Removal Of Microorganisms Research Articles

Solar-driven free chlorine advanced oxidation process for simultaneous removal of microcontaminants and microorganisms in natural water at pilot-scale

Contamination of natural water (NW) by emerging contaminants has been widely pointed out as one of the main challenges to ensure high-quality drinking water. Thus, the effectiveness of a solar-driven free chlorine advanced oxidation process simultaneously investigating the elimination of six organic microcontaminants (OMCs) and three bacteria from NW at a pilot-scale was evaluated in this study. Firstly, the solar/free chlorine process was studied at lab-scale using a solar simulator to evaluate the effect of free chlorine concentration (0.5–10 mg L−1) on OMC degradation and generation of toxic oxyanions (e.g., ClO3− ions). Thus, the best free chlorine concentration observed was applied for the simultaneous removal of OMCs and pathogens under natural solar light at pilot scale. At lab-scale, the solar/free chlorine (2.5 mg L−1) process achieved 80% of total degradation in 5 min (1.4 kJ L−1 of accumulative UV energy) with an oxidant consumption of 0.3 mg L−1 and without ClO3− generation. Similar results were attained under natural solar irradiation at a pilot-scale. For all bacteria strains, the legally required detection limit (DL = 1 CFU 100 mL−1) for reclaimed water reuse was attained in a short contact time. Still, more importantly, the solar/free chlorine (2.5 mg L−1) process effectively avoided the possible bacterial regrowth in the post-treated sample after six days. Finally, the combination of free chlorine with solar irradiation provided a simple and energy-efficient process for OMC and bacteria removal in NW at a pilot-scale.

Comparative Study between Zn and Cu Nano Ferrite in Removal of Heavy Metals and Microorganisms from Water

The effect of Nano composite materials (CuFe2O4 and ZnFe2O4) was studied for removal of heavy metals (Cd (II) and Pb (II)) from wastewater by batch adsorption method and explain their effect on the antimicrobial effectiveness on gram positive and negative bacteria. Nano composite materials were characterized by XRD where the result indicates that the average crystallite sizes were around 36.19 nm for ZnFe2O4 and 12.22 nm for CuFe2O4.The effect of contact time, adsorbent dose, pH and type of adsorbents was used to find the optimum condition for removal of Cd(II) and Pb(II) ions .The equilibrium adsorption data was good fitted to the Langmuir and Freundlich isotherm models, and the pseudo first-order kinetic model showed the excellent fit in adsorption equilibrium capacity. The best pH used for removal was 7. The good removal reaches at the time 45 min for cadmium and need more time for lead. When increasing dosage of adsorbents, the removal efficiency increases. Freundlich and Langmuir isotherm gave the best fit experimental data. Also, antibacterial effects of this nano particles demonstrated the effect of CuFe2O4 NPs on bacteria more than used ZnFe2O4 NPs, and the percentage of bacterial death was increased according to increase the concentration of this materials.

Evaluation of Anti-microbial activity of graphene oxide-TiO2 nanocomposites with variable compositions

The anti-fungal activity towards the elimination of the fungus Candida albicans and Candida rugosa and anti-bacterial activity for the removal of gram-negative Escherichia coli, gram-positive Staphylococcus aurues bacteria were evaluated with the graphene oxide-TiO2 nanocomposites. These nanocomposites contain a fixed weight of titania with variable weight % of graphene oxide (1%, 5 %, 10 %, 15%). The photocatalytic activity of these composites has been evaluated earlier towards the degradation of different organic dyes. In the present work, their biological activity was determined. It was observed that the micro-organisms removal was higher in the presence of graphene oxide than with the bare nanotitania particles. Further, the removal has increased with increase in the wt.% of graphene oxide in the nanocomposites. Superior anti-microbial activity was shown by composite with 10 wt.% graphene oxide. In the studies, anti-bacterial performance was observed to be greater than the anti-fungal activity with the nanocomposites.

