What is the best way to filter water at home?
1) How can I purify my water without a filter?
The cheapest way to filter water methods presented in this sheet make it possible to make the water drinkable. They can be applied at home, on a family scale.
Is about :
Treating water before drinking helps fight many diseases such as dysentery, typhoid and cholera.
3) Filtration By Fabrics
The water can be filtered easily with the help of a cloth. Doing so allows you to remove the main solid impurities from the water, as well as the insect larvae it may contain. The fabric used, preferably cotton, should be thick enough to retain impurities. If it is too thick, the filtration will last longer. It must be washed before each use.
By itself, filtration is not a satisfactory means of treatment. However, filtering the water before treating it with any of the other methods mentioned in this sheet allows to significantly improve the quality of the water obtained.
– Ease of application.
– Almost zero cost.
– Very useful, and even essential for pre-treatment.
– Shallow treatment unable to provide drinking water if the water is contaminated at source.
4) The Three-Pot Method
It fulfills the same role as filtration, and allows the main solid impurities of the water to be separated.
To increase its efficiency, this method can be used as a complement to filtration.
– Ease of application. Virtually zero cost.
– Significant reduction of impurities and pathogenic germs.
– The disinfection is not total.
– Wait time.
5) Treatment By Boiling
The application of the boiling treatment is also relatively simple. It allows to kill all the germs and microorganisms present in the water. To do this, it must be filtered or decanted beforehand and then boiled in large quantities (it is not enough to bring it to a boil) for one minute at low altitudes and for three minutes at more than 2,000 meters. Boil-treated water may taste bland. This problem can be solved by shaking it vigorously to reoxygenate it or by adding a little salt.
– Ease of application.
– Kill all pathogenic germs.
– You need wood (about 1 kg per liter of water) and a heat resistant container.
6) Chlorination Treatment
(For more precise information, see Sheet E18, “Water treatment by chlorination” ).
Chlorination is a simple and effective means of disinfecting water and making it drinkable. It consists of introducing chlorinated products (chlorine tablets, bleach, etc.) into the water to kill the microorganisms contained therein. After an action time of about 30 minutes, the water becomes drinkable. Thanks to the residual effect of chlorine, it continues to be so for a few days (depending on storage conditions).
– Muddy water can be made drinkable. If the treatment is done correctly, all pathogenic germs are eliminated.
– Long-lasting effect of chlorination.
– In most cases, the products must be transported from abroad. Risks derived from its manipulation.
– Not inconsiderable cost.
If necessary, this chlorination can be carried out after flocculation, in a terracotta vessel fitted with a tap at the bottom (the drinking water station imagined by Dr. Monjour; see the end of the document) or another container.
7) Treatment By Sand Filtration
(For more precise information, see Sheet E21, “Treatment of water by slow filtration in sand for family use” ).
The sand filter is an environmentally friendly, relatively simple and inexpensive water treatment method. Its principle consists in making the water percolate through a layer of sand. There are two types :
A) The Pretreatment Sand Filter
It fulfills the same role as fabric filtration. In general, it is more efficient, and has the same advantages and disadvantages.
– Ease of application. Low cost.
– Adapted to emergency situations.
– It only allows a superficial treatment of the water.
– It is only effective as a pretreatment for disinfection methods by solar radiation, chlorination or boiling.
B) The Biological Sand Filter
This filter constitutes a filtration and decontamination medium in itself.
– With proper maintenance, the biological sand filter is effective for a long time. Cheap.
– Treatment can be slow.
– More complex maintenance and control.
8) Treatment By Ceramic Filter
(For more precise information, see Sheet E22, “Treatment with ceramic filters” ).
Ceramic filters for water treatment have been used for several centuries.
Depending on the type, they can be small fixed installations (individual) or portable devices that allow water to be filtered anywhere.
These kits can be supplied by manufacturers of water purification systems and products.
In developing countries, filters are manufactured locally, often by self-financed micro-enterprises. They are usually in the shape of a pot or jar, and are impregnated with fine colloidal silver particles that act as a disinfectant and prevent the growth of bacteria. The filter is installed in a container of between 20 and 30 liters of capacity, made of plastic or ceramic.
If properly designed and manufactured, these devices can kill or inactivate nearly all protozoan bacteria and parasites . In contrast, they are not effective against viruses . Cleaning and maintaining the filter is very important: an educational program on safe storage techniques, filter cleaning, and other recommended actions is recommended.
– Easy to use.
– Long operating life.
– Quite low cost when the filter is manufactured locally.
– Low production flow (1 to 2 liters per hour).
– Potential risk of recontamination of conserved water without residual chlorine.
– Filter maintenance necessary (with a brush for cleaning).
9) The Sodis Method
(For more precise information, see Sheet E19, “Treatment by Sun Exposure. The SODIS and Solvatten Methods ).
