scholarly journals PIV Analysis of Cavitating Flow Behind Square Multi-Orifice Plates

10.29007/fhdg ◽  
2018 ◽  
Author(s):  
Zhiyong Dong ◽  
Wenqian Zhao
Keyword(s):  
Conventional Technique ◽  
Disinfection Byproducts ◽  
Cavitating Flow ◽  
Water Disinfection ◽  
Hydrodynamic Cavitation ◽  
Pathogenic Microorganisms ◽  
Turbulence Structures ◽  
Image Velocimetry ◽  
Piv Analysis ◽  
Mutagenic Effects

Currently, in water supply engineering, the conventional technique of disinfection by chlorination is used to kill pathogenic microorganisms in raw water. However, chlorine reacts with organic compounds in water and generates disinfection byproducts (DBPs) such as trihalomethanes (THMs), haloacetic acids (HAAs) etc. These byproducts are of carcinogenic, teratogenic and mutagenic effects, which seriously threaten human health. Hydrodynamic cavitation is a novel technique of drinking water disinfection without DBPs. Turbulence structures of cavitating flow were observed by the Particle Image Velocimetry (PIV) technique in a self-developed hydrodynamic cavitation device due to square multi- orifice plates, including effects of orifice number and orifice layout on velocity distribution, turbulence intensity and Reynolds stress, which aimed at uncovering mechanism of killing pathogenic microorganisms by hydrodynamic cavitation.

DISINFEKSI UNTUK PROSES PENGOLAHAN AIR MINUM

2018 ◽  
Vol 3 (1) ◽  
Author(s):  
Nusa Idaman Said
Keyword(s):  
Drinking Water ◽  
Water Purification ◽  
Distribution System ◽  
Residual Effect ◽  
Drinking Water Treatment ◽  
Disinfection Byproducts ◽  
Water Disinfection ◽  
Pathogenic Microorganisms ◽  
Microbiological Contamination ◽  
Disinfection Process

Water disinfection means the removal, deactivation or killing of pathogenic microorganisms. Microorganisms are destroyed or deactivated, resulting in termination of growth and reproduction. When microorganisms are not removed from drinking water, drinking water usage will cause people to fall ill. Chemical inactivation of microbiological contamination in natural or untreated water is usually one of the final steps to reduce pathogenic microorganisms in drinking water. Combinations of water purification steps (oxidation, coagulation, settling, disinfection, and filtration) cause (drinking) water to be safe after production. As an extra measure many countries apply a second disinfection step at the end of the water purification process, in order to protect the water from microbiological contamination in the water distribution system. Usually one uses a different kind of disinfectant from the one earlier in the process, during this disinfection process. The secondary disinfection makes sure that bacteria will not multiply in the water during distribution. This paper describes several technique of disinfection process for drinking water treatment. Disinfection can be attained by means of physical or chemical disinfectants. The agents also remove organic contaminants from water, which serve as nutrients or shelters for microorganisms. Disinfectants should not only kill microorganisms. Disinfectants must also have a residual effect, which means that they remain active in the water after disinfection. For chemical disinfection of water the following disinfectants can be used such as Chlorine (Cl2),  Hypo chlorite (OCl-), Chloramines, Chlorine dioxide (ClO2), Ozone (O3), Hydrogen peroxide etch. For physical disinfection of water the following disinfectants can be used is Ultraviolet light (UV). Every technique has its specific advantages and and disadvantages its own application area sucs as environmentally friendly, disinfection byproducts, effectivity, investment, operational costs etc. Kata Kunci : Disinfeksi, bakteria, virus, air minum, khlor, hip khlorit, khloramine, khlor dioksida, ozon, UV.

scholarly journals Experimental Study of Pathogenic Microorganisms Inactivated by Venturi-Type Hydrodynamic Cavitation with Different Throat Lengths