Elucidating the intensifying effect of introducing influent to an anaerobic side-stream reactor on sludge reduction of the coupled membrane bioreactors

Three anoxic/oxic membrane bioreactors (AO-MBRs) coupled with the anaerobic side-stream reactor (ASSR) with different influent flow distribution ratios (IFDRs) were assessed to elucidate how IFDR in the ASSR affected pollutants removal, sludge reduction, membrane fouling, and potential co-occurrence network of microorganisms. When the IFDR in the ASSR was increased from 0% (ASSR0-MBR), to 25% (ASSR25-MBR) and 75% (ASSR75-MBR), chemical oxygen demand removal was enhanced and nutrient removal was comparable. Compared to ASSR0-MBR, ASSR25- and ASSR75-MBR further improved the sludge reduction by 7.6% and 10.9%, respectively. ASSR25-MBR followed cake-complete model due to the weak membrane surface scouring and high concentration of extracellular polymeric substances, while ASSR0- and ASSR75-MBR fitted cake-standard model. The increased IFDR in the ASSR boosted the relative abundance of hydrolytic and slow-growing bacteria. The co-occurrence networks of sludge reduction, nutrient removal and membrane fouling propensity indicated that the symbiotic relationships were dominant.

CQDs-MoS2 QDs loaded on Dendritic fibrous Nanosilica/Hydrophobic waterborne polyurethane acrylate for antibacterial coatings

Since bacterial infections are the cause of many diseases, death, and disability, considerable attention has been paid to the preparation of antibacterial surfaces. Anti-adhesive and bactericidal synergistic surfaces show promising antimicrobial applications due to the removal and killing effect of microorganisms. Herein, we proposed a leather coating surface with hydrophobic and photocatalytic antibacterial properties. Dendritic fibrous nanosilica (DFNS) loaded with carbon quantum dots (CQDs) and MoS2 QDs (DFNS@CQDs-MoS2) nanoparticles were successfully prepared, which exhibited excellent photocatalytic antibacterial activity. Specifically, the DFNS@CQDs-MoS2 nanoparticles exhibited antibacterial activities of 99.98%, 95.35%, and 99.99% against Escherichia coli, Staphylococcus aureus, and Aspergillus niger, respectively. Then, hydrophobic waterborne polyurethane acrylate (HWPUA) was developed, which exhibited enhanced bacterial adhesion resistance. Furthermore, the HWPUA/DFNS@CQDs-MoS2 coating completely inactivated the residual bacterial cells. Therefore, the synergistic antibacterial coatings developed in this work could have potential applications as antibacterial surfaces.

Managing microbes

Managing microbes

H2O2-assisted photocatalysis induced by SPR of BiQDs anchored on BiVO4 for the production of hydroxyl radicals in seawater

Ballast water is an essential component of nautical navigation, however, the microorganisms present in the water may be an environmental hazard. Therefore, the decontamination of ballast water has been widely studied. The anchoring of metal nanoparticles with plasmonic properties into semiconductors is an effective way to enhance their photocatalytic activity for the inactivation of marine microorganisms in ballast water. In this paper, we describe the successful synthesis of BiQDs/BiVO4 via a facile solvothermal method and evaluated their capacity to inactivate marine microorganisms under visible light irradiation. The results showed that 3%BiQDs/BiVO4 exhibited greatest photocatalytic sterilization efficiency with the low concentration of H2O2 present in real seawater. Further results revealed that the BiQDs had a diameter of approximately 5.1 nm and were distributed randomly on BiVO4, and that the SPR effect of BiQDs enhanced the utilization of visible light. The hydroxyl radical was proven to be the main active species and the addition of H2O2 promoted the generation of ·OH to achieve the efficient decontamination of ballast water. This study may provide a potential route for the photocatalytic removal of marine microorganisms and ballast water tank protection.

Ultraviolet Radiation to control Bacteria in oil well injection water

Biocorrosion is a phenomenon that strongly affects the integrity of the materials used in the oil and gas industry. Different types of biocides are currently used to control bacteria in industrial water; however, they have disadvantages such as microbial resistance to these chemical compounds and possible impact on biodiversity due to eventual contamination of natural water. There are several alternatives for the elimination or control of bacteria, among which one is the use of type C ultraviolet (UV-C) radiation. Nevertheless, the use of these micro-organism removal systems could be affected by water quality and its efficiency can be improved by using LED diodes of lower energy consumption and greater versatility in exposure to high temperatures. This work was aimed to evaluate the use of such radiation as a strategy for the control and/or elimination of sulfate reducing bacteria (SRB), and acid producing bacteria (APB) present in both corrosion and souring processes. For this purpose, injection water from oil and gas industry and a dynamic system which flow variation enabled the evaluation of different water exposure times to UV-C light (1-20 minutes) were used. Efficiencies ranging between 99-100% were achieved in the elimination of SRB and APB from produced water measured by two different techniques, selective culture media for these microbial populations, and qPCR detecting a specific gene from the SRB population.

