Water Pasteurization Indicator (WAPI)

Product Description

The Water Pasteurization Indicator (WAPI) is an open-source hand-made thermometer that indicates when water has reached pasteurization temperature and is safe to drink. Rather than waiting for water to boil (which occurs at 100 °C and is far beyond the required temperature for destroying microorganisms), a WAPI uses a melting wax to indicate that water has reached 65 °C. This saves fuel by eliminating the need to boil water to ensure that the pasteurization temperature has been reached.

Target SDGs

SDG 6: Clean Water and Sanitation

SDG 3: Good Health and Well-Being

Market Suggested Retail Price

$10.00

Target Users (Target Impact Group)

Household

Distributors / Implementing Organizations

Many organizations have made and distributed WAPIs including Agua Pura Para el Pueblo and Rotary International Clubs (such as Buford/North Gwinnett, Calabasas, and Monterey Sunrise).

Manufacturing/Building Method

WAPIs are built using openly available instructions that require the following materials: Polycarbonate tubing (3/8” OD, 1/4” ID), wax (Myverol 18-06), a washer (18-8ss, 1” OD, 3/8” ID), 2 single barrel compression sleeves, and a wire “S” hook.

Intellectural Property Type

Open-source

User Provision Model

Construction manuals and instructional videos for building WAPI’s are openly available online. Links can be also be found in Research & standards section.

Distributions to Date Status

Unknown

Deactivation mechanism

Pasteurization

Energy source

None

Manufacturer-specified water treatment rate (L/hr)

Not applicable

Bacteria reduction

6 log

Virus reduction

4 log

Protozoa reduction

Unknown

Heavy metals and/or arsenic reduction

Unknown

Maximum recommended influent turbidity level (NTU)

Not applicable

Effluent turbidity levels (NTU)

Does not reduce turbidity

Safe water storage capacity (L)

None

Design Specifications

A WAPI consists of Myverol 18-06 soy wax that is housed inside a sealed clear tube. When submerged in water with wire and washers, the wax will melt from one end of the clear tube to the other at 65 °C. WAPI’s are symmetrical and thus can be repeatedly used by simply flipping them over.

Product Schematics

Technical Support

None available

Replacement Components

Components must be locally purchased

Lifecycle

Unknown

Manufacturer Specified Performance Parameters

Wax must melt at 65 °C.

Vetted Performance Status

Water pasteurization is well known to be effective against microorganisms (bacteria, viruses, and protozoa). Specifically, the WAPI has been used by academic organizations to test water pasteurization in low-resource situations.

Safety

Treated water should be stored in a clean container to avoid recontamination. Pasteurization does not treat water contaminated with salt or other chemicals.

Complementary Technical Systems

Solar or biomass-powered pasteurization.

Academic Research and References

Rolla, T.C., Sun and water: an overview of solar water treatment devices, Journal of Environmental Health, 1998, 60(10).

Metcalf, Robert, “The microbiology of solar water pasteurization, with application in East Africa” a report by WAPI designer.

Safapour, N., Metcalf, R.H., Enhancement of solar water pasteurization with reflectors, Applied and Environmental Microbiology, 1999, 65(2), 859-861. (this study uses the WAPI as an indicator for pasteurization)

Solar Pasteurization, A chapter in Drinking Water Treatment by Ed Pejack (pages 37-54)

Kang, G., Roy, S., Balraj, V., Appropriate technology for rural India – solar decontamination of water for emergency settings and small communities, Transactions of The Royal Society of Tropical Medicine and Hygiene, 2006, 100(9), 863-866.

N. Safapour and R. H. Metcalf, “Enhancement of solar water pasteurization with reflectors,” Appl. Environ. Microbiol., vol. 65, no. 2, pp. 859–861, 1999.

T. C. Rolla, “Sun and water: an overview of solar water treatment devices,” J. Environ. Health, vol. 60, p. 30+, 1998.

“WAPI Flyer,” Monterey Peninsula Sunrise Rotary Club. Available: http://www.montereysunriserotary.org/wapi-flyer.html

“Agua Pura para el Pueblo,” Aguapuraparaelpueblo.org. Available: https://www.aguapuraparaelpueblo.org/

“Water Projects,” FFYIA. Available: https://www.florenceforyouthinaction.org/waterprojects

“Water Pasteurization Indicator (WAPI),” Engineering For Change. Available: http://old.engineeringforchange.org/solutions/product/water-pasteurization-indicator-wapi/

“Multi-Fuel Water Pasteurization Indicator (WAPI),” Sun Oven The Original Solar Oven and Solar Cooker, 29-Apr-2020. Available: https://www.sunoven.com/product/water-pasteurization-indicator-wapi/

“Goal 6,” Sdgs.un.org. Available: https://sdgs.un.org/goals/goal6

“Agua Pura para el Pueblo,” Aguapuraparaelpueblo.org. Available: https://www.aguapuraparaelpueblo.org/?p=663

“Water Pasteurization Indicator,” Solar Cooking. Available: https://solarcooking.fandom.com/wiki/Water_Pasteurization_Indicator

“What is a Wapi or Water Pasteurization Indicator?,” Write Studio, 08-Oct-2012. Available: https://www.writestudio.com/304/water-pasteurization-indicator

“The microbiology of solar water pasteurization, with applications in east Africa,” Nocookie.net. Available: https://static3.wikia.nocookie.net/__cb20101207224924/solarcooking/images/a/a0/Granada06_robert_metcalf.pdf

Compliance with regulations

Pasteurizing water can reduce microorganism concentration to levels recommended by the WHO.

Evaluation methods

WAPIs have been evaluated and shown to reduce microorganism concentrations when the wax melts at 65 °C. Additional field tests and user reports have shown their durability and usability.

Other Information

None

Comments from the Community

3 Comments

Steve Harston says:

October 21, 2016 at 3:42 pm

It’s unclear to me how this product is intended to be used. Is it intended to be a stationary or mobile device? If it is a stationary device, what is the advantage of the GPS? This is probably a cool design feature but the value of it is not described anywhere. Is this cooler intended to be plugged into the wall the majority of the time with a battery backup? Is it powered by a solar panel? Is it completely passive where the ice packs are removed and frozen in an external freezer?
Laura MacDonald says:

February 27, 2017 at 7:45 pm

â€¢Rebranded to Safe Water Book
â€¢Also filtration? What is the primary mechanism – filtration or disinfection?
â€¢How do you have a “user provision model” already if itâ€™s still a prototype?
â€¢Price not $0, not being sold yet
â€¢Any information on flow rate through the bookâ€™s page?
Anna Murray says:

September 14, 2017 at 6:05 am

Agree about confusion between filtration and disinfection as the method of treatment. It’s a little misleading to have this listed alongside disinfection products.