2018 ◽  
Vol 4 (3) ◽  
pp. 209 ◽  
Author(s):  
Zhiyong Dong ◽  
Zhaoyu Qin
Keyword(s):  
Flow Velocity ◽  
Disinfection Byproducts ◽  
Cavitation Number ◽  
Radius Ratio ◽  
Hydrodynamic Cavitation ◽  
Colony Count ◽  
Bubble Collapse ◽  
Pathogenic Microorganisms ◽  
Raw Water ◽  
Killing Rate

Based on self-developed Venturi-type hydrodynamic cavitation device with different throat length-radius ratios L/R in Hydraulics Laboratory at Zhejiang University of Technology in China, 4 throat length-radius ratios L/R=10, 30, 60 and 100, and 4 raw water percentages V0/V=25%, 50%, 75%, and 100% were considered, Escherichia coli and total colony count were selected for indicator bacteria, effects of throat length-radius ratio, throat velocity, cavitation time, raw water percentage and cavitation number on inactivating pathogenic microorganism in raw water by hydrodynamic cavitation were experimentally studied. The results showed cavitation damage of cells of pathogenic microorganisms occurred by microjets and shock waves due to cavitation bubble collapse. The lower the flow cavitation number, the higher the killing rate of E. coli and total colony count. When flow velocity was lower or raw water percentage was higher, killing rate gradually increased with increase in throat length-radius ratio; when flow velocity was higher or raw water percentage was lower, killing rate was almost independent of throat length-radius ratio. Inactivated effect of pathogenic microorganisms can be further enhanced by increasing throat velocity or prolonging cavitation time. Hydrodynamic cavitation is a novel disinfection technique for drinking water without disinfection byproducts (DBPs) and no need to add disinfectant.

Excystation ofCryptosporidium parvumat temperatures that are reached during solar water disinfection

Parasitology ◽  
2009 ◽  
Vol 136 (4) ◽  
pp. 393-399 ◽  
Author(s):  
H. GÓMEZ-COUSO ◽  
M. FONTÁN-SAINZ ◽  
J. FERNÁNDEZ-ALONSO ◽  
E. ARES-MAZÁS
Keyword(s):  
Solar Radiation ◽  
Cryptosporidium Parvum ◽  
Gradual Increase ◽  
Water Disinfection ◽  
Waterborne Diseases ◽  
Pathogenic Microorganisms ◽  
Simple Method ◽  
Solar Water ◽  
Solar Water Disinfection ◽  
Notable Increase

SUMMARYSpecies belonging to the generaCryptosporidiumare recognized as waterborne pathogens. Solar water disinfection (SODIS) is a simple method that involves the use of solar radiation to destroy pathogenic microorganisms that cause waterborne diseases. A notable increase in water temperature and the existence of a large number of empty or partially excysted (i.e. unviable) oocysts have been observed in previous SODIS studies with water experimentally contaminated withCryptosporidium parvumoocysts under field conditions. The aim of the present study was to evaluate the effect of the temperatures that can be reached during exposure of water samples to natural sunlight (37–50°C), on the excystation ofC. parvumin the absence of other stimuli. In samples exposed to 40–48°C, a gradual increase in the percentage of excystation was observed as the time of exposure increased and a maximum of 53·81% of excystation was obtained on exposure of the water to a temperature of 46°C for 12 h (versus8·80% initial isolate). Under such conditions, the oocyst infectivity evaluated in a neonatal murine model decreased statistically with respect to the initial isolate (19·38%versus100%). The results demonstrate the important effect of the temperature on the excystation ofC. parvumand therefore on its viability and infectivity.