Survival of the fittest: Prokaryotic communities within a SWRO desalination plant

Water scarcity is known to affect 40% of the global population. By 2030, it is estimated that 700 million people will potentially become displaced due to drought. Seawater reverse osmosis (SWRO) desalination is recognised as one of the most cost effective and efficient methods to produce freshwater. However, biofouling of the SWRO membranes is detrimental to the efficacy of the desalination plants. In this study, the bacterial community composition within the pre-treatment system at Penneshaw SWRO desalination plant (Kangaroo Island, Australia) and the biological fouling parameters on the SWRO membranes were characterised. Membrane autopsies were undertaken on stages 1 and 2 positioned membranes that were operational for two and four years. Results showed that the pre-treatment system allowed for the removal of microorganisms from the water, however niche communities were able to establish and proliferate within the plant due to environmental adaption. The communities associated with the SWRO membranes were stable and had the ability to flourish on the membranes within biofilms. This study provides insights into the community structure within the pre-treatment system of the desalination plant, as well as on the SWRO membranes and examines how they impact on the performance of the plant.

Inactivation, removal, and regrowth potential of opportunistic pathogens and antimicrobial resistance genes in recycled water systems

With two thirds of the global population living in areas affected by water scarcity, wastewater reuse is actively being implemented or explored by many nations. There is a need to better understand the efficacy of recycled water treatment plants (RWTPs) for removal of human opportunistic pathogens and antimicrobial resistant microorganisms. Here, we used a suite of probe-based multiplex and SYBR green real-time PCR assays to monitor enteric opportunistic pathogens (EOPs; Acinetobacter baumannii, Arcobacter butzlieri, Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, Legionella spp., Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella Enteritidis, Streptococcus spp.) and antimicrobial resistance genes (ARGs; qnrS, blaSHV, blaTEM, blaGES, blaKPC, blaIMI, blaSME, blaNDM, blaVIM, blaIMP, blaOXA-48-like, mcr-1 and mcr-3) of key concern from an antimicrobial resistance (AMR), waterborne and foodborne disease perspective. The class 1 integron-integrase gene (intl1) was quantified as a proxy for multi-drug resistance. EOPs, intl1 and ARGs absolute abundance (DNA and RNA) and metabolic activity (RNA) was assessed through three RWTPs with differing treatment trains. Our results indicate that RWTPs produced high quality recycled water for non-potable reuse by removing >95% of EOPs and ARGs, however, subpopulations of EOPs and ARGs survived disinfection and demonstrated potential to become actively growing members of the recycled water and distribution system microbiomes. The persistence of functional intl1 suggests that significant genetic recombination capacity remains in the recycled water, along with the likely presence of multi-drug resistant bacteria. Results provide new insights into the persistence and growth of EOPs, and prevalence and removal of ARGs in recycled water systems. These data will contribute towards the emerging evidence base of AMR risks in recycled water to inform quantitative risk-based policy development regarding water recycling schemes.

Polymeric Membrane with Nanomaterial’s for Water Purification: A Review

This review summarizes the work principles used for polymer membrane in water treatment. The performance of traditional polymeric films was improved after adding some nanometals such as nano silver AgNPs and gold AuNP’s and nanomaterials, especially the use of titanium dioxide, carbon nanotube and zinc oxide (TiO2, CNT, ZnO, …etc.), which is available, cheap and environmentally friendly. The theoretical aspects of the polymeric films coated with nanomaterials and the use of the advanced water treatment, removal of microorganisms, chemical compounds, heavy metals, and others are presented. The use of nanomaterials has helped to enhance the water resistance ability, suppress the accumulation of pollutants and contamination, enhance the reject efficiency and improve mechanical properties and thermal stability. Thus, the goal of the present work is to provide updated information regarding the membranes of the new nanocomposites (NC) and their contribution to water treatment applications.

