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Solar Water Pasteurization

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Solar Water Pasteurization Dale Andreatta, Frank Husson, Robert Metcalf October 16, 2013 Water and Health Conference Chapel Hill, North Carolina 400 Liters per hour ... – PowerPoint PPT presentation

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Title: Solar Water Pasteurization


1
Solar Water Pasteurization
  • Dale Andreatta,
  • Frank Husson,
  • Robert Metcalf
  • October 16, 2013
  • Water and Health Conference
  • Chapel Hill, North Carolina

2
Presenters
  • Dale Andreatta, Ph.D. in mechanical engineering,
    designer of pasteurizers, Columbus, Ohio.
    (Presenter)
  • Frank Husson, president of Solar Solutions,
    designer of pasteurizers, San Diego, California.
    (Present today)
  • Robert Metcalf, Ph.D. in microbiology, promoter
    of water pasteurization and solar cooking,
    Sacramento, California. (Currently in Africa)

3
Bob Metcalf is in Kenya at a water conference
4
Basics of Pasteurization
  • Pasteurization A heat process that kills all
    disease-causing microbes (pathogens) including
    cryptosporidium.
  • First discovered by Louis Pasteur 150 years ago.
  • Hepatitis A is the most heat resistant pathogen,
    but is killed by a few minutes at 65 C.
  • Not necessary to boil the water, as many believe.
  • Process is not affected by turbidity or acidity
    of water.
  • World Health Organization now says thermal
    processing, rather than boiling.
  • Thermal processing (boiling or pasteurization) is
    identified as the most effective method of
    biological pathogen eradication in the 2012
    Household Water Treatment handbook from WHO.
  • Heat denatures the proteins, similar to cooking
    an egg white (which can also be done at 65 C.

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D values (90 reduction times) bacteria in water
seconds at Bacterium 55C 60C
65C E.coli 0157H7 223 67 3 Shigella
sonnei 354 54 3 Salmonella
tyhpimurium 77 4 lt2 Ref A.
Spinks et.al, Water Research 401326-1332 (2006)
9
Just as with milk pasteurization, temperatures
well below boiling will kill microbes in water.
10
Why is Boiling the Standard Treatment?
  • Until 1992 there was no practical way to know
    whether the pasteurization temperature has been
    achieved.
  • In 1992, the first Water Pasteurization Indicator
    (WAPI) or Indicator was designed.
  • Several other indicators have since been
    developed.

11
Pasteurization
  • This talk is primarily about solar
    pasteurization, but we also include fuel-based
    pasteurization.
  • Indicators work in all sizes and shapes of water
    vessels.
  • Typically, solar heating is very slow, so you get
    a 6 log reduction (99.9999) in all pathogens by
    the time you reach 65 C.

12
Two Types of Indicators
Petroleum Wax Initial position Melts at 65 C
If found here later, 65 C was reached
13
Water Pasteurization Indicators Also known as
WAPIs or Indicators
  • This is an indicator, not a thermometer. Even if
    the water has cooled down, it still indicates
    that the water attained the required temperature.
  • Only tells whether required temperature was
    reached.
  • Indicator sits in the bottom of the water, where
    the coolest water is located.
  • Inexpensive and reusable.

14
Pasteurization vs. Boiling
  • With the necessary temperature of 65 C, about ½
    the energy can be saved compared to boiling.
    Indicator alone saves 50 of energy.
  • Solar plus indicator saves 100 of fuel.
  • Much easier to achieve 65 C than boiling
    temperature, so simple solar devices are viable.
  • Solar on sunny days, fuel heat on cloudy days (or
    chlorine).

15
Real Purpose of This Talk
  • To provide information, yes, but
  • The real purpose is to stimulate your thinking.
  • Where, how, under what conditions can
    pasteurization be used?
  • What niche(s) does pasteurization fill?

