to CEs, with increased concentrations during their intensification/maturation stage and remineralization dominating during their decaying stage.

Proton Pump Inhibitor Use and Complications of Cirrhosis Are Linked With Distinct Gut Microbial Bacteriophage and Eukaryotic Viral-Like Particle Signatures in Cirrhosis.

Proton pump inhibitors (PPIs) modulate the progression of cirrhosis to hepatic encephalopathy (HE) and can affect the bacterial microbiome. However, the impact of PPI on the virome in cirrhosis using viral-like particle (VLP) analysis is unclear. We determined the VLP in the stool microbiome in patients with cirrhosis cross-sectionally (ascites, HE, and PPI use analyzed) who were followed up for 6-month hospitalizations and through 2 clinical trials of PPI withdrawal and initiation. In a cross-sectional study, PPI users had greater ascites prevalence and 6-month hospitalizations, but VLP α diversity was similar. Among phages, PPI users had lower Autographviridae and higher Streptococcus phages and Herelleviridae than nonusers, whereas opposite trends were seen in ascites and HE. Trends of eukaryotic viruses (higher Adenoviridae and lower Virgaviridae/Smacoviridae) were similar for PPI, HE, and ascites. Twenty-one percent were hospitalized, mostly due to HE. α Diversity was similar in the hospitalized/nonhospitalized/not groups. Higher Gokushovirinae and lower crAssphages were related to hospitalizations such as HE-related cross-sectional VLP changes. As part of the clinical trial, PPIs were added and withdrawn in 2 different decompensated groups over 14 days. No changes in α diversity were observed. Withdrawal reduced crAssphages, and initiation reduced Gokushovirinae and Bacteroides phages. In cirrhosis, PPI use has a gut microbial VLP phage signature that is different from that in HE and ascites, and VLP changes are linked with hospitalizations over 6 months, independent of clinical biomarkers. Eukaryotic viral patterns were consistent across PPI use, HE, and ascites, indicating a relationship with the progression of cirrhosis. PPIs alone showed modest VLP changes with withdrawal or initiation. Distinct phage and eukaryotic viral patterns are associated with the use of PPIs in cirrhosis.

Organomineralization of dolomite in hypersaline microbial mats from Qatar sabkhas visualized by TEM & STXM

Deep insight into the low-temperature mineralization mechanism of dolomite in sediments has remained elusive. This issue is popularly termed “The Dolomite Problem” due to its multifactorial nature. Dolomite has been observed to mineralize in the exopolymeric substances produced by microbial mat communities (Bontognali et al. 2013), where productivity is high. One working hypothesis suggests that degrading organic matter in hypersaline environments releases the necessary component ions, increasing saturation with respect to dolomite (DiLoreto et al. 2019, Dupraz et al. 2009, Petrash et al. 2017). Other models suggest a dissolution-reprecipitation reaction of calcite to dolomite (Rivers 2023). High-resolution micro-spectroscopy techniques (such as transmission electron microscopy, TEM; and scanning transmission X-ray microscopy, STXM) can be used to determine chemical changes in crystals nucleating in a matrix, however to date very little studies have focused on observing dolomite mineralization at the nano-scale. The present study investigates microbial mats collected from hypersaline salt flats in the Persian gulf at micro- to nano-meter scales using high-spatial and -energy resolution TEM (Thermo Scientific Talos 200X at the Canadian Centre for Electron Microscopy) and STXM (PolLux Beamline at the Swiss Light Source at Paul Scherrer Institut), specifically to see changes in carbonate mineralization due to interactions with organic matter. C, Ca and O elemental maps of carbonate crystals were obtained with EDXS (energy-dispersive X-ray spectroscopy) in TEM. These crystals were also indexed by SAED (selected area electron diffraction in TEM). Fine spectral signatures (near-edge X-ray absorption fine structures, or NEXAFS) at the C K-edge (280-290 eV) and Ca L2,3-edge (344-356 eV) in STXM were used to determine the chemical identity of carbonate minerals and surrounding organic matter of the microbial mats. The results of the study show that dolomite nucleates in close association with the organic matter of the mats, where degradation is highest (defined in our adjacent study as the increase in C:N ratio). In TEM, polycrystalline dolomite is seen mineralizing in the matrix of the microbial mat organic material (Fig. 1). In STXM, the identity of the carbonate mineral changes from calcite on the outside to dolomite on the inside of the microbial mat particle (Fig. 2). In addition, our microsensor observations of elevated H2S concentrations, surface oxygenation from oxygenic phototrophy, high reduction potential, high organic carbon, high Mg:Ca ratio and high organic matter degradation (by C:N ratio) in each of the studied microbial mats confirms that the ideal dolomite mineralization conditions according to models of the dolomite problem are present in each case.

