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Potable Water

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Potable Water

Potable Water

  • Using transparent plastic bottles to purify drinking water:
Source:Talk:Peter Botterill

For DRINKING WATER LINKS try looking at: < > Go to “Treatment Processes” – page 8

It explains, among many other things, a very cheap system to follow for improving household drinking water by solar treatment – 90% filling transparent plastic bottles with clear water, shaking them to encourage the air to mix with the water, completely filling them and leaving each laid on its side, perhaps on a reflective corrugated iron sheet, in the sunlight for 6 hours on sunny days, for 2 days in cloudy weather. Then drinking straight from the bottle is recommended to avoid further contamination. The purpose of the exposure to the sun is to give the ultra-violet rays in sunlight a chance to kill or very much reduce any bacteria in the water. This water should NOT be stored but used as produced as a small quantity of residual bacteria could multiply quickly. (detail below)

Solar water disinfection

In solar water disinfection (SODIS), microbes are destroyed by temperature and ultra-violet light (UVA) radiation provided by the sun. Water is placed in a transparent plastic (PET) bottles, which is first oxygenated by shaking 90% partially water-filled capped bottles prior to filling the bottles all the way. The completely water-filled and capped bottles are exposed to sunlight, preferably on a corrugated metal roof, slanted slightly to maximize the exposure to solar radiation. In practice, the water-filled bottles are placed for six hours in full sun, or for two days in partial sunlight for weather conditions involving partially overcast days, which raises the temperature of the water and gives an extended dose of solar radiation to the water in the bottles, killing almost all microbes that may be present. The combination of the two effects (UVA and heat) provides a simple method of disinfection for use in tropical developing countries, or in survival situations.

The use of glass bottles may or may not provide the same degree of SODIS disinfection as using PET bottles. This is because most glass bottles are non-transparent or opaque over the wavelengths of sunlight required for successful UV disinfection from the solar spectrum required for solar water disinfection to work, and glass bottles are usually thicker than PET bottles, which further reduces the dose of UVA to the water inside glass bottles versus PET bottles. For cases where the UVA is blocked, or reduced, only the heating effects without adequate UVA exposure are typically at work if glass bottles are used, potentially leaving dangerous amounts of bacterial and viral loads within the water. This water should NOT be stored but used as produced as and small quantity of residual bacteria could multiply quickly.

This method might be improved with wrapping the underside of the bottle with reflective foil (held in place by rubber bands) to double use the sunlight by reflecting it back through the water again. The quantity produced might not be enough for the whole family but babies and younger children given preference could benefit best.

Cloudy Water

In cases where the water is initially cloudy or with much suspended particles it may be possible to use a small barrel or tub filled with gravel at the bottom (about 3 inches), then a layer of charcoal (about 2 inches), with fine sand on the top (as deep as possible to leave space for the water) to filter the water. The collection outlet for must be at the bottom to draw off the water, but it must also be looped upward to the above the level of the sand to stop the water draining off below the sand level and drying it out. After cleaning using this method, the sunlight method above could be used to add more protection as this filtration method is NOT as effective against bacteria.

Remember that although the sand will “ripen” for quite a while and improve its filtering capabilities, in time it will need to be changed for cleaning when it becomes ineffective, so it is advisable to have a full-width open top with a lid.


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For more detailed information refer to the sites above (and any others that you can find)

Prevention of water contamination

In areas of permanent human living, the separation of the disposal of human waste matter from sources of drinking water requires serious consideration from the outset if diseases are to be minimized. Consider if you really want all of your neighbor’s human waste buried in their plot drifting into your water source drawn from nearby. It is an unpleasant thought but a very real danger to the health and life, especially infants. So what is to be done about it? Consider forming a “clean water” committee to investigate the local conditions and what improvements could be made. Perhaps a special drinking water pump placed away from areas of housing and waste disposal.

In areas of very high-use, is it recommended that all waste be packed up and taken out to a properly designated disposal point. To make this easier, a “dry” toilet could be used in the form of a bucket with a handful of sawdust (or rice-hull) scattered in after use to keep down the flies and smell. Bury the human waste well away from existing residential sites and water sources (about 70 adult steps is recommended) to prevent site & source contamination, & reduce self contamination of the drinking water supply. This is especially difficult on shoreline sites where the natural flow of the underground water can be reversed twice per day by the rising and falling tide.