Assessment of Tandem Venturi on Enhancement of Cavitational Chemical Reaction

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Hoseyn Sayyaadi
Keyword(s):  
Chemical Reaction ◽  
Oxidation Process ◽  
Flow Characteristics ◽  
Chemical Oxidation ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Hydrodynamic Cavitation ◽  
Operating Pressure ◽  
Local Pressures ◽  
Second Category

The collapsing phenomenon of cavitation bubbles generates extremely high local pressures and temperatures that can be utilized for the chemical oxidation process. This process is carried out in cavitation reactors. A Venturi tube is one of the most common forms of hydrodynamic cavitation reactors, which is suitable for industrial scale applications. In this work, the hydraulic performance and efficiency in chemical reaction of a new form of hydrodynamic cavitation reactors, which is called “tandem Venturi,” were studied and compared with the conventional type of the single Venturi. The tandem Venturi is used for enhancement of the chemical reaction of hydrodynamic cavitating flow. The reaction enhancement is useful especially for the reaction of aqueous solutions not containing volatile organic compounds (VOCs). The operating pressure, inlet pressure, flow rate, and consequently the cavitation number were controlled and systematically varied for both single and tandem Venturis. Moreover, a specified amount of H2O2 was injected into the flow as required. The effects of operating pressure and the cavitation number on cavitating flow characteristics for single and tandem Venturis were experimentally observed and the results were compared. In addition, the performance of the tandem-Venturi reactor for degradation of non-VOC contaminants (2-chlorophenol) was studied. Its performance was compared with the performance of a conventional Venturi reactor. Two different categories were conducted for the experiments. In the first category, the effect of the net cavitating flow on degradation of non-VOC for the single and tandem Venturis was compared. In the second category, the effect of H2O2 injection into the cavitating flow on degradation of non-VOC (“cavitation-oxidation” process) was studied. The performance of the single and tandem Venturis for the cavitation-oxidation process was compared. Further investigation was performed to assess the advantage of utilizing the tandem Venturi from the viewpoint of efficiency of the oxidation process. The results of the energy efficiency were compared with the corresponding efficiency of the single Venturi. Finally, the relationship between the main parameters of cavitation reaction flow with the chemical performance was discussed.

scholarly journals Association between exposure to drinking water disinfection byproducts and adverse pregnancy outcomes in South Africa

2020 ◽  
Author(s):  
Funanani Mashau ◽  
Esper Jacobeth Ncube ◽  
Kuku Voyi
Keyword(s):  
Drinking Water ◽  
Pregnancy Outcomes ◽  
Premature Birth ◽  
Disinfection Byproducts ◽  
Maternal Exposure ◽  
Adverse Pregnancy Outcomes ◽  
Water Disinfection ◽  
Regulatory Data ◽  
Adverse Pregnancy ◽  
The Individual

Abstract Currently, there is contradictory evidence for the risk of adverse pregnancy outcomes associated with maternal exposure to disinfection byproducts (DBPs). We examine the association between maternal exposure to trihalomethanes (THMs) in drinking water and adverse pregnancy outcomes, including premature birth, low birth weight (LBW) and small for gestational age (SGA). In total, 1,167 women older than 18 years were enrolled at public antenatal venues in two geographical districts. For each district, we measured the levels of residential drinking water DBPs (measured in THMs) through regulatory data and routine water sampling. We estimated the individual uptake of water of each woman by combining individual water use and uptake factors. Increased daily internal dose of total THMs during the third trimester of pregnancy significantly increased the risk of delivering premature infants (AOR 3.13, 95% CI 1.36–7.17). The risk of premature birth was also positiviely associated with exposure to total THMs during the whole pregnancy (AOR 2.89, 95% CI 1.25–6.68). The risk of delivering an SGA and LBW infant was not associated with maternal exposure to THMs. Our findings suggest that exposure to THMs is associated with certain negative pregnancy outcomes. The levels of THMs in water should be routinely monitored.

scholarly journals Novel analysis for large strains based on particle image velocimetry

2017 ◽  
Vol 54 (7) ◽  
pp. 933-944 ◽  
Author(s):  
Núria M. Pinyol ◽  
Mauricio Alvarado
Keyword(s):  
Particle Image Velocimetry ◽  
Slope Failure ◽  
Particle Image ◽  
Large Strains ◽  
Software Packages ◽  
Piv Technique ◽  
Standard Procedures ◽  
Image Velocimetry ◽  
Sandy Slope ◽  
Piv Analysis

