Disinfection of Natural Water by Solar Photocatalysis Using Immobilized TiO2 Devices: Efficiency in Eliminating Indicator Bacteria and Operating Life of the System

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Asunción Acevedo ◽  
Edward A. Carpio ◽  
Juan Rodríguez ◽  
Manuel A. Manzano
Keyword(s):  
Calcium Carbonate ◽  
Natural Water ◽  
Sol Gel ◽  
Longitudinal Axis ◽  
Alternative Methods ◽  
Design Parameters ◽  
Human Consumption ◽  
Operating Life ◽  
Solar Simulator ◽  
E Coli

Natural water has been disinfected using TiO2 as the fixed catalyst incorporated in a homemade photoreactor, in which the dimensions and the design parameters are representative of devices that are currently employed at larger scale. The catalyst was immobilized on the external surface of a cylinder of frosted glass situated in the longitudinal axis of a tubular glass reactor. Two alternative methods of immobilizing the catalyst on glass were studied: in the first, a commercial titanium oxide powder (Aeroxide® TiO2 P25) was mounted on a polymeric support; and in the second, it was applied by sol-gel deposition. Illumination was effected by installing the glass reactor in the irradiation chamber of a solar simulator. Under laboratory conditions, groundwater contaminated with cultured and wild bacteria was treated photocatalytically, and the influence of the photolysis, the pumping, and the catalysts was studied. The results obtained have demonstrated that the catalyst immobilized in the interior of the photoreactor presents similar results, in the disinfection of E. coli, as 0.5 g/l of TiO2 P25; and that, in 1.5 h approximately of simulated solar illumination (167 kWUVA s/m2) on the sol-gel deposit of TiO2, it is possible to eliminate 100% of the bacteria covered by international regulations in respect of water for human consumption. With regard to the aging assay of the system, it was observed at 250 h of operation a reduction in the effectiveness of the disinfection process. At 0 and 250 h of operation, the percentages of elimination of E. coli after 50 min of illumination were 100% and 99.5%, respectively. This reduction in the effectiveness of the process was due to the formation of a film of calcium carbonate adhering to the internal glass wall of the photoreactor, which is in contact with the liquid being treated, and to the presence of calcium carbonate precipitates on catalyst surface.

scholarly journals The effect of activation of the lactoperoxidase system and souring on certain potential human pathogens in cows' milk

1997 ◽  
Vol 68 (4) ◽  
Author(s):  
J.G.K. Kangumba ◽  
E.H. Venter ◽  
J.A.W. Coetzer
Keyword(s):  
Rural Communities ◽  
Alternative Methods ◽  
Human Consumption ◽  
Socioeconomic Conditions ◽  
Human Pathogens ◽  
Pathogenic Potential ◽  
E Coli ◽  
Lactoperoxidase System ◽  
Potential Alternative ◽  
System Activation

Conventional methods of ensuring the safety and soundness of cows' milk for human consumption, such as pasteurisation, are not always practical in poor socioeconomic conditions or in rural communities that lack modern amenities. Activation of lactoperoxidase (LP) system and souring of milk were investigated as potential alternative methods to sustain the safety of milk by inhibiting certain microorganisms with known pathogenic potential. The activation of the LP-system inhibited the growth of Staphylococcus aureus and Escherichia coli by the order of 2 log values. The inhibition of Brucella abortus was negligible. The replication of Coxiella burnetti in milk was not disturbed even after 17 h of LP-system activation at 20 oC, but the outcome of the LP-system treatment on Mycobacterium bovis could not be determined as the conventional culturing technique used to grow this organism did not allow full recovery. Souring inhibited the growth of S. aureus and E. coli also by the order of 2 log values. From the results obtained in this investigation are concluded that the activation of the LP-system and souring can be used to inhibit the growth of S. aureus and E. coli in cows' milk, thereby increasing its safety.