Widespread applicability of bacterial cellulose-ZnO-MWCNT hybrid membranes

Abstract The novel photoactive membranes have grabbed the attention in the field of environmental protection by employing wastewater treatments and the removal of microorganisms or organic pollutants from wastewater. Here we present a promising self-supported photoactive hybrid membrane for future antimicrobial and water treatment applications. In this study, the efficiency of bacterial cellulose (BC) - zinc oxide (ZnO) - multi walled carbon nanotube (MWCNT) hybrid membranes in the adsorption and photocatalytic degradation of methylene blue (MB) under UV radiation and the removal of Escherichia coli (E. coli) was investigated. It was found that the photocatalytic efficiency is strongly dependent on both the preparation method and the amount of ZnO-MWCNT additives loaded into the hybrid membranes. The characterization of BC-ZnO-MWCNT membranes was done using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and X-ray micro computed tomography (μCT) to study the morphological and porosity aspect of the prepared-membranes. The promising results of this study could provide a new pathway in the field of photocatalysed-based water treatment technology by the application of hybrid membranes.

Effect of concentration on virus removal for ultrafiltration membrane in drinking water production

Removal of pathogenic microorganisms as viruses during drinking water production was evaluated by ultrafiltration. Two enteric viruses (ADV 41 and CV-B5) were compared to the MS2 bacteriophage, largely used in literature and by membrane producers as enteric virus surrogate. The effect of feed concentration of viruses on the ultrafiltration efficiency has been assessed. For the three viruses, low retentions about 1 log were observed at the lowest concentrations. At higher concentrations, an increase of removal up to 3.0 log for CV-B5 and MS2 phage and 3.5 log for ADV 41 was observed. These results highlight the potential overestimation of UF efficiency during laboratory experiments realized at high concentrations, compared to low concentrations found in environmental resources used for drinking water production. Virus removals with Evian water and real groundwater were compared and groundwater achieved similar or slightly higher removals for the three viruses. Finally, impact of membrane ageing after chlorine exposure was checked. It was observed that membrane degradations, visible by a water permeability increase with exposure dose did not affect the removal of viruses at low feed concentrations.

Verification and Optimization of an Ultra-Low Volume (ULV) Sprayer Used for the Inactivation of Indoor Total Bacteria

Physical and chemical cleaning for the removal of indoor microorganisms, which can cause allergic reactions and respiratory diseases, is labor-intensive and time-consuming. An ultra-low volume (ULV) sprayer, a newly introduced device to inactivate pathogenic microorganisms, allows the disinfectant particles to reach hard-to-reach spaces indoors and is more cost-effective than the existing methods. However, few studies have been conducted to verify the efficiency of the ULV sprayer. Here, we verified the disinfection efficiency of the ULV sprayer for inactivating total bacteria present on indoor surfaces, considering the factors affecting bacteria inactivation, and presented the optimal ULV sprayer usage conditions to achieve the highest disinfection efficiency depending on room size. The total bacteria removal efficiency was high (range: 0.56–2.46 log10 reductions), including hard-to-reach spaces. A response surface model was developed to identify the individual and interactive effects of the disinfectant concentration, spray amount, and room size on total bacteria disinfection efficiency. These three variables had interactive effects on the total bacteria disinfection efficiency. The experimental data were fitted to a second-order polynomial model, with high coefficients of determination (R2) for all models (R2 > 0.82). The optimum conditions were a spray amount of 3.08–6.40 L in 160 m3, 3.78–7.22 L in 230 m3, and 5.68–8 L in 300 m3 surface area when using dilution rates of 100 times. These conditions predicted a bacterial disinfection efficiency of >1.10 log10 reductions (92%) on all surfaces. Our results clearly indicate that the ULV sprayer effectively inactivates total bacteria present on indoor surfaces.

Organic load removal and microbial disinfection of raw domestic sewage using SrSnO3/g-C3N4 with sunlight.

