Talk:Projects/WaterPurifier

UV Light Water Purifier Discussion

OLPC Category

• http://wiki.laptop.org/go/Water_and_sanitation

OLPC Responses

Nathan Riddle

The maximum output of the USB port is 1 amp (5 watts at 5 volts). The maximum output of the power module is 1.42 amps (about 16 watts at 12 volts).

Water purifiers are roughly 5 watts for one gallon per minute. If you are just purifying a glass of water, units are available that use a couple of AA batteries (3.5 volts).

A UV lamp is a fluorescent lamp with a quartz "glass" (in case of high efficiency models) and as such is a high voltage discharge tube. Some type of transformer (ballast) is needed to step up the volage to operate the lamp -- these are separate modules or may be built into the lamp base as in the case of compact fluorescent lamps. Voltages are about 150 volts or higher to start the discharge and may drop to 90 volts for operation.

Wires held with tension (clips) can be substituted for sockets (or electrical tape, for example, or wires glued against the contacts).

In the hobby market there are six inch fluorescent lamps. These are operated by 6 volt or 12 volt lantern batteries using a small (1" square) circuit board and draw less than 1/2 amp.

Now, if Christian can supply the description of the lamp purchased from Amazon, maybe a ballast can be found to operate from the 12 volt power supply used for the XO (or maybe from the USB port for low amounts of water). The ideal is to just buy a water purification arrangement that has a ballast that is powered by 5 or 12 volts.

Corbin bought:  http://www.amazon.com/gp/product/B0027ND0VO - Christian Bryant

In any case, the lowest cost equipment appears to be in aquarium and pond germicidals. A 3 watt UV lamp and a separate electronic ballast (120 volt) can be had for $25.

• http://www.soslightbulbs.com/gtl3-uv-germicidal-lamp.aspx

There is a multitude of example circuits on the internet for electronic ballasts powered by 5 to 12 volts (as well as some in the local electronic parts store).

I would suspect that some type of germicidal lamps are available in country and simple ballasts for low voltage power could be obtained or constructed from components shipped into country.

Drinking water germicidals for 2 gpm can be had for about $200 (U.S).

Chris Leonard

If you have enough sun to charge your XO, you have enough solar to use plastic soda bottles (ideally PET) on a tin roof in a solar water purification approach, a tried and true method, well-documented. I must believe that more UV radiation comes from the sun (especially in the tropics) than you will generate by converting light to electricity and then back to UV through an intentionally low power system.

I think the benchmark for capacity and cost-effectiveness should be SODIS:

• http://www.appropedia.org/Solar_water_pasteurization
• http://en.wikipedia.org/wiki/Solar_water_disinfection