Evaluation of new photochemical systems for water disinfection by the integration of particle tracking into kinetic models for microbial inactivation

This work presents the development of a novel methodology for the simulation of photochemical processes for water disinfection using computational fluid dynamics (CFD). A new approach was implemented to calculate and visualise the disinfection performance as the microorganisms move along the photoreactor. Hydrodynamics and microorganism's statistical trajectories were computed using the discrete phase model, which also provides the distribution of microbial residence times. The distribution of radiation in the reactor was calculated using the discrete ordinate method. The local values of incident radiation were integrated over each statistical trajectory path to get the accumulated dose received for each microbial particle. The coupling in situ of the cumulative radiation dose with the inactivation kinetics allows monitoring of the disinfection process concurrently with the particle tracking. This methodology introduces significant advantages over the traditional estimation of the microorganism inactivation sequentially after calculating the dose histograms estimated from the statistical trajectories. The developed tool enables evaluating the photoreactor efficiency in each reactor position, a useful capability for optimising and scaling up complex geometries. It also allows the easy, intuitive visualisation of microbial inactivation trajectories, improving the understanding of the influence of the reactor features on the disinfection process. Application of this computational approach to two different photoreactor geometries using a virus as a representative target microbe is presented.

Deconvolving mechanisms of particle flux attenuation using nitrogen isotope analyses of amino acids

AbstractParticulate organic matter settling out of the euphotic zone is a major sink for atmospheric carbon dioxide and serves as a primary food source to mesopelagic food webs. Degradation of this organic matter encompasses a suite of mechanisms that attenuate flux, including heterotrophic metabolic processes of microbes and metazoans. The relative contributions of microbial and metazoan heterotrophy to flux attenuation, however, have been difficult to determine. We present results of compound specific nitrogen isotope analysis of amino acids of sinking particles from sediment traps and size‐fractionated particles from in situ filtration between the surface and 500 m at Ocean Station Papa, collected during NASA EXPORTS (EXport Processes in the Ocean from RemoTe Sensing). With increasing depth, we observe: (1) that, based on the δ15N values of threonine, fecal pellets dominate the sinking particle flux and that attenuation of downward particle flux occurs largely via disaggregation in the upper mesopelagic; (2) an increasing trophic position of particles in the upper water column, reflecting increasing heterotrophic contributions to the nitrogen pool and the loss of particles via remineralization; and (3) increasing δ15N values of source amino acids in submicron and small (1–6 μm) particles, reflecting microbial particle solubilization. We further employ a Bayesian mixing model to estimate the relative proportions of fecal pellets, phytodetritus, and microbially degraded material in particles and compare these results and our interpretations of flux attenuation mechanisms to other, independent methods used during EXPORTS.

Seasonal dynamics in bacterial communities of closed-cage broiler houses.

The bacteria contained in air aerosols from poultry houses are closely connected to animal health and production. This study aimed to investigate the seasonal factors on microbial aerosol concentration, particle size and bacterial spectrum composition inside a closed-cage broiler house. Then, 16S rDNA sequencing technology was applied to analyze the characteristics of bacterial abundance and diversity. The results indicated that the concentration of bacterial aerosol in the broiler house varied significantly in different seasons, with a concentration range of 5.87-15.77 × 103 CFU/m3, and the highest and lowest concentrations in the summer and winter, respectively. Microbiological analysis showed that the proportion of Gram-negative bacteria in autumn was significantly higher than that in summer (P < 0.05). In addition, the floral structure of potential pathogenic bacterial genera also differed by season. Escherichia-Shigella, Streptococcus, Acinetobacter, Pseudomonas were identified in the bacterial aerosols. Importantly, the relative abundance of Firmicutes in spring and autumn was much higher. In contrast, the relative abundance of Proteobacteria in spring and autumn was lower than that in summer and winter. Altogether, results revealed the effects of seasonal factors on the diversity and abundance of bacteria and the distribution characteristics of major opportunistic pathogens in the air of closed-cage broiler houses. These results will provide important information for exploring the potential risk of aerosols from poultry houses all four seasons.