Sewage treatment and water reuse are, undoubtedly, one of the main points on scientific agenda of the 21st century. Many technologies for sewage treatment are available; however, it is still as an open issue that deserves much attention in order to facilitate their application, develop more effective methods and propose alternative treatment for unusual situations. Developing high performance materials for sewage treatment fits the idea of the development of efficient and alternative methods for microorganism removal and the high organic load of wastewater and is of fundamental importance. In this paper, a heterojunction with perovskite-type strontium stannate (SrSnO3) and graphitic carbon nitride (g-C3N4) - SrSnO3/g-C3N4 - was synthesized and used for photocatalytic treatment of domestic sewage using only sunlight. Results were accompanied by assessing the total organic carbon decrease and removal of pathogenic microorganisms. X-ray diffraction and X-ray excited photoelectron spectroscopy demonstrated that a heterostructure was successfully formed and photocatalytic tests showed an important activity in the visible range, i.e., under sunlight. Exposing raw sewage to 240 min (from 11 a.m. until 3 p.m.) in the presence of SrSnO3/g-C3N4, led to a 56.1% mineralization. This process was 2.5 more efficient than photolysis under sunlight. Moreover, the treated sewage showed no coliform growth (either fecal or total) or heterotrophic bacteria. This simple treatment makes sewage suitable and safe for reuse, for example, for agriculture purposes according to Brazilian regulations criteria and could be an alternative for isolated areas in which sewage treatment plants are not available.

Antimicrobial stewardship strategies in wound care: evidence to support the use of dialkylcarbamoyl chloride (DACC)- coated wound dressings.

Traditionally, infections are treated with antimicrobials (for example, antibiotics, antiseptics, etc), but antimicrobial resistance (AMR) has become one of the most serious health threats of the 21st century (before the emergence of COVID-19). Wounds can be a source of infection by allowing unconstrained entry of microorganisms into the body, including antimicrobial-resistant bacteria. The development of new antimicrobials (particularly antibiotics) is not keeping pace with the evolution of resistant microorganisms and novel ways of addressing this problem are urgently required. One such initiative has been the development of antimicrobial stewardship (AMS) programmes, which educate healthcare workers, and control the prescribing and targeting of antimicrobials to reduce the likelihood of AMR. Of great importance has been the European Wound Management Association (EWMA) in supporting AMS by providing practical recommendations for optimising antimicrobial therapy for the treatment of wound infection. The use of wound dressings that use a physical sequestration and retention approach rather than antimicrobial agents to reduce bacterial burden offers a novel approach that supports AMS. Bacterial-binding by dressings and their physical removal, rather than active killing, minimises their damage and hence prevents the release of damaging endotoxins. Our objective is to highlight AMS for the promotion of the judicious use of antimicrobials and to investigate how dialkylcarbamoyl chloride (DACC)-coated dressings can support AMS goals. MEDLINE, Cochrane Database of Systematic Reviews, and Google Scholar were searched to identify published articles describing data relating to AMS, and the use of a variety of wound dressings in the prevention and/or treatment of wound infections. The evidence supporting alternative wound dressings that can reduce bioburden and prevent and/or treat wound infection in a manner that does not kill or damage the microorganisms (for example, by actively binding and removing intact microorganisms from wounds) were then narratively reviewed. The evidence reviewed here demonstrates that using bacterial-binding wound dressings that act in a physical manner (for example, DACC-coated dressings) as an alternative approach to preventing and/or treating infection in both acute and hard-to-heal wounds does not exacerbate AMR and supports AMS. Some wound dressings work via a mechanism that promotes the binding and physical uptake, sequestration and removal of intact microorganisms from the wound bed (for example, a wound dressing that uses DACC technology to successfully prevent/reduce infection). They provide a valuable tool that aligns with the requirements of AMS (for example, reducing the use of antimicrobials in wound treatment regimens) by effectively reducing wound bioburden without inducing/selecting for resistant bacteria.

Inhibition of microbial production of the malodorous substance isovaleric acid by 4,4' dichloro 2-hydroxydiphenyl ether (DCPP).