The SODIS method is perfect for treating drinking water in developing countries, since it only needs sunlight and light transparent plastic bottles: the so-called PET (polyethylene terephthalate).
The clear PET bottles are filled with water and exposed to the sun for six hours. The UVA rays contained in sunlight kill infectious germs, such as viruses, bacteria and parasites (Giardia and Cryptosporidia). This method also works when air and water temperatures are low.
– Ease of application.
– Zero cost.
– Efficiency, reliability.
– Treatment duration.
– Low volume treated.
10) The Solvatten Procedure
(For more precise information, see Sheet E19, “Treatment by exposure to the sun. The SODIS and Solvatten methods” ).
The Solvatten method has been developed by the Swedish organization of the same name. It is an ingenious adaptation of the SODIS method. It uses a special drum that is filled with water (previously filtered or decanted if it is in bad condition) and is exposed to the sun. After a period of between two and six hours, depending on the weather conditions, a red pill in the device turns green, indicating the end of the treatment. The water can be allowed to cool so that the consumer can consume it, or used as it is, already hot, to cook food.
The Solvatten method combines filtration and disinfection by UV and heating. It is very effective.
– Ease of application.
– Efficient and reliable method. Comfortable and reassuring use for people on the go.
– Drums must be purchased in Sweden and transported from there.
– High cost for families with few resources (70 euros when leaving the factory for pallets of 72 units).
– Water not protected against recontamination if it is not drunk quickly enough.
11) The Lifestraw Method Or The “Filter Straw”
This method, invented fairly recently by Vestergaard Frandsen, a Danish man who markets the procedure through a Swiss company of the same name based in Lausanne and with 11 continental or regional offices, is particularly straightforward.
It consists of sucking the water, but not through a straw, but a small plastic tube of 3 cm in diameter and 25 cm in length that contains disinfectant filters, mainly based on the use of activated carbon and iodized products (which should reduced by the taste it sometimes gives to water).
This device, whose cost (in large quantities) is about 3 euros (sometimes more) should allow the filtration of 700 to 1,000 liters of water.
The company, specialized in products for emergencies or prevention of certain diseases, has also created what it calls the “Lifestraw Family”, a device that adapts the previous principle to the use of a whole family and is capable of filtering between 15,000 and 18,000 liters of Water.
– Simplicity, very simple maintenance (blowing towards the device to avoid obstructions).
– Great comfort in case of displacement or failure in the water treatment system.
– Elimination, allegedly almost complete, of bacteria and protozoan parasites.
– It doesn’t need any energy.
– Reduction of turbidity (possible use of water in poor condition) by filtering particles down to 0.2 microns.
– Product especially suitable for emergency or temporary situations.
– Low cost, but still very high for the many regions where income does not exceed one euro per day, and compared to the average cost of a simple and definitive supply of drinking water (from 20 to 30 euros per person).
12) The Methods Of Purification By Generation Of Ultraviolet Rays
(For more precise information, see Sheet E20, “Water treatment by the combined use of solar energy and ultraviolet rays” ).
A) The NEDAP Method
It has been developed by the Dutch company NEDAP, which has designed a small volume, mobile device weighing 75 kg called “Naiade” .
The procedure consists of disinfecting the water after its filtration with the help of an ultraviolet lamp . The lamp is powered by a solar panel.
After filling the tank, the water passes through 3 filters, which successively retain gravel, suspended materials and particles. The UV lamp heats up in two minutes and emits UV rays that disinfect the water at a rate of 4-5 liters per minute. It can purify up to 2,500 liters of water in ten hours.
The factory price of the Naiade is at least 4,000 euros. For a useful life of ten years, in a village of 250 inhabitants, it represents an investment of 2 euro cents a day for 20 liters of water for each inhabitant. This rate includes depreciation, use and maintenance. However, including the installation, its price can reach 6,000 euros.
– Ease of application.
– Low maintenance cost after purchasing the equipment.
– Efficiency and speed.
– Good daily production capacity (up to 2,500 liters of drinking water).
– The material must be imported. Important purchase cost (at least 4,000 euros).
– Water not protected against contamination if it is not used quickly enough.
B) The Concept “1,001 Sources”
It was born in Cambodia in 2004, and was designed by the French NGO of the same name. Its objective is to supply drinking water to people or villages that lack it, while creating a small local economic activity through the sale of water produced at a low price, but enough to remunerate those responsible for its exploitation and allow its developing. The technique is practically identical to the previous one. The device, called Fontaine (font in French) and not very bulky, is made up of 4 filters and an ultraviolet lamp powered by electricity through a solar panel. Before being introduced into the filters, the suspended materials are removed from the water by decanting it into 2 large tanks adjacent. It then passes successively through 4 increasingly fine filters and is exposed to radiation from the UV lamp, which kills or inhibits bacteria.