My husband and I are interested in clean-water technologies for coastal disaster relief. Using on-site materials when possible. I would love to hear about other methods.
The sand filter is a great basic technology, thanks for sharing the diagram.
The PET bottle-in-the-sun method (SOL-whatsis) is also very useful for equatorial regions. There are worse things than water has been sterilized in warm, food-grade plastic; yuppies pay a lot for PET-contaminated water. And the solar process does seem to kill off most pathogens in clear water.
Narrowing down the discussion:
Alessandro, there are a LOT of ways to filter or sterilize water. All are interesting, and some are useful. But if you want GOOD ideas, you need to know what situation they should be good FOR. (purpose). In a specific situation, one method may be better than another.
These forums mostly involve two kinds of situations:
1)
Appropriate technology for home use, such as farms and urban eco-homesteads; and
2) Appropriate technology for low-impact or primitive use, such as for the third world, outdoor survival, or disaster relief.
We are happy to think about other situations whenever someone describes them.
For coastal disaster relief, we have been looking for portable methods, and methods that can be copied using
local materials. We have lived and camped in 'primitive' wilderness areas in North America and elsewhere. We carry our own water purification, and/or use systems set up and maintained by locals, such as sand filters and
wells. So these are the situations I think about for 'free' or 'affordable' water purification.
Regarding your question about UV patents: I don't know what variations of UV technology are patented. In the US or elsewhere. But the patent should not stop you from re-inventing something for personal use. It is rare to have problems with patent infringement unless a person is publishing or selling patented technology.
* * *
Regarding "Free" technologies:
Clean water is rarely free. There is always a cost in time, money, or materials.
The question is, how clean do you want the water, and what are your resources?
Charcoal, sand, PET bottles, terra-cotta,
concrete: available in most places, but not free everywhere.
How bad is the water to begin with? Salt, fertilizer,
petroleum; giardia, cholera, typhoid; rain or drought; donkey
poop or bird guano; or what? Sometimes filtration is enough, other times distillation or boiling won't even remove industrial wastes.
In places where wealthy nations have sponsored a new well for 'free' water access, there have been problems with finding replacement parts when the seals or pumps wear out, or accessing the parts for maintenance with limited tools.
Charging a small amount for each gallon of water (like 3 cents) can be enough to allow the village to replace those parts, or even send someone to school to learn how to maintain the well. Likewise, when people pay for a personal water filter, such as a ceramic or sand filter, they are often more likely to maintain it than if it was given for free. Working or paying for something, in many cultures, indicates that it has value. Free things may not be valued.
Time is also valuable. If a person is too poor to buy clean water, or to maintain a clean well, they are likely to be busy with the work of survival. Not likely to have spare time for education, research, or extra chores. It is important to consider what locals value enough to spend time on, and what options they would accept. Children's health is often a starting point for discussing community needs.
So if you want 'free' methods, are you specifically looking for short-term solutions that will be used and discarded by refugees or campers?
Or are you looking for a method that can be reproduced locally, using local materials, without imported parts? Local methods often cost more, in time and effort, than purchased methods. But they can be more resilient when economies shift.
I suggest considering 'nearly free' or 'affordable' options as well as 'free' ones.
* * *
Water sources and purification methods:
Salt water can be purified by solar distillation, or reverse-osmosis filtration, among other methods. These may also work on river water contaminated by farm pollution, or some kinds of industrial pollution.
Fresh water:
Distilled:
Rainwater and distilled water are basically pure already. The trick is collecting them without also collecting bird poop, mold, or other contaminants. Several rural friends drink local rainwater without any treatment. They gather it from a clean roof in large bottles, which are replaced every day or two. The roof is cleaned and inspected a few times per season. As long as the collection area stays clean, this works OK. They are still alert for sickness and drink a lot of boiled tea, but use rainwater for dishes, teeth cleaning, and in small amounts for drinking.
In low-rainfall areas, solar distillation methods can collect water from earth or plant matter, and this distilled water can be used (when fresh) without further treatment.
Most well water can be used with basic filtration, as long as the well is protected from livestock and sewage leaks.
Ice and snow are mostly pure; even sea-ice will (over time) purify itself from the top down. Freezing the water and thawing it again kills many pathogens, but takes a lot of energy. Some areas have frozen water available when fresh water is scarce.
Stagnant water:
Water that is saved in a cistern is stagnant (standing still) and likely to breed contamination. No matter how clean, stagnant water should not be trusted. Boil or disinfect before drinking. I have seen clean (previously chlorinated, filtered) tap water, in a clean glass, in the fridge, grow fungal snowballs and black mold colonies, when left long enough.
Running (Aerated) water is generally cleaner than stagnant water. Aeration can help keep water fresh longer. In the wild, running streams are cleaner than stagnant lakes.
But any open water source can be contaminated by unseen problems upstream (a dead animal, fecal matter from ignorant campers or livestock, sewage from upstream villages, fertilizer and pesticide runoff, etc).
Many places in the world collect water directly from rivers or open water sources; ANY filtration method is an improvement. Even filtering through 4 layers of an old cotton sari will remove a large proportion of cholera and other large parasites. Water will not be 'clean,' but 'cleaner' than it was. (Research over 10 years old, for use in India.)
Filtration:
For water filtration in special situations, many commercial tools are available to make water safe. Chemical, charcoal, ceramic, and reverse-osmosis filters are available for home systems and in bottles for camping. These cost different amounts, and some last longer while others need frequent replacement.
Filters that stay damp collect biological activity. Sand filters use this to improve filtration; charcoal and commercial filters may become less effective once biological activity begins. Bioremediation can also be used to help decontaminate local groundwater and creeks;
Paul Stamets lists
mushrooms that concentrate or break down things like petroleum and heavy metals.
Boiling water is an ancient method of sterilization. Tea-drinking is a healthy part of many cultures, and sometimes becomes a sacred or high-culture
art form: it ritualizes the boiling of water for drinking, protecting its practitioners from dehydration and water-borne diseases. Tea-stoves and solar cookers can boil water with minimal or no fuel.
If I am camping or building a primitive
shelter on unimproved land, I look for running water from a spring, and then use the easiest available method to sterilize, such as boiling. (Where I live, there is plenty of water, and plenty of
wood.)
I prefer boiling over adding iodine or chlorine; water can almost always be boiled using locally available materials. If I have to use tablets, iodine might be more nutritious than chlorine in dry inland areas. I personally prefer boiling to PET sterilization. Plus, I like tea.
Adding alcohol can also inhibit bacterial growth. I don't know what concentration is considered sterile. We used 4% alcohol to preserve bio-extracts in a laboratory setting. 4% is about the same concentration as the European 'small beer' that was served to women and children in the Middle Ages.
Tuscans still drink wine and water together, mixed to each person's desired concentration at the table, and this is not considered primitive (except possibly by the French).
Please let me know of any other methods you find interesting or useful.
Yours,
Erica Wisner
www.ErnieAndErica.info
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