Human body malodour is a complex phenomenon. Several types of sweat glands produce odorless secretions that are metabolized by a consortium of skin‐resident microorganisms to a diverse set of malodorous substances. Isovaleric acid, a sweaty‐smelling compound, is one major malodorous component produced by staphylococci with the skin‐derived amino acid L‐leucine as a substrate. During wearing, fabrics are contaminated with sweat and microorganisms and high humidity propagates growth and microbial malodour production. Incomplete removal of sweat residues and microorganisms from fabrics during laundry with bleach‐free detergents and at low temperatures elevate the problem of textile malodour. This study aimed to analyze the inhibitory effect of the antimicrobial 4,4ʹ dichloro 2‐hydroxydiphenyl ether (DCPP) on the formation of isovaleric acid on fabrics. Therefore, GC‐FID‐ and GC–MS‐based methods for the analysis of isovaleric acid in an artificial human sweat‐mimicking medium and in textile extracts were established. Here, we show that antimicrobials capable to deposit on fabrics during laundry, such as DCPP, are effective in growth inhibition of typical malodour‐generating bacteria and prevent the staphylococcal formation of isovaleric acid on fabrics in a simple experimental setup. This can contribute to increased hygiene for mild laundry care approaches, where bacterial contamination and malodour production represent a considerable consumer problem.

Benefits in the valorization of sewage sludge and wine vinasse via a two-stage acidogenic-thermophilic and methanogenic-mesophilic system based on the circular economy concept

Anaerobic digestion can be considered as a promising solution to solve the problems, increase of energy demand and waste generation, caused by the increasing population growth. The main objective of this work was to study anaerobic codigestion of sewage sludge and wine vinasse in a two-stage acidogenic-thermophilic and methanogenic-mesophilic system within the framework of the circular economy. This system was compared with anaerobic codigestion in single-stage reactors (thermophilic and mesophilic conditions) in order to assess the potential benefits of a two-stage system in terms of energy production and pathogenic microorganisms removal. Hydrogen was only produced in the first stage of the two-stage system (22.90 mL H2/gVSadded). Both the highest specific methane production (212.56 mL CH4/gVSadded) and electricity generation were obtained in the second stage of the two-stage system. The electrical energy generated was estimated at 14.03 kWh/t fed, which represents 5% of the total energy used by Guadalete wastewater treatment plant (SW Spain). All the systems achieved lower values of E. coli and Salmonella than those stipulated by legislation regarding Class A biosolids quality, therefore digestate can be used as fertilizer.

Chlorine Rechargeable Halamine Biocidal Alginate/Polyacrylamide Hydrogel Beads for Improved Sanitization of Fresh Produce.

Traditional fresh produce washing systems mainly rely on mechanical forces and usage of chlorine bleach solutions to aid in removal and sanitization of microorganisms attached on surfaces of fresh produce during washing processes. Frequent outbreaks of foodborne diseases from ready-to-eat produce indicate insufficient sanitization of the washing processes. Herein, we present a scalable methodology for creating antimicrobial and chlorine rechargeable hydrogel beads using an in situ formed network of polyacrylamide and natural polysaccharide alginate through an emulsion polymerization. The resulting hydrogel beads exhibited robust mechanical strength, rechargeable chlorination capability, rapid up to 99.99% bacterial killing efficiency, and high produce sanitizaiton efficiency, enabling the hydrogel beads as a promising additive in chlorine sanitization to effectively sanitize the produce and automatically being recharged and reused.

Technological Innovation to Reduce the Negative Environmental Impact of Industrial Wastewater

Rational use of natural resources and protection of water bodies is an actual problem of the modern world. Due to the rapidly developing industry, wastewater which contain high concentrations of suspended substances and organic pollutants is discharged to water bodies in a large volume.So design improved treatment facilities that ensure high quality of treated water is an important task.Biomembrane technology is a promising direction in water treatment, providing high efficiency of treatment at minimal cost. Compared to the traditional treatment scheme, it allows you to avoid the use of secondary settling tanks by separating the active sludge from the treated wastewater on the membranes. Due to the very small size of the membrane pores, almost complete removal of suspended substances and microorganisms is achieved. A bioreactor with an external arrangement of the membrane module provides high specific capacity.The small-bubble aeration system in the aeration tank ensures the maintenance of dissolved oxygen at a concentration of 2-3 mg / l for the correct course of the nitrification and oxidation of organic substances. The combination of biological treatment and membrane separation ensures high operational reliability and durability.This technology is used in various industries, but it is most widely used in the food and oil refining industries due to the high content of organic pollutants, which are mostly removed by this installation.The use of biomembrane technology is economically advisable for designing treatment facilities for industrial wastewater treatment from organic pollutants.