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.

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.

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 Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

2017 ◽  
Vol 473 (2199) ◽  
pp. 20160345 ◽  
Author(s):  
A. Ferrari
Keyword(s):  
Power Systems ◽  
Acoustic Cavitation ◽  
Vapour Phase ◽  
Cavitation Number ◽  
Homogeneous Mixture ◽  
Hydrodynamic Cavitation ◽  
Hydraulic Power ◽  
Two Phase ◽  
Advantages And Disadvantages ◽  
Propagation Of Waves

Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh–Plesset equation are examined.

scholarly journals The transition from sheet to cloud cavitation

2017 ◽  
Vol 817 ◽  
pp. 439-454 ◽  
Author(s):  
P. F. Pelz ◽  
T. Keil ◽  
T. F. Groß
Keyword(s):  
Reynolds Number ◽  
Cavitation Number ◽  
Wall Friction ◽  
Bubble Collapse ◽  
Penetration Length ◽  
Cloud Cavitation ◽  
Viscous Film ◽  
History Of ◽  
Good Agreement

Recent studies indicate that the transition from sheet to cloud cavitation depends on both cavitation number and Reynolds number. In the present paper this transition is investigated analytically and a physical model is introduced. In order to include the entire process, the model consists of two parts, a model for the growth of the sheet cavity and a viscous film flow model for the so-called re-entrant jet. The models allow the calculation of the length of the sheet cavity for given nucleation rates and initial nuclei radii and the spreading history of the viscous film. By definition, the transition occurs when the re-entrant jet reaches the point of origin of the sheet cavity, implying that the cavity length and the penetration length of the re-entrant jet are equal. Following this criterion, a stability map is derived showing that the transition depends on a critical Reynolds number which is a function of cavitation number and relative surface roughness. A good agreement was found between the model-based calculations and the experimental measurements. In conclusion, the presented research shows the evidence of nucleation and bubble collapse for the growth of the sheet cavity and underlines the role of wall friction for the evolution of the re-entrant jet.

Competitive removal of DOM and bromide in raw waters by MIEX and iron coagulation

2013 ◽  
Vol 13 (1) ◽  
pp. 123-129
Author(s):  
Zhizhen Xu ◽  
Ruyuan Jiao ◽  
Xiaomin Yan ◽  
Dongsheng Wang ◽  
Mary Drikas ◽  
...  
Keyword(s):  
High Performance ◽  
Fluorescence Spectra ◽  
Ion Exchange Resin ◽  
Disinfection Byproducts ◽  
Size Exclusion ◽  
Low Molecular Weight ◽  
Raw Water ◽  
Potential Risks ◽  
Safety Of Drinking Water ◽  
Magnetic Ion

Dissolved organic matter (DOM) and bromide as principal precursors to halogenated disinfection byproducts (DBPs) have potential risks on the safety of drinking water after disinfection. Removal of DOM and bromide in raw water from two different waterworks using magnetic ion exchange resin (MIEX), ferric coagulation and their combination was investigated. Results showed that as MIEX dose increased, DOM and bromide coexisting in raw water could be removed effectively. DOM tended to be mainly removed by MIEX at low dose (<4 mL/L), regardless of the bromide concentration. Bromide could compete for exchange sites with DOM at high MIEX dosage (>4 mL/L). The fluorescence spectra and high performance size-exclusion chromatogram analysis indicated that at low MIEX dosage, bromide decreased the removal of low molecular weight (MW), soluble microbial byproduct-like and aromatic protein-like organic matters, which had lower affinity with MIEX in raw water. The removal of high MW humic acid, which presented greater affinity with MIEX, was not influenced at low MIEX dose but decreased at high MIEX dose with the addition of bromide. The combination of MIEX and ferric coagulation significantly enhanced the removal of DOM and reduced the requisite ferric dose by at least 67% compared to coagulation alone.

scholarly journals A novel advanced technology for removal of phenol from wastewaters in a Ventury reactor

