portable water purifier - better described as point of use ( POU ) water treatment system and field water disinfecting techniques - are self-contained units typically used by recreational enthusiasts, military personnel, survivors and people without access to water supply services in developing countries for water purification when they need to get drinking water from untreated sources (eg rivers, lakes, groundwater etc.). These tools and personal methods aim to make drinking water (ie safe and suitable for drinking purposes - without disease-causing pathogens).
Techniques include heat (including boiling), filtering, activated charcoal adsorption, chemical disinfection (eg chlorination, iodine, ozonation, etc.), ultraviolet purification (including SODIS), distillation (including solar distillation), and flocculation. Often these are used in combination. Many commercial portable water purification systems or chemical additives are available for hiking, camping, and other travel in remote areas.
Portable water purification methods are also commonly used at household level in developing countries when drinking water sources are not suitable for drinking (also called "water sources that are not recommended") - an approach called water self-sufficiency.
Video Portable water purification
The dangers of drinking water
Unprocessed water may contain potentially pathogenic agents, including protozoa, bacteria, viruses, and some high-level parasite larvae such as liver worms and roundworms. Chemical pollutants such as pesticides, heavy metals and synthetic organics may exist. Other components may affect taste, odor and general aesthetic qualities, including turbidity from soil or clay, the color of humic acid or microscopic algae, the smell of certain types of bacteria, especially Actinomycetes that produce geosmin, and saltiness of brackish water or seawater.
Common metal contaminants such as copper and lead can be treated by increasing the pH using soda ash or lime, which precipitates the metal. Careful logging of clear water after settlement or use of filtration provides acceptable low metal levels. Water contaminated by aluminum or zinc can not be treated in this way using strong alkali because higher pH dissolves metal salts. Salt is difficult to remove except by reverse osmosis or distillation.
Most portable treatment processes focus on mitigating human pathogens for safety and eliminating particulate substances, flavors and odors. Significant pathogens commonly found in developed countries include Giardia , Cryptosporidium , Shigella , hepatitis A virus, Escherichia coli , and enteroviruses. In developing countries there may be a risk of cholera and dysentery organisms and various tropical enteroparasites.
Giardia lamblia and Cryptosporidium spp. , both causing diarrhea (see giardiasis and cryptosporidiosis) are common pathogens. In the interior areas of the United States and Canada they are sometimes present in sufficient quantities that water treatment is justified for backpackers, although this has created some controversy. (See desert diarrhea.) In Hawaii and other tropical regions, Leptospira spp. is another possible problem.
Less common in developed countries are organisms such as Vibrio cholerae causing cholera and various Salmonella strains causing typhoid and para-thyroid disease. Pathogen viruses can also be found in water. The worm larvae are very dangerous in areas frequented by sheep, deer, or cattle. If these microscopic larvae are ingested, they can form potentially life-threatening cysts in the brain or liver. This risk extends to plants grown in or near water including commonly eaten watercress.
In general, more up-stream human activities (ie, the larger the rivers/streams) the greater the potential for contamination from waste, surface runoff, or industrial pollutants. Groundwater pollution can occur from human activities (eg sanitation systems or on-site mining) or may occur naturally (eg from arsenic in some areas of India and Bangladesh). Water collected as far as possible above all known or anticipated pollution risks has the lowest contamination risk and is best suited for portable treatment methods.
Maps Portable water purification
Technique
Not all techniques by themselves will reduce all the dangers. Although flocculation followed by screening has been suggested as best practice it is rarely possible without the ability to control pH and precipitation conditions carefully. Use of alum that is not recommended as flocculant may cause an unacceptable level of aluminum in the water so that it is treated. If water is to be stored, halogens provide more protection.
Hot (boiling)
Heat kills disease-causing microorganisms, with higher temperature and/or duration required for some pathogens. Water sterilization (killing all living contaminants) does not need to make water safe to drink; one just needs to make intestinal pathogens (intestines) harmless. Boiling does not remove most of the pollutants and leaves no residual protection.
WHO states bring boiling water then natural cooling enough to disable pathogenic bacteria, viruses and protozoa.
The CDC recommends boiling for 1 minute. At high altitude, the boiling point of water falls. At an altitude of more than 6,562 feet (2000 meters) of boiling should be continued for 3 minutes.
