Kinetics of bacteria inactivation employing UV radiation under clear water conditions

2006 ◽  
Vol 121 (2-3) ◽  
pp. 135-145 ◽  
Author(s):  
M LABAS ◽  
R BRANDI ◽  
C MARTIN ◽  
A CASSANO
Keyword(s):  
Uv Radiation ◽  
Clear Water ◽  
Bacteria Inactivation ◽  
Water Conditions ◽  
Kinetics Of

Water decolorization using UV radiation and hydrogen peroxide: A kinetic study

2001 ◽  
Vol 44 (5) ◽  
pp. 53-60 ◽  
Author(s):  
C.A. Martín ◽  
O.M. Alfano ◽  
A.E. Cassano
Keyword(s):  
Hydrogen Peroxide ◽  
Uv Radiation ◽  
Absorption Rate ◽  
Fulvic Acids ◽  
Photon Absorption ◽  
Contaminant Concentration ◽  
Organic Substances ◽  
Mechanistic Approach ◽  
Natural Contamination ◽  
Kinetics Of

Sometimes, provision of water for domiciliary consumption faces the problem of natural contamination originated by the presence of organic substances such as humic or fulvic acids. Very often, after conventional sanitary treatments this water exhibits a persistent yellowish coloration that affects its use. Moreover, these substances may act as precursors of tri-halomethanes formation during pre-desinfection with chlorine. This paper presents, with a simplified mechanistic approach, the intrinsic reaction kinetics of natural water decolorization employing UV radiation and hydrogen peroxide. The main variables for the model are: contaminant concentration expressed as TOC, hydrogen peroxide concentration and the photon absorption rate.

Riprap Performance at Bridge Piers Under Mobile-Bed Conditions

1998 ◽  
Vol 1647 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Carlos Toro-Escobar ◽  
Richard Voigt ◽  
Bruce Melville ◽  
Meng Chiew ◽  
Gary Parker
Keyword(s):  
Experimental Tests ◽  
Bridge Piers ◽  
Design Criteria ◽  
Research Groups ◽  
Clear Water ◽  
Pier Scour ◽  
Mobile Bed ◽  
Water Conditions ◽  
Improved Design ◽  
Flood Flow

Design criteria for riprap at bridge piers in rivers is based on the specification of a size, gradation, and cover that does not fail under an appropriately chosen flood flow. Experimental tests of riprap performance at bridge piers to date have relied on a configuration for which the ambient bed is not mobilized, that is, clear-water conditions. In the field, however, riprap is, as a rule, subjected to mobile-bed conditions during floods. Recent experiments by three cooperating research groups (University of Auckland, Nanyang University, and St. Anthony Falls Laboratory) indicate a heretofore unrecognized mechanism for riprap failure under mobile-bed conditions. When the flow is in the dune regime, the passage of successive dunes causes riprap that is never directly entrained by the flow to sink and disperse. Pier scour is realized as a consequence of these processes. In some cases, the depth of scour realized is not significantly less than that which would occur without riprap. When the riprap is fully underlain by a geotextile, edge effects can cause local removal of riprap, upturning of the geotextile, and general failure. When the riprap is underlain by a partial geotextile (i.e., one that covers an area less than the riprap), edge scour causes local sinking that anchors the geotextile. The sinking and dispersion of the rest of the riprap are greatly limited, and the riprap fails only when flow velocities are sufficient for direct entrainment. The experiments suggest improved design criteria for the installation of riprap in the field.

Molecular analysis of enhanced replication of UV-damaged simian virus 40 DNA in UV-treated mammalian cells

1988 ◽  
Vol 8 (6) ◽  
pp. 2428-2434
Author(s):  
J M Treger ◽  
J Hauser ◽  
K Dixon
Keyword(s):  
Uv Radiation ◽  
Uv Irradiation ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Viral Dna ◽  
Repair Capacity ◽  
Pyrimidine Dimers ◽  
Infected Cells ◽  
Replicative Intermediates ◽  
Kinetics Of