Evaluation of Coli-ID and MUG Plus media for recovering Escherichia coli and other coliform bacteria from groundwater samples

2001 ◽  
Vol 43 (12) ◽  
pp. 213-216 ◽  
Author(s):  
R. A. Sueiro ◽  
M. Araujo ◽  
C. J. Santos ◽  
M. J. Gómes ◽  
M. J. Garrido
Keyword(s):  
Escherichia Coli ◽  
Variance Analysis ◽  
Alternative Methods ◽  
Coliform Bacteria ◽  
Human Consumption ◽  
Recovery Efficiency ◽  
E Coli ◽  
Reference Methods ◽  
Groundwater Samples ◽  
Reference Medium

Several chromogenic media for detecting coliform bacteria in water are commercially available including Coli ID medium (ID) (bioMérieux) and MUG Plus cefsulodin agar (MP) (Laboratorios Microkit, S.L.). Since little is known about the performance of these media, we have evaluated their usefulness for recovering Escherichia coli and other coliform organisms in groundwaters used for direct human consumption. Variance analysis of obtained data showed that no statistically significant differences in counts of E. coli and other coliforms on ID and MP media compared with reference methods. However, the evaluation of sensitivity and recovery efficiency of both media showed that the two chromogenic media were more sensitive and significantly more efficient (P = ļ0.05) than reference medium for detecting coliforms in groundwater. However, the identification of 400 typical and atypical colonies isolated from ID and MP media demonstrated a higher specificity when using ID for coliforms and E. coli. In summary, the two chromogenic media evaluated could be used as alternative methods to reference media for detecting and recovering coliform bacteria in groundwater samples. MP agar was more sensitive and efficient than ID agar whereas the latter was more specific and selective.

PENGARUH KONSENTRASI KITOSAN PADA SINTESIS NANOPARTIKEL TIO2 UNTUK APLIKASI PADA DYESENSITIZED SOLAR CELL (DSSC)

2013 ◽  
Vol 3 (2) ◽  
pp. 77
Author(s):  
Maya Komalasari ◽  
Teuku Fawzul Akbardan ◽  
Bambang Sunendar
Keyword(s):  
Solar Cell ◽  
Sol Gel ◽  
Dye Sensitized Solar Cell ◽  
Solar Simulator ◽  
Dye Sensitized

Pada penelitian ini dilakukan sintesis nanopartikel TiO2 menggunakan metode sol-gel dengan pelarut air. Pada proses sintesis ditambahkan kitosan dengan konsentrasi 0; 2,5; 5; dan 10% v/v. TiO2hasil sintesis kemudian dikarakterisasi dengan menggunakan SEM, XRD, dan BET  untuk mengetahui morfologi,  struktur kristal, dan karakteristik pori. Selain itu keempat variasi TiO2diaplikasikan sebagai foto elektroda DSSC. Karakterisasi DSSC dilakukan dengan menggunakan solar simulator AM 1,5 untuk mengetahui karakteristik I-V DSSC. Hasil karakterisasi menunjukkan penambahan kitosan pada konsentrasi rendah (2,5% v/v) mengurangi fasa anatase pada kristal  TiO2dan cenderung memperbesar ukuran kristalit. Penambahan kitosan melebihi 5% meningkatkan fasa anatase dan memperkecil ukuran kristalit. Konsentrasi kitosan 2,5% memperkecil luas permukaan spesifik partikel dan volume total pori. Peningkatan konsentrasi kitosan memberi hasil sebaliknya. Performa DSSC terbaik didapat pada TiO2 dengan konsentrasi kitosan 2,5% saat sintesis, dengan Voc = 0,58 V, Jsc = 0,74 mA/cm , dan η = 0,51%.Kata kunci: titanium dioksida, Dye Sensitized Solar Cell, kitosan

scholarly journals Comparison of the ColiPlate™ Kit with Two Common E. coli Enumeration Methods for Water

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1804
Author(s):  
Cassi J. Gibson ◽  
Abraham K. Maritim ◽  
Jason W. Marion
Keyword(s):  
High Risk ◽  
Natural Water ◽  
Membrane Filtration ◽  
Fecal Contamination ◽  
Reference Method ◽  
World Health ◽  
Risk Levels ◽  
E Coli ◽  
Field Samples ◽  
Very High