All pathogenic bacteria are quickly killed above 60 Ã, Â ° C (140 Ã, Â ° F), therefore, although there is no need to boil to make water safe to drink, the time it takes to heat water to boiling is usually enough to reduce the concentration of bacteria into the water. safe level. The complicated protozoa pathogen may require higher temperatures to eliminate any risk.
Boiling is not always necessary or sometimes sufficient. Pasteurization where enough killed pathogens usually occurs at 63Ã, Â ° C for 30 minutes or 72Ã, Â ° C for 15 seconds. Certain pathogens must be heated on boiling (eg Clostridium botulinum botulism requires 118Ã, Â ° C (244Ã, Â ° F), most endospores require 120Ã, Â ° C (248Ã, Â ° F), and higher prions.). Higher temperatures can be achieved with pressure cooker. The heat combined with ultraviolet (UV) light, such as the SODIS method, reduces the temperature and duration required.
Filtration
Portable pump filters are commercially available with ceramic filters that filter 5,000 to 50,000 liters per cartridge, moving the pathogens to a range of 0.2-0.3 micrometers (Âμm). Some also utilize active charcoal filtering. Most of these filters eliminate most of the bacteria and protozoa, such as Cryptosporidium and Giardia lamblia, but not viruses except the largest of 0.3 Ã,Âμm and larger diameter , so disinfection by chemicals or ultraviolet light is still needed after screening. It should be noted that not all bacteria are removed with a 0.2 Âμm pump filter; for example, thread strands like Spira. (which can cause leptospirosis) is thin enough to pass through the 0.2 Âμm filter. Effective chemical additives to overcome deficiencies in pump filters include chlorine, chlorine dioxide, iodine, and sodium hypochlorite (bleach). There have been ceramic polymers and filters on the market that combine post iodine treatment in their filter elements to kill viruses and smaller bacteria that can not be filtered, but most have disappeared due to unpleasant discomfort given to water, as well as adverse health effects when iodine is digested during prolonged periods.
While filtering elements can do an excellent job of removing most bacterial and fungal contaminants from drinking water when new, the elements themselves can become colonization sites. In recent years some filters have been enhanced by connecting silver metal nanoparticles to ceramic elements and/or activated charcoal to suppress the growth of pathogens.
Hand-pumped inverse osmosis filters were originally developed for the military in the late 1980s to be used as survival equipment, for example, to be supplied with an inflatable raft on an aircraft. Civil version available. Instead of using the static pressure of the water supply channel to force water through the filter, the pressure is given by the hand-operated pump, similar in function and appearance with a mechanical grease gun. This device can produce drinking water from seawater.
Portable Aqua Unit for Saving Lives (PAUL short) is a portable ultrafiltration-based membrane water filter for humanitarian aid. This allows decentralized water supply in emergency and disaster situations to about 400 people per unit per day. These filters are designed to work well with chemicals and energy or trained personnel.
Active adsorption charcoal
Granular activated granular filtration uses a form of activated carbon with a high surface area, and absorbs many compounds, including many toxic compounds. Water passing through activated carbon is commonly used in conjunction with hand-pumped filters to overcome organic contamination, taste, or unpleasant odors. Activated carbon filters are not usually used as a primary purification technique of portable water purification devices, but rather as a secondary means to complement other purification techniques. This is most often implemented for pre- or post-filtration, in a separate step rather than ceramic filtering, in case that is being carried out prior to the addition of a chemical disinfectant used to control bacteria or viruses that can not be removed by the filter. Activated charcoal removes chlorine from treated water, removes any residual protection in water that protects against pathogens, and should not, in general, be used without careful thought after chemical disinfection treatments in a portable water purification treatment. Ceramic Filters/Carbon Core with a pore size of 0.5 Âμm or smaller is excellent for removing bacteria and cysts while also eliminating chemicals.
Chemical disinfection with halogen
Chemical disinfection with halogens, especially chlorine and iodine, results from the oxidation of essential cell structures and enzymes. The main factors determining the rate and proportion of the killed microorganisms are the residual halogen concentrations available and the exposure time. Secondary factors are pathogenic species, water temperature, pH, and organic contaminants. In water disinfection, the use of 1-16 mg/L concentrations over 10-60 minutes is generally effective. Of note, Cryptosporidium oocysts, possibly Cyclospora species, Ascaris eggs are highly resistant to halogens and field inactivation may be impractical with bleach and iodine.