Irradiation of simian virus 40 (SV40)-infected cells with low fluences of UV light (20 to 60 J/m2, inducing one to three pyrimidine dimers per SV40 genome) causes a dramatic inhibition of viral DNA replication. However, treatment of cells with UV radiation (20 J/m2) before infection with SV40 virus enhances the replication of UV-damaged viral DNA. To investigate the mechanism of this enhancement of replication, we analyzed the kinetics of synthesis and interconversion of viral replicative intermediates synthesized after UV irradiation of SV40-infected cells that had been pretreated with UV radiation. This enhancement did not appear to be due to an expansion of the size of the pool of replicative intermediates after irradiation of pretreated infected cells; the kinetics of incorporation of labeled thymidine into replicative intermediates were very similar after irradiation of infected control and pretreated cells. The major products of replication of SV40 DNA after UV irradiation at the low UV fluences used here were form II molecules with single-stranded gaps (relaxed circular intermediates). There did not appear to be a change in the proportion of these molecules synthesized when cells were pretreated with UV radiation. Thus, it is unlikely that a substantial amount of DNA synthesis occurs past pyrimidine dimers without leaving gaps. This conclusion is supported by the observation that the proportion of newly synthesized SV40 form I molecules that contain pyrimidine dimers was not increased in pretreated cells. Pulse-chase experiments suggested that there is a more efficient conversion of replicative intermediates into form I molecules in pretreated cells. This could be due to more efficient gap filling in relaxed circular intermediate molecules or to the release of blocked replication forks. Alternatively, the enhanced replication observed here may be due to an increase in the excision repair capacity of the pretreated cells.

An initial assessment of bed destabilization risk past vegetation patches using instrumented particles

2021 ◽  
Author(s):  
Yi Xu ◽  
Valyrakis Manousos ◽  
Panagiotis Michalis
Keyword(s):  
Initial Assessment ◽  
Flow Structures ◽  
Clear Water ◽  
Flow Conditions ◽  
Flow Parameters ◽  
Water Conditions ◽  
The Mean ◽  
Acoustic Doppler Velocimetry ◽  
Patch Density ◽  
Vegetation Patches

<p>Instream vegetation may alter the mean and turbukent flow fields leading to destabilizing riverbed surface, under certain flow conditions. In particular, recent research on instream vegetation hydrodynamics and ecohydrogeomorphology has focused on how energetic flow structures and bulk flow parameters downstream a vegetation may result in riverbed destabilization. This study, demonstrated the application of a 20mm novel instrumented particle in recording entrainment rates downstream simulated vegetation patches of distinct densities, at various distances downstream these. A patch of 6mm acrilic cylinders is used to simulate the emergent vegetation having the same diameter (12cm) and different porosities or densities (void volume equal to 1.25%, 3.15%, 6.25%, 11.25%, and 17.25%). The flow velocity near the instrumented particle is recorded using acoustic Doppler velocimetry (ADV) with appropriate seeding, under clear water conditions. Preliminary results are presented with focus on the effect of vegetation patch density on the flow field and subsequent effects on particle entrainment rates and implications for bed surface destabilisation.</p>

scholarly journals How the Neurotoxin β-N-Methylamino-l-Alanine Accumulates in Bivalves: Distribution of the Different Accumulation Fractions among Organs

Toxins ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 61
Author(s):  
Alexandra Lepoutre ◽  
Elisabeth J. Faassen ◽  
A. J. Zweers ◽  
Miquel Lürling ◽  
Alain Geffard ◽  
...  
Keyword(s):  
Digestive Gland ◽  
Dreissena Polymorpha ◽  
Soft Tissues ◽  
Target Organ ◽  
Organ Distribution ◽  
Tandem Mass ◽  
Clear Water ◽  
Few Data ◽  
Kinetics Of ◽  
Over Time