Direct In-Situ Capture, Separation and Visualization of Biological Particles with Fluid-Screen in the Context of Venus Life Finder Mission Concept Study

Evidence of chemical disequilibria and other anomalous observations in the Venusian atmosphere motivate the search for life within the planet’s temperate clouds. To find signs of a Venusian aerial biosphere, a dedicated astrobiological space mission is required. Venus Life Finder (VLF) missions encompass unique mission concepts with specialized instruments to search for habitability indicators, biosignatures and even life itself. A key in the search for life is direct capture, concentration and visualization of particles of biological potential. Here, we present a short overview of Fluid-Screen (FS) technology, a recent advancement in the dielectrophoretic (DEP) microbial particle capture, concentration and separation. Fluid-Screen is capable of capturing and separating biochemically diverse particles, including multicellular molds, eukaryotic cells, different species of bacteria and even viruses, based on particle dielectric properties. In this short communication, we discuss the possible implementation of Fluid-Screen in the context of the Venus Life Finder (VLF) missions, emphasizing the unique science output of the Fluid-Screen instrument. FS can be coupled with other highly sophisticated instruments such as an autofluorescence microscope or a laser desorption mass spectrometer (LDMS). We discuss possible configurations of Fluid-Screen that upon modification and testing, could be adapted for Venus. We discuss the unique science output of the Fluid-Screen technology that can capture biological particles in their native state and hold them in the focal plane of the microscope for the direct imaging of the captured material. We discuss the challenges for the proposed method posed by the concentrated sulfuric acid environment of Venus’ clouds. While Venus’ clouds are a particularly challenging environment, other bodies of the solar system, e.g., with liquid water present, might be especially suitable for Fluid-Screen application.

Single viable fungal aerosol particle discerning using naked eye assisted with laser trapping and microwaving

Viable microbial aerosol detection remains a grand challenge. Here, we pioneered a new system that integrates laser trapping and microwave irradiation for online discerning of single viable microbial aerosol particle through naked eye. To test the system, three fungal species Aspergillus niger, Aspergillus oryzae, and Trichoderma harzianum and three non-biological particles such as MnO2, active carbon, and Fe3O4 were suspended and laser trapped in the air inside a house-made glass cube. When microwave irradiated, some fungal spores were observed to rapidly escape from the trapping and even burst with abrupt morphology changes under a longer irradiation. In contrast, others similar to those non-biological particles were shown to behave differently with little morphology change without the cell burst. For all particles tested, microwave irradiation resulted in particle movement within the trapping region, and a particle trapping was then re-established in a new location. Depending on particle type and irradiation time, light scattering properties also differed between biological and non-biological particles when irradiated. Terminating the microwave irradiation was observed to render the non-biological particles to return where they were being laser trapped. Using the developed system, we have demonstrated the viable microbial aerosol detection using naked eye by simply observing the morphology changes and cell burst upon the laser trapping and microwave irradiation. A portable version of the system was further developed and successfully tested for discerning viable aerosol cells from non-biological ones. Further efforts on this development could lead to a new generation of bioaerosol detection strategy.