Iodine
Iodine used for water purification is generally added to water as a solution, in crystallized form, or in tablets containing tetraglycine hydroperiodide which releases 8 mg of iodine per tablet adaptation to chronic tetraglycine hydrouxide. Iodine kills many, but not all, of the most common pathogens present in natural freshwater sources. Bringing iodine to water purification is an imperfect but lightweight solution for those who need water purification. Kit is available in camping stores that include iodine pills and second pill (vitamin C or ascorbic acid) which will remove the iodine from water after being disinfected. The addition of vitamin C, in pill form or in aromatic drink powder, causes a lot of iodine out of the solution, so it should not be added until iodine has enough time to work. This time is 30 minutes in relatively clean warm water, but much longer if the water is cloudy or cold. Iodine drinking water, treated with tablets containing tetraglycine hydroperiodide, also reduces the absorption of radioactive iodine in human subjects only 2% of its value. This could be an important factor worth considering to treat water in the current post-nuclear event survival situation, where the consumption of radioactive iodine is a concern for internal radiotoxicity. If iodine has settled out of the solution, then drinking water has less iodine available in the solution. Also the amount of iodine in one tablet is not enough to block the taking. Tetraglycine hydroperiodide maintains its effectiveness indefinitely before the container is opened; Although some manufacturers advise against using tablets more than three months after the container is initially opened, the shelf life is actually very long as long as the container is resealed immediately after each opening.
Iodine should be allowed at least 30 minutes to kill Giardia.
iodine crystals
A lower cost alternative to using iodine based water purification tablets is the use of iodine crystals although there is a serious risk of acute iodine toxicity if preparation and dilution and not measured with some accuracy. This method may not be enough to kill the Giardia cysts in cold water. The advantage of using iodine crystals is that only a small amount of iodine is dissolved from the iodine crystals in each use, giving this method for treating water, the ability to treat enormous water volumes. Unlike tetraglycine hydroperiodide tablets, iodine crystals have unlimited shelf life as long as they are not exposed to air for long periods of time or stored under water. Iodine crystals will be sublimated if exposed to air for long periods of time. Large quantities of water that can be purified by low cost iodine crystals make this technique very cost effective for the point of use or an emergency water purification method intended to be used longer than the tetraglycine hydroperiodide shelf life.
Halazone Tablet
The previously popular chlorine-based halazone tablet is used for portable water purification. Chlorine in water is more than three times as effective as a disinfectant against Escherichia coli than iodine. Halazone tablets were thus commonly used during World War II by US troops for portable water purification, even included in the accessory package for Rations until 1945.
A major limitation of the halazone tablet is the very short lifetime of the opened bottle, usually 3 days or less, unlike an iodine-based tablet that has a lifespan of 3-month open bottles. Sodium dichloroisocyanurate (NaDCC) has replaced many of the halazone tablets for some of the remaining chlorine-based purification tablets available today. It is compressed with effervescent salts, usually adipic acid and sodium bicarbonate, to form fast dissolving tablets, diluted to 10 parts per million of available chlorine (ppm av.cl) when drinking water is contaminated lightly and 20ppm when it appears to be contaminated.
Chlorine bleach tablets provide a more stable platform for disinfecting water than liquid bleach (sodium hypochlorite) because the liquid version tends to decline with age and gives unregulated results unless testing is done - not practical on the spot. However, although chlorine-based halazon tablets fall out of favor for portable water purification, chlorine-based bleach may remain safe for short-term emergency water disinfection. Two drops of 5% unflavored bleach can be added per liter or liters of clear water, then left closed for 30 to 60 minutes. After this treatment, water may be left open to reduce the smell and taste of chlorine. Guides are available online for effective emergency use for bleach to create unsafe water. [1] [2]
Centers for Disease Control & amp; Prevention (CDC) and Population Services International (PSI) promote similar products (0.5% - 1.5% sodium hypochlorite solution) as part of their Safe Water Systems (SWS) strategy. The product is sold in developing countries under local brand name specifically for the purpose of disinfection of drinking water.
Bleach
Common bleach includes calcium hypochlorite (Ca [OCl] 2 ) and sodium hypochlorite (NaOCl) is an ordinary, well-researched, low-cost oxidation.