Quantitatively assessing fecal indicator bacteria in drinking water from limited resource settings (e.g., disasters, remote areas) can inform public health strategies for reducing waterborne illnesses. This study aimed to compare two common approaches for quantifying Escherichia coli (E. coli) density in natural water versus the ColiPlate™ kit approach. For comparing methods, 41 field samples from natural water sources in Kentucky (USA) were collected. E. coli densities were then determined by (1) membrane filtration in conjunction with modified membrane-thermotolerant E. coli (mTEC) agar, (2) Idexx Quanti-Tray® 2000 with the Colilert® substrate, and (3) the Bluewater Biosciences ColiPlate kit. Significant correlations were observed between E. coli density data for all three methods (p < 0.001). Paired t-test results showed no difference in E. coli densities determined by all the methods (p > 0.05). Upon assigning modified mTEC as the reference method for determining the World Health Organization-assigned “very high-risk” levels of fecal contamination (> 100 E. coli CFU/100 mL), both ColiPlate and Colilert exhibited excellent discrimination for screening very high-risk levels according to the area under the receiver operating characteristic curve (~89%). These data suggest ColiPlate continues to be an effective monitoring tool for quantifying E. coli density and characterizing fecal contamination risks from water.

The use of antibiotic resistance profiling as a means of tracing sources of fecal contamination in source waters

2010 ◽  
Vol 10 (2) ◽  
pp. 209-215
Author(s):  
M. S. Mthembu ◽  
P. T. Biyela ◽  
T. G. Djarova ◽  
A. K. Basson
Keyword(s):  
Antibiotic Resistance ◽  
Municipal Wastewater ◽  
Fecal Contamination ◽  
Source Tracking ◽  
Human Consumption ◽  
Biochemical Tests ◽  
Isolation And Identification ◽  
E Coli ◽  
Intestinal Pathogens ◽  
Source Waters

Fecal contamination of source waters and its associated intestinal pathogens continues to pose risks to public health although the extent and effect of microbial contamination of source waters gets very little attention in designing treatment plants in most developing countries. Coliform counts give an indication of the overall bacterial contamination of water and thus its safety for human consumption. However, their presence fails to provide information about the source of fecal contamination which is vital to managing fecal contamination problems in surface waters. This study explored the use of multiple antibiotic resistance (MAR) indexing as means of differentiating E. coli isolates from different sources. A total of 322 E. coli isolates were obtained from municipal wastewater and from fecal samples from domestic and wild animals. Conventional culture methods and standard chemical and biochemical tests were used for isolation and identification of E. coli. Isolates were assayed against 10 antibiotics using the micro-dilution technique. The results obtained generated antibiotic resistance profiles which were used to statistically group the isolates into different subsets. Correct source classification was obtained for 60% of human-derived and 95% non-human-derived E. coli respectively. These results indicate the validity of the usefulness of MAR indexing as a method of bacterial source tracking.

Development and Mechanical Characterization of a Collagen/Hydroxyapatite Bilayered Scaffold for Ostechondral Defect Replacement

2011 ◽  
Vol 493-494 ◽  
pp. 890-895 ◽  
Author(s):  
Francesca Gervaso ◽  
Francesca Scalera ◽  
Sanosh Kunjalukkal Padmanabhan ◽  
Antonio Licciulli ◽  
Daniela Deponti ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Sol Gel ◽  
Three Dimensional ◽  
Collagen Scaffold ◽  
Mechanical Analysis ◽  
Design Parameters ◽  
Compression Tests ◽  
Templating Method ◽  
Organic Part ◽  
Hydroxyapatite Scaffold

In this work a novel three-dimensional ostechondral substitute is proposed that is made of an inorganic/organic hybrid material, namely collagen/hydroxyapatite. The two components of the substitute have been characterized separately. The inorganic part, a hydroxyapatite scaffold, was fabricated by a polymer sponge templating method using a reactive sub-micron powder synthesized in our laboratory by hydroxide precipitation sol-gel route. The organic part, a collagen scaffold, was fabricated by a freeze-dying technique varying design parameters. Both the parts were analysed by scanning electron microscopy and their mechanical properties assessed by compression tests. The hydroxyapatite scaffold showed a high and highly interconnected porosity and a mechanical strength equal to 0.55 MPa, higher than those reported in literature. The collagen scaffolds were seeded by chondrocytes, processed for histology analysis and tested in compression. The biological tests proved the ability of the scaffolds to be positively populated by chondrocytes and the mechanical analysis showed that the mechanical strength of the scaffolds significantly increased after 3 weeks of culture.

