Water Treatment Using Ultrasound-Induced Cavitation

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Water Treatment Using Ultrasound-Induced
Cavitation
Michael Anderson Mechanical Engineering Center
for Intelligent Systems Research Greg Möller
Food Science and Toxicology
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• Experts consider options over sources of city
  water
• Associated Press, September 20, 2004
• TWIN FALLS, Idaho After years of drought and a
  declining Snake River Aquifer, experts are not
  ruling out any local lakes or even wastewater
  plant effluent as a source of city water.
• Just five years ago, Twin Falls thought it had
  accumulated enough water sources to last for 50
  years. Considering that diminishing supply, the
  city now finds itself pretty much starting over.
• But since the first plan was devised, rounding up
  that water has become more complicated. The
  federal government recently said Twin Falls must
  lower naturally occurring arsenic levels in about
  40 percent of its supply.
• A committee is looking at a number of sources for
  water along the Snake River Canyon, including
  Devil's Corral, Rock Creek, seepage tunnels and
  wastewater treatment plant effluent. It's also
  working with state officials to change the use of
  certain water rights to purchase them.

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Problem Statement

• Water quality and quantity is vitally linked to
  public health, environmental quality and economic
  opportunity.
• Many communities are now development limited
  due to limited water supply and limited
  wastewater discharge opportunity.
• New science suggests bioactive substances in
  human wastewater and other discharges are a
  direct threat.

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Disinfection
Clarifiers
Secondary Aeration
Primary Settling
Solids Digestion
Pump Screen
NPDES Permit to Pollute
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Challenges

• Pharmaceuticals, endocrine disrupting substances,
  personal care products, and various pesticides
  and herbicides are found in many natural waters.
• Wastewater discharge and non-point source
  pollution.
• Micropollutants, PPCPs, PhAS, Biocidals.
• Concern about environmental and public health
  impact of these substances.
• Need for better science and technology.
• Disposal and treatment options.
• Detection of chemicals and biological impacts.
• Green science and engineering.

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Example Antibiotic Soap

• Triclosan, the common antiseptic, was found in
  57.6 of the United States water resources
  surveyed (USGS).
• A broad-spectrum antibacterial - antimicrobial
  agent classified as a Class III drug by the FDA.
• Bacteriostatic activity against a wide range of
  bacteria has lead to popular use in
• Personal care products, cosmetics, anti-
  microbial creams, acne treatment, lotions and
  hand soaps, plastics, polymers and textiles.
• Linked to estrogenic effectsin fish.

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Micropollutants in U.S. Waters

• USGS study tested U.S. waters for 95 chemicals
  ranging from perfumes to antidepressants.
• Of 139 streams tested, 80 had at least one of
  the chemicals and 50 had seven or more.
• Continual introduction ? persistence.
• Threat to water reuse and to captive aquatic
  biota.

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Excretion

• When we take medication, our bodies excrete the
  active chemicals with as much as 90 of the
  ingested drug still in a potent form.

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Endocrine Disrupters

• Chemicals which interfere with endocrine system
  function.
• Endocrine system consists of glands and the
  hormones they produce.
• Pituitary, thyroid, and adrenal glands, the
  female ovaries and male testes.

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Male-to-Female Sex Reversal

• Salmon a high incidence (84) of a genetic
  marker for the Y chromosome in phenotypic females
  sampled from the wild... It appears likely that
  female salmon with a male genotype have been sex
  reversed, creating the potential for an abnormal
  YY genotype in the wild that would produce
  all-male offspring and alter sex ratios
  significantly.
• High Incidence of a Male-Specific Genetic Marker
  in Phenotypic Female Chinook Salmon from the
  Columbia River. Nagler, JJ Bouma, J Thorgaard,
  GH Dauble, DD Environmental Health
  Perspectives. Vol. 109, no. 1, pp. 67-69. Jan
  2001

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HypospadiasIncomplete Masculinization of the
Reproductive Tract

• Paulozzi LJ, Erickson JD, Jackson RJ. 1997.
  Hypospadias trends in two U.S. surveillance
  systems. Pediatrics 100831-834.
• Paulozzi LJ 1999. International trends in rates
  of hypospadias and cryptorchidism. Environmental
  Health Perspectives 107297-302.
• Gray, LE, C Wolf, C Lambright, P Mann, M Price,
  RL Cooper and J Ostby. 1999. Administration of
  potentially antiandrogenic pesticides
  (procymidone, linuron, iprodione, chlozolinate,
  p,p'-DDE, and ketoconazole) and toxic substances
  (dibutyl- and diethylhexyl phthalate, PCB 169,
  and ethane dimethane sulphonate) during sexual
  differentiation produces diverse profiles of
  reproductive malformations in the male rat.
  Toxicology and Industrial Health. 1594-118.