EPA recommends 2 drops of 8.25% sodium hypochlorite solution (usual, chlorine-free bleach) mixed per 1 liter/liter of water and let stand 30 minutes. 2 drops of 5% solution are also sufficient. Duplicate the amount of bleach if the water is cloudy, colorful, or very cold. After that, the water should have a little chlorine smell, otherwise repeat the dose and let stand for 15 minutes before use.
Both chlorine (eg, bleach) and iodine alone are considered fully effective against Cryptosporidium , although they are partially effective against Giardia . Chlorine is considered a little better against the last. A more complete field solution that includes chemical disinfectants is to first filter water, using a 0.2 Âμm ceramic ceramic filter pump, followed by treatment with iodine or chlorine, thus filtering out cryptosporidium, Giardia and most of the bacteria, together with the virus greater than. , while also using chemical disinfectants to deal with viruses and smaller bacteria that can not be removed by the filter. This combination is also potentially more effective in some cases than using portable electronic disinfection based on UV treatment.
Chlorine dioxide
Chlorine dioxide can be derived from tablets or made by mixing two chemicals together. This is more effective than iodine or chlorine to giardia, and although it has only low to moderate effectiveness against cryptosporidium, iodine and chlorine are not effective against these protozoa. The cost of chlorine dioxide treatment is higher than the cost of iodine treatment.
Mixed oxidant (MiOx)
The salt water in electrolytic reaction produces strong mixed oxidant disinfectants (mostly chlorine in the form of hypochlorite acid (HOCl) and some peroxides, ozone, chlorine dioxide) to inactivate viruses, bacteria, Giardia and Cryptosporidium killing 99.9% of all organisms without the need to filter. MiOx is considered stronger than chlorine.
Khlor Tablet (NaDCC)
Sodium dichloroisocyanurate or Troclosene Sodium more commonly abbreviated as NaDCC, is a form of chlorine used for disinfection. It is used by all the major NGOs such as UNICEF to handle water in emergencies, and extensively by social marketing organizations for household water treatment where household water sources may be unsafe.
The NaDCC tablets are available in various concentrations to treat various water volumes to provide 5% of the chlorine recommended by the World Health Organization. They are effervescent tablets that allow tablets to dissolve in minutes.
Other chemical disinfection additives
Silver ion tablets
An alternative to iodine-based preparation in some usage scenarios is the tablet or droplet of ionic/chlorine dioxide. This solution can disinfect water more effectively than iodine-based techniques while leaving virtually no real flavor in water in some usage scenarios. A silver/chlorine dioxide based ion disinfectant agent will kill Cryptosporidium and Giardia , if used correctly. The main disadvantage of the silver/chlorine dioxide ion technique is the long purification time (generally 30 minutes to 4 hours, depending on the formulation used). Another concern is the possibility of deposition and accumulation of silver compounds in various body tissues leading to a rare condition called argyria that produces permanent pigmentation, staining, bluish gray on the skin, eyes, and mucous membranes.
Hydrogen peroxide
One recent study found that wild Salmonella that will reproduce rapidly during subsequent dark storage of solar disinfected water can be controlled by the addition of only 10 parts per million of hydrogen peroxide.
Ultraviolet purification
Ultraviolet (UV) light induces the formation of covalent bonds in DNA and thus prevents microbes from multiplying. Without reproduction, microbes become much more dangerous. UV-C germs of light in the short wavelength range 100-280 nm act on thymine, one of the four basic nucleotides in DNA. When UV photons of germs are absorbed by a thymine molecule adjacent to other thymine in a DNA strand, covalent bonds or dimers between molecules are made. This thymine dimer prevents the enzyme from "reading" DNA and copying it, thus castrating microbes. Prolonged exposure to ionizing radiation can lead to single and double bond breaks in DNA, membrane lipid oxidation, and protein denaturation, all toxic to cells. However, there are limitations to this technology. Water turbidity (ie, the amount of suspended solids and colloidal solids contained in water to be treated) should be low, so the water is clear, for UV purification to work properly - so pre-screening steps may be necessary.