The environmental neurotoxin β-methylamino-l-alanine (BMAA) may represent a risk for human health. BMAA accumulates in freshwater and marine organisms consumed by humans. However, few data are available about the kinetics of BMAA accumulation and detoxification in exposed organisms, as well as the organ distribution and the fractions in which BMAA is present in tissues (free, soluble bound or precipitated bound cellular fractions). Here, we exposed the bivalve mussel Dreissena polymorpha to 7.5 µg of dissolved BMAA/mussel/3 days for 21 days, followed by 21 days of depuration in clear water. At 1, 3, 8, 14 and 21 days of exposure and depuration, the hemolymph and organs (digestive gland, the gills, the mantle, the gonad and muscles/foot) were sampled. Total BMAA as well as free BMAA, soluble bound and precipitated bound BMAA were quantified by tandem mass spectrometry. Free and soluble bound BMAA spread throughout all tissues from the first day of exposure to the last day of depuration, without a specific target organ. However, precipitated bound BMAA was detected only in muscles and foot from the last day of exposure to day 8 of depuration, at a lower concentration compared to free and soluble bound BMAA. In soft tissues (digestive gland, gonad, gills, mantle and muscles/foot), BMAA mostly accumulated as a free molecule and in the soluble bound fraction, with variations occurring between the two fractions among tissues and over time. The results suggest that the assessment of bivalve contamination by BMAA may require the quantification of total BMAA in whole individuals when possible.

scholarly journals A tryptophan synchronous and normal fluorescence study on bacteria inactivation mechanism

2019 ◽  
Vol 116 (38) ◽  
pp. 18822-18826 ◽  
Author(s):  
Runze Li ◽  
Dinesh Dhankhar ◽  
Jie Chen ◽  
Thomas C. Cesario ◽  
Peter M. Rentzepis
Keyword(s):  
Fluorescence Intensity ◽  
Protein Unfolding ◽  
Uv Light ◽  
Quantum Yields ◽  
Continuous Irradiation ◽  
Minute Period ◽  
Bacteria Inactivation ◽  
Tryptophan Residues ◽  
Inactivation Mechanism ◽  
Kinetics Of

The UV photodissociation kinetics of tryptophan amino acid, Trp, attached to the membrane of bacteria, Escherichia coli and Bacillus subtilis, have been studied by means of normal and synchronous fluorescence. Our experimental data suggest that the fluorescence intensity of Trp increases during the first minute of irradiation with 250 nm to ∼ 280 nm, 7 mW/cm2 UV light, and subsequently decreases with continuous irradiation. During this short, less than a minute, period of time, 70% of the 107 cell per milliliter bacteria are inactivated. This increase in fluorescence intensity is not observed when tryptophan is in the free state, namely, not attached to a protein, but dissolved in water or saline solution. This increase in fluorescence is attributed to the additional fluorescence of tryptophan molecules formed by protein unfolding, the breakage of the bond that attaches Trp to the bacterial protein membrane, or possibly caused by the irradiation of 2 types of tryptophan residues that photolyze with different quantum yields.

Conception et performance d'un champ d'épandage de grandes dimensions

1988 ◽  
Vol 15 (2) ◽  
pp. 216-222 ◽  
Author(s):  
Robert P. Chapuis
Keyword(s):  
Service Life ◽  
Ground Water ◽  
Infiltration Rate ◽  
Full Scale ◽  
Full Scale Test ◽  
Clear Water ◽  
Good Design ◽  
Water Conditions ◽  
Evaporation Losses ◽  
Scale Test

A large disposal field (31 × 69 m) was designed in agreement with legal recommendations. A full scale test with clear water revealed that the field exfiltration rate was much lower than anticipated. This paper describes the design, the instrumentation performed with eleven piezometers, the ground-water conditions as modified by the disposal field, how the true exfiltration rates have been determined after due consideration of natural precipitations and evaporation losses, and also the method used to improve the performance. The value of the infiltration rate into the soil, initially established by percolation tests, was confirmed by permeability tests performed in the piezometers. However, the true exfiltration rate of this disposal field was only 8% of the rate predicted by the conventional, legal design. It is established that this exfiltration rate cannot be derived by simple transposition of the results of percolation tests as presently done by by-laws. Alternatively, more rigorous methods are described. For a good design, it is necessary to perform hydrogeologic studies much more detailed than those presently required by by-laws. Finally, for improving the design and service life of such disposal fields, several suggestions are made to avoid water mounds and to reduce the risk of clogging.

KINETICS OF ATRAZINE OXIDATION BY UV RADIATION AND OXALATE ASSISTED H2O2/UV PROCESSES

2006 ◽  
Vol 11 (1) ◽  
pp. 28-32
Author(s):  
Hyun-Jin Choi ◽  
Jong-Duck Choi ◽  
Hyun-Kab Kim ◽  
Tae-Jin Lee
Keyword(s):  
Uv Radiation ◽  
Kinetics Of
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