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Cavitation

• Oscillating pressure field (ultrasonic) or
  fluctuating pressure in shear layer of water jets
  (hydrodynamic) cause pre-existing microscopic
  bubble nuclei to grow explosively and then
  collapse violently.

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Simulated Cavitation Bubble Dynamics

• Sequence from high speed film of 1cm cavitation
  bubble collapse.
• Note formation of high speed re-entrant jet (3,4)

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2
3
4
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Pressure Field Associated with Bubble Collapse
Cavitational activity is directly proportional to
the number density of particles present in the
medium (Madanshetty and Apfel, 1991).
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Ultrasonic Water Treatment How Does It Work?

• Acoustic waves in water can resonantly vibrate
  gas bubbles
• Resonant vibration can result in violent bubble
  collapse, causing temperatures and pressures as
  high as 5000K and 1700atm
• High pressures and temperatures cause chemical
  reactions among the gas in the bubble and water
  vapor, one of them the dissolution of water into
  H? and OH? (free radicals).
• Free radicals diffuse into the water and oxidize
  harmful chemicals.

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How Hot?
New York Times, Tiny Bubbles Implode With the
Heat of a Star, March 15 2005
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Sonochemistry

• Free radicals are formed as a result of the
  cavitation microbubbles which are created during
  the negative pressure period of sound waves
• Acoustic vs hydrodynamic
• Dissolved gas nucleation sites needed
• Ozone
• Milder operating conditions
• Lower T, P

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Postulated Reaction Mechanisms and Locations

• Within bubble.
• Hydroxyl and other radical attack in gas phase.
• Pyrolysis in gas phase.
• Ion reactions.
• At or near bubble surface in liquid.
• Hydroxyl and other radical attack in liquid
  phase.
• Formation and reaction with supercritical water.
• In bulk liquid solution.
• Hydroxyl and other radicals attack in liquid
  phase.
• Intermediate reactions and reaction products.

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Mechanism of Cavitation OxidationAdvanced
oxidation process

• Water dissociates under extreme physical
  conditions generated at cavitation bubble
  collapse.
• Calculated up to 5-10,000K and 500-1200 atm
  (?sec lifetime).
• Forms free radicals
• H2O ? H? OH?
• H? H? ? H2
• OH? OH? ? H2O2
• OH? ORGANIC ? CO2 H2O

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Higher Frequency UltrasonicsMegasonics 1MHz

• Current research is finding that for oxidations
  higher frequencies may lead to higher reaction
  rates.
• More, smaller, faster collapsing bubbles
• Less ?OH radical recombination?