16
How to Pasteurize Water-Part 1
  • Batch Pasteurizers
  • Indicator is required

17
The Aqua Pak
  • The Aqua Pak is a dedicated batch pasteurizer,
    made of inexpensive plastic.
  • Can pasteurize 4-5 liters at a time.
  • Small glass indicator built into the cap.
  • Cost is about 2 if made in the developing world.
    Currently available, made in San Diego.
  • The plan is for independent entrepreneurs to set
    up a series of factories, copying the product and
    the process of making it.

18
Aqua Pak in Use
19
Aqua Pak is multi-function
  • The Aqua Pak is intended as a pasteurizer, but
    also as a transport, storage, and
    anti-recontamination (with its small opening)
    vessel.
  • Pasteurization can be achieved while on the move,
    as long as sunlight is hitting the transparent
    top.
  • Aqua Pak comes with chlorine tablets for cloudy
    days, and a filter for filtering the water.

20
The Solar Puddle, A Large Batch Pasteurizer
Basic Solar Puddle, built into the
ground. Horizontal dimensions compressed for
clarity.
21
The Solar Puddle
  • The solar puddle has been tested and studied
    extensively.
  • Over 80 C can be achieved with thin water layers
    (25 mm).
  • Pasteurization temperatures can be achieved with
    up to 75 mm water depth. This is 75 liters of
    water for a 1 square meter puddle.
  • Many variations possible.
  • Basic version is built into the ground, but
    benchtop puddle is also possible with wooden
    sides.
  • Basic version has 4 or 5 plastic layers, but
    bubble wrap can be substituted.

22
Two benchtop solar puddles Bubble wrap top
layer on left. Two-layer top layer, on right,
with top layer removed.
23
Pot-based pasteurizers
24
Test Results
  • Limited testing to date, due to issues with
    latitude and cloudy weather in Ohio.
  • 70 C was achieved on a mostly sunny day at 40
    North latitude. About 6.5 liters pasteurized.
  • Larger pots tested, 29 liters, 55 C achieved for
    1 hour.
  • The key to performance is that the grass gets hot
    quickly, transfers heat to the pot by convection
    and radiation.

25
Other Batch Pasteurizers
  • Other batch pasteurizers can be made from things
    including bottles, jugs, and sheets of plastic
    used to form a pouch.
  • Plain materials can be used, (grass, cheap
    polyethylene) though cheap plastic degrades in
    about 3 months because it does not have UV
    inhibitors added. The polyethylene in the Aqua
    Pak has 36 months of UV inhibitor added.
  • Any kind of solar cooker can also be a
    pasteurizer.

26
Simple Solar Cooker Being Used as a Pasteurizer
27
Summary of Batch Pasteurization
  • Batch pasteurization is simple, effective, and
    can be very low in initial cost.
  • An indicator is required.
  • Batch pasteurization is limited to modest amounts
    of water. Will always be in the Household Water
    Treatment and Storage category.
  • Can be combined with filtering, and chlorine to
    give residual disinfection.

28
How to Pasteurize Water-Part 2
  • Flow-Through Pasteurizers
  • Thermostatic valve is required

29
Flow-Through Water Pasteurizer Principle
Heater, Solar or Flame Heat
Heat Exchanger
Dirty Water, 20 C
60 C
Heat transfer From hot to cold
80 C
Clean water Out, 40 C
Thermostatic valve
30
Flow-through pasteurizers
  • Solar or flame heat can be used.
  • Process is automatic.
  • Outlet water is only warm, not hot.
  • You can use a heat exchanger to recycle the heat
    in the outgoing water, increasing the throughput
    by 3 times or more, while adding 50 or less to
    the cost.
  • Many experimental units have been built using
    solar, but no commercial solar units currently
    available.

31
InStove Water Pasteurizer
  • Institutional Stove Solutions, Cottage Grove,
    Oregon, builds large high quality wood-burning
    stoves for schools.
  • A new option is a flow-through pasteurizer using
    the large stove and large pot as the heater.
  • Much larger quantities of water can be
    pasteurized.