Probabilistic fecal pollution source profiling and microbial source tracking for an urban river catchment

We developed an innovative approach to estimate the occurrence and extent of fecal pollution sources for urban river catchments. The methodology consists of 1) catchment surveys complemented by literature data where needed for probabilistic estimates of daily produced fecal indicator (FIBs, E. coli, enterococci) and zoonotic reference pathogen numbers (Campylobacter, Cryptosporidium and Giardia) excreted by human and animal sources in a river catchment, 2) generating a hypothesis about the dominant sources of fecal pollution and selecting a source targeted monitoring design, and 3) verifying the results by comparing measured concentrations of the informed choice of parameters (i.e. chemical tracers, C. perfringensspores, and host-associated genetic microbial source tracking (MST) markers) in the river, and by multi-parametric correlation analysis. We tested the approach at a study area in Vienna, Austria. The daily produced microbial particle numbers according to the probabilistic estimates indicated that, for the dry weather scenario, the discharge of treated wastewater (WWTP) was the primary contributor to fecal pollution. For the wet weather scenario, 80–99 % of the daily produced FIBs and pathogens resulted from combined sewer overflows (CSOs) according to the probabilistic estimates. When testing our hypothesis in the river, the measured concentrations of the human genetic fecal marker were log10 4 higher than for selected animal genetic fecal markers. Our analyses showed for the first-time statistical relationships between C. perfringens spores (used as conservative microbial tracer for communal sewage) and a human genetic fecal marker (i.e. HF183/BacR287) with the reference pathogen Giardia in river water (Spearman rank correlation: 0.78–0.83, p < 0.05. The developed approach facilitates urban water safety management and provides a robust basis for microbial fate and transport models and microbial infection risk assessment.

Cover Image, Volume 119, Number 8, August 2022

The cover image is based on the Article An integrated and continuous downstream process for microbial virus-like particle vaccine biomanufacture by Lukas Gerstweiler et al., https://doi.org/10.1002/bit.28118.

An integrated and continuous downstream process for microbial virus-like particle vaccine biomanufacture.

In this study, we present the first integrated and continuous downstream process for the production of microbial virus‐like particle vaccines. Modular murine polyomavirus major capsid VP1 with integrated J8 antigen was used as a model virus‐like particle vaccine. The integrated continuous downstream process starts with crude cell lysate and consists of a flow‐through chromatography step followed by periodic counter‐current chromatography (PCC) (bind‐elute) using salt‐tolerant mixed‐mode resin and subsequent in‐line assembly. The automated process showed a robust behavior over different inlet feed concentrations ranging from 1.0 to 3.2 mg ml−1 with only minimal adjustments needed, and produced continuously high‐quality virus‐like particles, free of nucleic acids, with constant purity over extended periods of time. The average size remained constant between 44.8 ± 2.3 and 47.2 ± 2.9 nm comparable to literature. The process had an overall product recovery of 88.6% and a process productivity up to 2.56 mg h−1 mlresin −1 in the PCC step, depending on the inlet concentration. Integrating a flow through step with a subsequent PCC step allowed streamlined processing, showing a possible continuous pathway for a wide range of products of interest.

Riverine microplastic and microbial community compositions: A field study in the Netherlands

Plastic pollution in aquatic environments, particularly microplastics (<5 mm), is an emerging health threat. The buoyancy, hydrophobic hard surfaces, novel polymer carbon sources and long-distance transport make microplastics a unique substrate for biofilms, potentially harbouring pathogens and enabling antimicrobial resistance (AMR) gene exchange. Microplastic concentrations, their polymer types and the associated microbial communities were determined in paired, contemporaneous samples from the Dutch portion of the river Rhine. Microplastics were collected through a cascade of 500/100/10 μm sieves; filtrates and surface water were also analysed. Microplastics were characterized with infrared spectroscopy. Microbial communities and selected virulence and AMR genes were determined with 16S rRNA-sequencing and qPCR. Average microplastic concentration was 213,147 particles/m3; polyamide and polyvinylchloride were the most abundant polymers. Microbial composition on 100–500 μm samples differed significantly from surface water and 10–100 μm or smaller samples, with lower microbial diversity compared to surface water. An increasingly ‘water-like’ microbial community was observed as particles became smaller. Associations amongst specific microbial taxa, polymer types and particle sizes, as well as seasonal and methodological effects, were also observed. Known biofilm-forming and plastic-degrading taxa (e.g. Pseudomonas) and taxa harbouring potential pathogens (Pseudomonas, Acinetobacter, Arcobacter) were enriched in certain sample types, and other risk-conferring signatures like the sul1 and erm(B) AMR genes were almost ubiquitous. Results were generally compatible with the existence of taxon-selecting mechanisms and reduced microbial diversity in the biofilms of plastic substrates, varying over seasons, polymer types and particle sizes. This study provided updated field data and insights on microplastic pollution in a major riverine environment.