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 1935-1942 ◽  
Author(s):  
Sandra Petkovic ◽  
Borivoj Adnadjevic ◽  
Jelena Jovanovic
Keyword(s):  
Waste Water ◽  
Cavitation Number ◽  
Hydrodynamic Cavitation ◽  
Advanced Technology ◽  
Phenol Removal ◽  
Waste Waters ◽  
Coal Processing ◽  
Technological Parameters ◽  
Novel Technology ◽  
Temperature Time

Phenol is a major pollutant in the waste waters coming from coal processing. Hydrodynamic cavitation presents a novel technology for phenol removal from waste waters. Hydrodynamic cavitation device with a cavitator of Ventury type for waste water purification was constructed. The hydraulic characteristic of the device were determined: the dependences of flow and cavitation number on inlet pressure. The effects of cavitation number, phenol concentration, pH, temperature, time, and quantity of added H202 on the degree of phenol reduction in the waste water was investigated. The optimal technological parameters of the investigated cavitation purification process of waste waters from phenol were determined.

HYDRODYNAMIC CAVITATION USING DOUBLE ORIFICE- PLATES FOR THE GENERATION OF HYDROXYL RADICALS

2016 ◽  
Vol 78 (11) ◽  
Author(s):  
Muhammad Noor Hazwan Jusoh ◽  
Azmi Aris ◽  
Juhaizah Talib
Keyword(s):  
Reaction Time ◽  
Hydroxyl Radicals ◽  
Potassium Iodide ◽  
Cavitation Number ◽  
Hydrodynamic Cavitation ◽  
Total Flow ◽  
Flow Area ◽  
Orifice Area ◽  
Single Plate ◽  
Double Orifice

The generation of hydroxyl radicals (OHŸ) by hydrodynamic cavitation (HC) using single and double orifice plates was studied. Five orifice plates with different configurations (size and number of orifice, total orifice area) were tested. The formation of OHŸ was measured by iodide dosimeter method using spectrophotometer at 355 nm wavelength. The effects of plate configurations and double plate arrangements on OHŸ generation were investigated in 60 minutes of reaction time using an inlet pressure of 45 psi and initial potassium iodide (KI) concentration of 20 g/L. The generation of OHŸ were expressed in terms of concentration and percentage of increase of iodine liberation. The liberated iodine for single plate ranged from 0.26 to 0.56 g/L (84 to 180% increase). The highest liberation was achieved using plate with the lowest total flow area of orifice, which had the smallest cavitation number. The double plate arrangement produced the highest iodine liberation (1.30 g/L; 420% increase) with the highest cavitational yield (2.9 x 10-1 mg/J) as compared to those of single plate arrangement. In double plate arrangement, the enhancement was dependent on the configuration and arrangement of the plates.

scholarly journals Cavitating Flow through a Micro-Orifice

Micromachines ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 191 ◽  
Author(s):  
Zhi-jiang Jin ◽  
Zhi-xin Gao ◽  
Xiao-juan Li ◽  
Jin-yuan Qian
Keyword(s):  
Pressure Difference ◽  
Rapid Development ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Hydrodynamic Cavitation ◽  
Apparent Difference ◽  
Microfluidic Systems ◽  
Vapor Cavity ◽  
Exit Pressure ◽  
Flow Through

Microfluidic systems have witnessed rapid development in recent years. As one of the most common structures, the micro-orifice is always included inside microfluidic systems. Hydrodynamic cavitation in the micro-orifice has been experimentally discovered and is harmful to microfluidic systems. This paper investigates cavitating flow through a micro-orifice. A rectangular micro-orifice with a l/d ratio varying from 0.25 to 4 was selected and the pressure difference between the inlet and outlet varied from 50 to 300 kPa. Results show that cavitation intensity increased with an increase in pressure difference. Decreasing exit pressure led to a decrease in cavitation number and cavitation could be prevented by increasing the exit pressure. In addition, the vapor cavity also increased with an increase in pressure difference and l/d ratio. Results also show the pressure ratio at cavitation inception was 1.8 when l/d was above 0.5 and the cavitation number almost remained constant when l/d was larger than 2. Moreover, there was an apparent difference in cavitation number depending on whether l/d was larger than 1.

Sign in / Sign up

Export Citation Format

Share Document