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400 Liters per hour at 10 grams of wood per liter
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InStove Water Pasteurizer
  • 100 effective against common harmful microbes in
    preliminary testing
  • Failsafe design unpasteurized water cannot
    leave the system
  • Can produce over 4000L of safe water per day
  • One unit provides drinking water for as many as
    1000 people
  • Optimized for use with InStove stoves
  • 20 times more energy efficient than boiling
    water over an open fire
  • Uses less than
  • - 10g of fuel per liter produced
  • - 4kg of fuel per hour
  • Designed for use in refugee camps, institutions
    (schools, hospitals, etc.), or as a small
    business
  • Cost is about 1000 for the stove and 1000 for
    the pasteurizer parts.

39
Limitations of Pasteurization
  • No residual disinfection, but you can add a
    little chlorine.
  • Doesnt improve appearance or taste, but you can
    add a filter.
  • Somewhat energy intensive.
  • Doesnt help with chemical or mineral
    contamination (most places only have biological
    contamination).

40
Summary
  • Pasteurization is one way of purifying water.
  • Very safe, very verifiable, low cost.
  • Somewhat energy intensive, so appropriate only
    for small to modest quantities of water.
  • No residual disinfection (unless coupled with
    chlorine) and does not improve taste, color,
    cloudiness (unless coupled with a basic filter).
  • Clearly, pasteurization is not the solution in
    all situations, but its potential has barely been
    touched.

41
Additional Information
  • Contact information
  • Where to get.
  • Further reading
  • A worldwide energy calculation

42
Contact Information
  • Dale Andreatta, Ph.D., dandreatta_at_sealimited.com
  • Frank Husson, fhusson_at_solarcleanwatersolution.com
  • Robert Metcalf, Ph.D., sac15166_at_saclink.csus.edu

43
Additional contacts, Solar Cookers International
  • For plastic indicators, Aqua Paks, and solar
    cookers.
  • 1919 21st St. Sacramento, California, US 95811
  • (916) 455-4499
  • info_at_solarcookers.org
  • www.solarcookers.org

44
Additional Contacts, Solar Solutions, LLC
  • For Aqua Paks, glass indicators, petroleum wax.
  • Solar Solutions, LLC 10080 Willow Creek Rd. San
    Diego, California, US 92131
  • Information_at_solarcleanwatersolution.com
  • (858) 695-3806 extension 4703

45
An Excellent Review of Water Purification
Technologies is
  • An Overview of Water Disinfection in Developing
    Countries and the Potential for Solar Thermal
    Water Pasteurization, by Jay Burch and Karen
    Thomas
  • Search for NREL/TP-550-23110

46
Worldwide Energy Consumption to Boil Water
  • If one billion people boil 4 liters of water per
    day for drinking, this requires about 4.58E17
    Joules of energy.
  • If they boil on wood stoves with 12 efficiency
    (also accounting for the fuel left unburned when
    the water reaches boiling) the amount of fuel
    burned will be 2.4E8 metric tons. This produces
    about 3.5E8 metric tons of carbon dioxide. This
    is about 1.2 of the total from fossil fuels,
    plus carbon monoxide and black carbon.
  • If they boil on propane stoves with 50
    efficiency, 1.9E7 metric tons of propane will be
    consumed, leading to 5.7E7 metric tons of carbon
    dioxide. This is about 0.2 of the yearly total
    from fossil fuels.
  • Regardless of the method, the global warming
    potential is significant, and could be reduced
    significantly with any of the techniques given
    here.

47
Papers by the Current Presenters
  • The Solar Puddle A Low-Cost Water
    Pasteurizer, Andreatta, Dale American Solar
    Energy Society, 2001
  • Inexpensive Personal Solar Water Pasteurizer,
    Husson, Frank Andreatta, Dale, American Solar
    Energy Society, 2003

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