Movement Mechanisms and Numerical Simulation of Virus-containing Exhaled Droplets

The problem of viral and microbial contamination has received extensive and high attention from scholars at home and abroad. A great deal of information and research has demonstrated that droplets containing organisms such as viruses and bacteria can be airborne, so it is extremely important to study the movement and transmission patterns of the particles. Human coughing and sneezing are the main sources of viral droplets and are the focus of this paper. This topic starts with a theoretical approach to investigate the propagation law of microbial aerosols in the air, combined with the characteristics of droplets, to establish a model of microbial particle dispersal. And based on the Lagrangian method, the model is simplified and the 4th order standard Runge-Kutta algorithm is used to numerically solve the differential equations based on the Matlab platform, so as to analyse the effects of factors such as jet velocity, ambient wind speed and the size of the exhaled virus particles occurring on the particle motion. The evaporation of particles also has a relatively large effect on the motion of smaller sized particles, which after complete evaporation will will float in the air and will no longer hit the ground. Ultimately, the analysis of particle movement distances leads to recommendations for the prevention of airborne infectious disease transmission.

Does a mobile dust-containment cart reduce the risk of healthcare-associated fungal infections during above-ceiling work?

Immunocompromised patients are at risk for infections due to above-ceiling activities in hospitals. Mobile dust-containment carts are available as environmental controls, but no published data support their efficacy. Using microbial air sampling and particle counts, we provide evidence of reduced risk of fungal exposure during open ceiling activities.

Modelling of Escherichia coli removal by a low-cost combined drinking water treatment system

AbstractThis work presents mathematical modelling of Escherichia coli (E.coli) removal by a multi-barrier point-of-use drinking water system. The modelled system is a combination of three treatment stages: filtration by geotextile fabric followed by filtration and disinfection by silver-coated ceramic granular media (SCCGM) then granular activated carbon (GAC) filtration. The presented models accounted for removal mechanisms by each treatment stage. E.coli was modelled as a microbial particle. E.coli inactivation by SCCGM was modelled using the Chick's, Chick-Watson, Collins-Selleck and complete mix system bacterial inactivation kinetic models, which were considered adequately representative for describing the removal. Geotextile removal was modelled using colloidal filtration theory (CFT) for hydrosol deposition in fibrous media. The filtration removal contributions by the SCCGM and GAC were modelled using CFT for removal of colloidal particles by granular media. The model results showed that inactivation by silver in the SCCGM was the main bacterial removal mechanism. Geotextile and GAC also depicted appreciable removals. The theoretical modelling approach used is important for design and optimization of the multi-barrier system and can support future research in terms of material combinations, system costs, etc. Collector diameter, particle size, filtration velocity and contact time were identified as critical parameters for E.coli removal efficiency.

Investigation of Microbial Contamination and Physicochemical Properties of Compounded Medications in Pharmacies

Aims: Any pharmaceutical product made in pharmacy, hospital or factory may be contaminated with microbes. This contamination can originate from raw materials or during production. Hence, it is important to study the physical and chemical properties and stability of compounded drugs. Methods &amp; Materials: In this study, first a specific sample of prescribed medication was ordered from 63 pharmacies in Yazd, Iran. After collecting the samples, the amount of microbial contamination, viscosity and particle size distribution and their stability were investigated and their results were compared to the standard levels. Findings: Based on the results, 31.7% of the samples had discoloration and 23.8% showed creaming phenomenon. In terms of particle size distribution, 57.1% of the samples had a 20-40 μm particle size and 49.2% had a viscosity equal to 2500-3000 centipoise. Regarding stability, 12.6% of the samples underwnet phase change at 30-40°C. About of the amount of hydroquinone in samples, 35% had acceptable amount. In 23.8% of the samples, fungal infection was observed. Conclusion: Contrary to a popular belief that the compounded medicines produced in pharmacies have microbial contamination, the results of this study showed that the microbial contamination of these compounded medications is low.