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Rayleigh-Plesset Equation
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Resonance Frequencies Air Bubbles in Water
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Moderate Vibration
Source Leighton, The Acoustic Bubble,
Academic Press, 1994
Ro 2 mm, fo1.7 kHz f 10 kHz PA 2.4 bar
0.27 MPa
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Stable Cavitation
Ro 0.10 mm, fo? 10 kHz f 10 kHz PA 2.4 bar
0.24 MPa
Source Leighton, The Acoustic Bubble,
Academic Press, 1994
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Stable Cavitation
Made by Tom Matula, Applied Physics Laboratory,
University of Washington, available on Wikipedia
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Transient Cavitation
Ro 60 ?m
Ro 50 ?m
f 10 kHz PA 0.24 MPa
Ro 10 ?m
Ro 1 ?m
Source Leighton, The Acoustic Bubble,
Academic Press, 1994
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Spectra for Stable and Transient Cavitation
Source Frohly, et al., JASA, 108(5), 2012-2020,
2000
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Spectra for Stable and Transient Cavitation
Source Frohly, et al., JASA, 108(5), 2012-2020,
2000
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Spectra for Stable and Transient Cavitation
Source Frohly, et al., JASA, 108(5), 2012-2020,
2000
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Effect of Pressure Amplitude on Acoustic
Cavitation
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State of the Art- Water Treatment
Source Destaillats, et al., Ind. Eng. Chem.
Res., 40, pp. 3855-3860, 2001
3096 J/Liter for ½ removal MO _at_ 67 W/Liter
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Diffusion of Ultrasound in Tube Reactor
Total Length of Tube 120 cm Tube Diameter 9
cm
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Collimator to Diffuse Ultrasound
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Pilot Scale Flow Ultrasonic Cavitation 5 Cell
Apparatus and Filter Radiator Design
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High Achievable Energy Densities
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Luminol Chemi-Lumeniscence
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Ultrasound Distribution
100 Drive 100 Watts 15.1 W/Liter 70
Drive 43 Watts
Length of Tube 55 cm Measurement 15 cm from
transducer
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Spectra at Low Power
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Spectra at High Power
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Test Reactor Sonochemical Measurements
Diameter 7.5 cm Length 27 cm Volume 1.2
Liter 0.7 MPa at 95 Watts Typical 80
Watts/Liter
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Relative Oxidizing Strength
Standard Potential (V)
Hydroxyl radical 2.80
Ozone 2.18
Chlorine 1.68
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Redox Potential 18 MO-cm Water
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Fe2/Mn2 Oxidation
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Potassium Iodide
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Potassium Iodide
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Potassium Iodide
3096 J/Liter for ½ removal MO _at_ 67 W/Liter
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Indigo Carmine Dye Bleaching
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Observations/Conclusions

• 0.7 MPa achieved at 15 W/Liter in 3.5 Liter
  volume.
• Sonochemical activity caused by stable
  cavitation. Potential for increased performance
  with transient cavitation.
• At 0.7 MPa and 56 W/Liter, measured 6180 J/Liter
  for t1/2 KI in 1 Liter volume (possibility for 15
  W/Liter with tube reactor).
• Compares with unknown pressure, 67 Watt/Liter,
  3096 J/Liter for t1/2 MO in 45 Liter volume.

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UI Intellectual Property

• Parabolic transducer source (6,818,128)
• Radiator tube reactor array (6,911,153)
• Biphasic/triphasic US/ozone/metal-oxide catalytic
  water filter (patent pending)

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Indigo Carmine Dye Bleaching
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Indigo Carmine Dye Bleaching
3096 J/Liter for ½ removal MO _at_ 67 W/Liter
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Acoustic Measurements
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How Hot?
Chemical and Engineering News, Bubble Inferno,
2005, 83, 10.
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How Hot?
Science, 2002, 295, 1868.
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How Hot?
Science News, 2005, 167, 147.
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Amplitude of Fundamental
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Amplitude of 1st Harmonic
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Endocrine Disrupters

• Hormones are biochemicals.
• Produced by endocrine glands.
• Travel through the bloodstream and cause
  responses in other parts of the body.
• Hormones of primary concern.
• Estrogen, androgen and thyroid hormones.

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Antidepressants

• With the introduction of a host of new
  anti-depression drugs in the late 80s,
  antidepressant prescriptions grew from 40 million
  in 1988 to more than 120 million in 1998.
• According to the CDC National Center for Health
  Statistics, more than 61 million new
  prescriptions for antidepressants were given by
  U.S. doctors in 2001.

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Antidepressants in Biota

• Prozac, Zoloft, Paxil and Celexa (selective
  serotonin reuptake inhibitors) are found in biota
  downstream of WWTPs (B. Brooks, Baylor U.)
• Levels of antidepressants as low as 1.5 ppb
  delays frog metamorphosis and cause development
  problems in fish (M. Black, U. GA).

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Newton, Iowa WWTP
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Pharmaceuticals

• Prescription drug sales in the U.S. have
  increased by 16.9 to 172 billion in 2003, plus
  18 billon in over-the-counter medicines.
• The Union of Concerned Scientists estimates that
  in the U.S., 25 million pounds of antibiotics are
  fed to animals each year compared to 8 million
  pounds for people.