scholarly journals Studies on the Preservation of Raw Cow’s Milk by Chemical Method

1970 ◽  
Vol 42 (3) ◽  
pp. 317-326 ◽  
Author(s):  
F Rokhsana ◽  
UK Das ◽  
R Yeasmin ◽  
A Nahar ◽  
S Parveen
Keyword(s):  
Hydrogen Peroxide ◽  
Chemical Method ◽  
Room Temperature ◽  
Storage Period ◽  
Total Coliform ◽  
Human Consumption ◽  
Milk Products ◽  
E Coli ◽  
Keeping Quality ◽  
Control Milk

Studies carried out to develop a technique for the preservation of cow's milk in raw condition using hydrogen peroxide (H2O2) as a preservative. Fresh cow’s milk was collected and experiments were conducted by four treatments in order to achieve the optimum condition of storage. The treatments were with various concentration of H2O2 starting from 0.05 %, 0.1 %, 0.2 %, 0.3 %, 0.4 %, & 0.5 %. Treated milk with 0.05 % concentration of H2O2 had storage period of 20 days compared to that of the control one (5 days only) in refrigerated temperature (±8°C). On the other hand hydrogen peroxide treated milk (0.05 %) had a storage period of 8 hours at room temperature (±28°C). Results also showed that the higher concentration of H2O2 had no effect on storage period than that of control. Milk products like kheer and halawa prepared by treated milk and stored for 20 days showed almost nil growth of total coliform and E. coli which means that food products prepared from hydrogen peroxide treated milk is safe for human consumption. Key words: Raw, Storage, Hydrogen peroxide, Preservative, keeping quality, Pasteurization, deteriorated, MPN. Bangladesh J. Sci. Ind. Res. 42(3), 317-326, 2007

scholarly journals Effect of the suspension of Ag-incorporated TiO2 nanoparticles (Ag-TiO2 NPs) on certain growth, physiology and phytotoxicity parameters in spinach seedlings

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244511
Author(s):  
Fernando Gordillo-Delgado ◽  
Jakeline Zuluaga-Acosta ◽  
Gonzalo Restrepo-Guerrero
Keyword(s):  
Particle Size ◽  
Titanium Dioxide Nanoparticles ◽  
Germination Rate ◽  
Sol Gel ◽  
Control Group ◽  
Human Consumption ◽  
X Ray Diffraction ◽  
X Ray ◽  
Growth Physiology ◽  
Powder Samples

In this work, the effect of the inoculation of silver-incorporated titanium dioxide nanoparticles (Ag-TiO2 NPs) in spinach seeds was evaluated on certain growth, physiology and phytotoxicity parameters of the plants. This is an important crop for human consumption with high nutritional value due to their low calorie and fat content, providing various vitamins and minerals, especially iron. These NPs were obtained by means of the sol-gel method and heat treatment; the resulting powder material was characterized using X-ray diffraction and scanning electron microscopy and the influence of these NPs on plants was measured by estimating the germination rate, monitoring morphological parameters and evaluating phytotoxicity. The photosynthetic activity of the spinach plants was estimated through the quantification of the Ratio of Oxygen Evolution (ROE) by the photoacoustic technique. Samples of TiO2 powder with particle size between 9 and 43 nm were used to quantify the germination rate, which served to determine a narrower size range between 7 and 26 nm in the experiments with Ag-TiO2 NPs; the presence of Ag in TiO2 powder samples was confirmed by energy-dispersive X-ray spectroscopy. The analysis of variance showed that the dependent variable (plant growth) could be affected by the evaluated factors (concentration and size) with significant differences. The statistical trend indicated that the application of the Ag-TiO2 NPs suspension of lowest concentration and smallest particle size could be a promoting agent of the growth and development of these plants. The inoculation with NPs of 8.3 nm size and lowest concentration was related to the highest average ROE value, 24.6 ± 0.2%, while the control group was 20.2 ± 0.2%. The positive effect of the Ag-TiO2 NPs treatment could be associated to the generation of reactive oxygen species, antimicrobial activity, increased biochemical attributes, enzymatic activity or improvements in water absorption.

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