Over the last few decades, the particle image velocimetry (PIV) technique has become an interesting tool used to measure displacements in the field of experimental mechanics. This paper presents a procedure to interpret PIV displacements, measured following an Eulerian scheme, with the purpose of providing accumulated displacements, velocities, accelerations, and strains on points representing physical particles. Strains are computed as the gradient of displacements. When compared with other standard procedures already published, the presented methodology is especially well suited to interpret large strains. The basis of the procedure is to map displacement increments measured through PIV analysis on the subset (or patch) centres into numerical particles that are defined as portions of the moving masses whose deformation is analyzed. The implementation of the method is explained in detail, highlighting its simplicity. The procedure can be used as a post-processor of currently available PIV software packages. The methodology is first applied to synthetic cases of rectangular samples in which known displacements are imposed and also to a sandy slope failure experiment involving large displacements. The method reproduces satisfactorily the recorded images.

scholarly journals Degradation of Aqueous Polycyclic Musk Tonalide by Ultraviolet-Activated Free Chlorine

Processes ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 95 ◽  
Author(s):  
Lili Wang ◽  
Xiaowei Liu
Keyword(s):  
Disinfection Byproducts ◽  
Free Chlorine ◽  
Water Disinfection ◽  
Side Chain ◽  
Product Analysis ◽  
Direct Photolysis ◽  
Reaction Rate Constants ◽  
Water Matrix ◽  
First Order Kinetics ◽  
Drinking Water Disinfection

Chlorine-incorporating ultraviolet (UV) provides a multiple barrier for drinking water disinfection. Meanwhile, post-UV employment can promote the degradation of micropollutants by radical production from chlorine residual photolysis. This work studied the degradation of one such chemical, tonalide (AHTN), by low-pressure UV-activated free chlorine (FC) under typical UV disinfection dosage of <200 mJ·cm−2 and water matrix of filtered tank effluent. AHTN was rapidly degraded by UV/FC in accordance with pseudo-first-order kinetics. The reaction rate constants of AHTN with reactive chlorine species and hydroxyl radical (HO•) were estimated. Mechanistic exploration evidenced that under UV/FC, AHTN degradation was attributable to direct photolysis, ClO•, and HO•. The carbonyl side chain of AHTN served as an important attack site for radicals. Water matrices, such as natural organic matter (NOM), HCO3−, Cu2+, PO43−, and Fe2+, showed noticeable influence on the UV/FC process with an order of NOM > HCO3− >Cu2+ > PO43− > Fe2+. Reaction product analysis showed ignorable formation of chlorinated intermediates and disinfection byproducts.

Experimental and Numerical Study of Hydrodynamic Cavitation of Orifice Plates with Multiple Triangular Holes

2012 ◽  
Vol 256-259 ◽  
pp. 2519-2522 ◽  
Author(s):  
Zhi Yong Dong ◽  
Qi Qi Chen ◽  
Yong Gang Yang ◽  
Bin Shi
Keyword(s):  
Velocity Profile ◽  
High Speed ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Orifice Plate ◽  
Hydrodynamic Cavitation ◽  
High Speed Photography ◽  
Hydraulic Characteristics ◽  
Image Velocimetry

Hydraulic characteristics of orifice plates with multiple triangular holes in hydrodynamic cavitation reactor were experimentally investigated by use of three dimensional particle image velocimetry (PIV), high speed photography, electronic multi-pressure scanivalve and pressure data acquisition system, and numerically simulated by CFD software Flow 3D in this paper. Effects of number, arrangement and ratio of holes on hydraulic characteristics of the orifice plates were considered. Effects of arrangement and ratio of holes and flow velocity ahead of plate on cavitation number and velocity profile were compared. Distribution of turbulent kinetic energy and similarity of velocity profile were analyzed. And characteristics of cavitating flow downstream of the orifice plate were photographically observed by high speed camera. Also, a comparison with flow characteristics of orifice plate with hybrid holes (circle, square and triangle) was made.

Sign in / Sign up

Export Citation Format

Share Document