The concern with UV portable water purification is that some pathogens are hundreds of times more sensitive to UV light than others. Protozoal cysts were once believed to be the most sensitive, but recent studies have proven otherwise, suggesting that both Cryptosporidium and Giardia are disabled by UV doses of only 6 mJ/cm 2 However, EPA regulations and other studies suggest that the virus is limiting factor of UV treatment, requiring UV light dose 10-30 times greater than Giardia or Cryptosporidium . Studies have shown that UV doses at levels provided by a common portable UV unit are effective for killing Giardia and that there is no evidence of cyst repair and reactivation.
UV-treated water still has microbes in the water, only by means of reproduction they turn "dead". In the case of UV treated water containing castrated microbes exposed to visible light (specifically, light wavelengths greater than 330-500 m) for any significant period of time, a process known as photo reactivation may occur, where the possibility of repairing damage to DNA reproduction of the emerging bacteria, potentially making them once again capable of reproducing and causing illness. UV-treated water should not be exposed to visible light for any significant period of time after UV treatment, before consumption, to avoid ingesting re-activated and harmful microbes.
The latest developments in semiconductor technology enable the development of UV-C Light Emitting Diodes (LEDs). The LED UV-C system overcomes the disadvantages of mercury-based technologies, namely: power-cycling penalties, high power requirements, friability, heating time, and mercury content.
Ozone water disinfection
In the disinfection of ozone water, microbes are destroyed by ozone gas (O 3 ) supplied by an ozone generator. Common in Europe, ozone gas is now becoming widely adopted in the United States. It appears in various industries; from municipal water treatment plants, to food processing plants, to health care organizations. It was adopted because of its ability to clean water and surface without wasting water, and because there are no byproducts. When the work is done, the ozone gas quickly degrades into oxygen. Ozone is more effective than chlorine in destroying viruses and bacteria.
In 1990, the Organic Food Production Act (OFPA) identified aqueous ozone as a permitted substance for use in the production of organic crops and livestock. In 1997, it was approved by the FDA as an antimicrobial agent for use on food. In 2002, the FDA approved ozone for use in food contact areas and directly on foods with general determination. Considered as Safe ("GRAS").
Ozone is most often made by a process called "corona release", which causes oxygen molecules (O 2 ) to temporarily rejoin ozone (O 3 ). This gas is very unstable, and the 3rd oxygen molecule reacts with pathogens by penetrating the cell wall of bacteria and viruses. It destroys the organism.
Ozone is effective against pollutants for the same reason; it will react with long-chain (organic) carbon molecules, and break them down into less complex (and usually less harmful) molecules through oxidation.
Advances in ozone generation techniques, coupled with filtering, make it a viable new portable water purification method.
Solar water disinfection
In solar water disinfection (SODIS), microbes are destroyed by the temperature and UVA radiation provided by the sun. Water is placed in a transparent PET plastic bottle or plastic bag, oxygenated by shaking some of the bottle filled to the brim before filling the bottle along the way, and left in the sun for 6-24 hours above the reflective surface.
Solar distillation
Solar distillation depends on sunlight to warm and evaporate water for purification which then condenses and drips into the container. In theory, the sun (condensation) still removes all pathogens, salts, metals, and most chemicals but in field practice the lack of clean components, easy contact with dirt, improvised construction, and disturbance of clean, but contaminated water.
Homemade water filter
Water filters can be made in place using local materials such as sand and charcoal (eg from firewood burned in a special way). This filter is sometimes used by soldiers and outside fans. Because of their low cost they can be made and used by anyone. The reliability of such systems varies greatly. Such filters can do little, if any, to reduce germs and other hazardous substances and can give the false sense that the water produced can be drunk. Water processed through an improvised filter should undergo secondary processing such as boiling to make it safe for consumption.
Prevention of water contamination
Water-borne human diseases usually come from other humans, so the material from humans (dirt, medical waste, wash water, grass chemicals, gasoline engines, garbage, etc.) should be kept away from water sources. For example, human waste must be buried deep (& gt; 60 meters/200 feet) from water sources to reduce contamination. In some jungle areas, it is recommended that all waste be packed and transported to properly designated disposal sites.
See also
- Ceramic water filter
- Desalination
- Water supply and sanitation itself
- Diarrhea Traveler
- Water quality
- Wilderness gets diarrhea
References
External links
- Knowledge of Household Water Treatment on CAWST's website
Source of the article : Wikipedia
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