Low-Cost Water Purifier for Third World Countries

Open-source plans for a water purifier utilizing an electric arc

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The goal of this project is to create a water purifier based on UV disinfection or pulsed corona discharge.

UV Waterworks is an example of a highly successful UV water purifier. However, the system does cost $300:

There are also other smaller UV purifiers, such as the SteriPen Sidewinder Water Purifier:
This system is a bit on the expensive side. Also, in the case a third world country, it would be better to have a system that could provide more water, and that is more robust.

My intention is to develop a better solution: one that could be built easily, and cheaply by anyone. It will be a balance betwen UV Waterworks and the Sidewinder.

My intention is to utilize an electric arc to produce the UV light instead of a bactericidal lamp. This has three possible advantages:

1) Lower cost

2) Longer lifetime (Except in the case of an LED, but those are expensive)

3) An electric arc produces OZONE. This should aid in the disinfection of the water. Also, ozonated water can be used to clean surfaces! In other words, this project could have two applications! Could it be used to clean food? Perhaps!:

4) Pulsed corona discharge is an option (something to look into) :

The system will be powered by supercapacitors (easy to charge, very robust, high current capability). The supercapacitors will be charged by solar panels or a crank generator.

My plan so far is to build the system from 4 inch PVC. PVC is readily available, and strong.

Main Objectives:

1) Total cost < $40 (assuming you don't already have some of the parts)

2) Can provide enough water to sustain at least 20 people.

3) Easy to construct; anyone with clear instructions can build it with few tools.

4) Very robust

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  • Testing the Water Purifier

    NathanStrachen06/03/2016 at 04:28 0 comments

    The strip on the right was treated with the purifier for 30 sec. It looks like it definitely did something.

  • Filter Assembled

    NathanStrachen05/29/2016 at 15:46 0 comments

    The next step will be to work on the electronics. Sadly, my high voltage module suddenly died. I think I know why (I will explain this later). I have ordered another one to experiment with. Hopefully I can get this module to work reliably for a long time. If not , I will most likely resort to using a flyback transformer taken from a CRT.

    I have some bacteria testing strips for water that I can use for proof of concept. I will have to resort to more precise analysis down the road.

  • Spark Gap Assembled

    NathanStrachen05/29/2016 at 15:34 0 comments

    4-40 stainless steel screws were bent to form the spark gap.

  • PVC Parts Purchased

    NathanStrachen05/29/2016 at 15:12 0 comments

  • PVC Construction

    NathanStrachen05/28/2016 at 17:51 0 comments

    A basic sketch of the physical construction of the filter (precise length will be decided later). Besides drilling two holes in the PVC plug and endcap, you pretty much just fit the PVC parts together.

  • Testing the High Voltage Module

    NathanStrachen05/28/2016 at 01:34 0 comments

    The high voltage module was tested with a 25 F supercapacitor, charged to 4.93 V. The module ran for 30 sec, producing arcs of about a cm in length. A voltage of 1.35 V was then measured on the capacitor.

    Questions to ask:

    1) How much water will 30 sec. of run time purify (With just the UV light) ?

    2) How long would a solar panel take to charge the supercapacitor? (assuming I purchase one within my budget)

    These will be investigated in future experiments.

    This little module packs quite a punch. I have attached a video of it.

  • High Voltage Source

    NathanStrachen05/27/2016 at 15:49 0 comments

    For the high voltage, there are two main ideas:

    1) Flyback transformer stolen from a CRT TV set:

    One could perhaps make use of the tremendous amount of e-waste in third world countries. On second thought, having to disassemble a CRT does not exactly make it easy to assemble. Its still an idea though.

    2) High Voltage Module:

    I really like this module for several reasons. First, it is very affordable, and very easy to use. I recently received one in the mail, and it is very powerful for its size. Its the perfect HV supply for a supercapacitor, because of its low voltage, high current input.

    My only concern is the lifetime of the device. I suspect that proper care of the device will result in a very long lifetime.

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ianpaull wrote 05/08/2019 at 16:52 point

Is it more efficient to proceed as you suggested with a hand crank generator, charge electronics into supercaps, then HV generator circuitry to the arc or would it be better to hand crank a static generator directly to HV? Van de Graff requires only mechanical parts, easier to come by in third world locales.

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