1) In general free chlorine (HOCl) is five times more viricidal and four times more cysticidal than hypo iodous acid (HIO), and is two hundred times more viricidal and two times more cysticidal than I2 (George Clifford White, p. 1378). However, iodine can be effective against Giardia when properly applied. Iodine and chlorine tablets without filtration could pass EPA Purifier Protocols for Type I and Type II waters if only Giardia is tested, but not if Cryptosporidium is tested.
2) The UV Steri-Pen does not work well in turbid waters or in water containing naturally-occuring humic acids because UV is absorbed by humic acids. In addition, adeno-viruses are more resistant to inactivation by UV than are bacteria or protozoan cysts and oocysts. The Steri-Pen has passed EPA Purifier Protocols for Type I water, but not for Type II water without first filtering. (The MSR MIOX Purifier does not require pre-filtering to meet purifier standards.) The humic acids and turbidity in Type II water cloud and absorb the light, decreasing UV transmission, and allowing more nucleation points for clumping.
3) Iodine and chlorine technologies will leave a residual, but both disinfectants are ineffective against Cryptosporidium.
4) Use of filters without a viral guard is not recommended for standing water, due to the potential for virus contamination.
5) The MSR MIOX Purifier will not filter particles out of the water, although it will make even turbid water safe to drink without filtering. If the user is concerned about aesthetic quality of the water, there are various methods for removing solids, including filtering the water, passing it through a fabric cloth, or using a pinch of powdered alum.
6) The required quantity of any tablet disinfectant is compact for low-volume use. However, if a longer trip is planned, the number of tablets required in bulk may exceed the size of a treatment “device.” For example, one ClO2 tablet treats 1 L of water. The MSR MIOX Purifier treats ~200 L on one set of batteries.
7) The purifier is 7 times smaller than a standard filter and ¼ the weight.
8) Filters must be scrubbed periodically to remove captured particulates that can clog the filter pores.
9) UV is notorious for the outside surface of the lamp fouling with both organic and inorganic material. Large-scale UV systems have self-cleaning apparatus in place to remove this biofouling. It can be assumed that the UV Steri-Pen would also need to be cleaned periodically to keep functioning.
10) Although filters are generally fairly rugged, ceramic cartridges are susceptible to cracking if dropped.
11) Any tablet disinfectant will have submersibility and shelf life issues.
12) A sufficient quantity of iodine and chlorine tablets could treat large quantities of water in a fairly short period of time. However, tablets are designed for smaller treatment quantities. The more water the user plans to treat, the more tablets would be required. The UV Steri-Pen was also designed with smaller treatment capacities in mind, with a single dose intended for only ½ L. The MSR MIOX Purifier has single dosage quantities designed for ½ L up to 4 liters (approximately 1 gallon), and can treat multiple containers of water at the same time.
13) EFFICACY & TIME REQUIRED:
Filters alone will not remove viruses.
The standard waiting time for both chlorine and iodine tablets, as advised by emergency response groups, is 30 minutes, but these technologies will not inactivate Cryptosporidium without filtration. Katadyn recommends a dwell time of 30 minutes with use of their chlorine tablets but recommends 4 hours for more resistant organisms such as Giardia.
ClO2 tablets require 15 minutes for bacteria and viruses and 4 hours to inactivate Giardia and Cryptosporidium.
The UV Steri-Pen is effective against all classes of organisms in clear water but against nothing in turbid water.
The MSR MIOX Purifier requires 15 minutes for viruses and bacteria, 30 minutes for Giardia, and 4 hours for Cryptosporidium, and the quality of the source water is irrelevant. Potability of water can be guaranteed with the MSR MIOX Purifier’s safety indicator, which cannot be used with any other technology.
Time Required (minutes) for Removal of
Bacteria, Viruses, & Giardia, and
Simultaneous Treatment of Various Volumes
14) The UV Steri-Pen requires four AA batteries, which are readily available, but the bulb will wear out after treatment of 625 gallons of water, according to the manufacturer. A Steri-Pen with a broken or exhausted bulb must be returned to the factory for installation of a new bulb. In contrast, salt and lithium camera batteries for the MIOX purifier are readily available worldwide and can be installed by the user.
15) Bottled iodine tablets have a shelf life of 5 years if the bottle is unopened. However, once the bottle is opened, shelf life is only 6 months. Iodine crystals have no shelf life.The shelf life for chlorine tablets is in the range of several years if stored properly (cool, dry, no light). High temperatures, sunlight, and humidity can have a dramatic effect on decreasing shelf life, even to within only a few weeks of viability.
16) The MSR MIOX Purifier is the only water purification option supplied with a purity indicator and calibrated to match proper usage only with the purifier. Other treatment technologies have no way of guaranteeing the water is safe to drink.
17) LIFECYCLE COSTS:
Filters range from $25 up to $800. Replacement cartridges for various filter types range from $40 to $200. The MSR MiniWorks EX filter is the market leader and sells for ~$80 with a replacement filter costing $35. Manufacturer’s instructions indicate that filters must typically be replaced every 2,000 liters. If treating highly turbid water, filter cartridges may need to be replaced much sooner.
Potable Aqua iodine tablets sell for about $5 per bottle, contain 50 tablets per bottle, and require 2 tablets per liter.
Katadyn chlorine tablets sell for $14 for 30 tablets, and 1 tablet is required per liter.
Micropur ClO2 tablets sell for $14 for 30 tablets, and 1 tablet is required per liter.
The UV Steri-Pen retails for ~$150. Testing indicates ~25 treatments of ½ liter each before battery replacement is required, when using 4 disposable AA alkaline batteries. Four AA batteries retail for $2.67. Manufacturer’s instructions indicate that bulb replacement is required after ~625 gallons of treatment. To replace the bulb, the Steri-Pen must be returned to the factory for a charge of $60.
The MSR MIOX Purifier retails for $129.95 and will treat 200 L before batteries must be replaced. Two lithium CR123 batteries retail for $3.50 on-line. The more you utilize the purifier, the more economical it becomes in contrast to tablets, which are totally consumed with each application, and must therefore be replaced in full.
Total Cost (Initial Purchase & Replacement Parts)
for Various Volumes on Clean Water
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发表于 2007-2-18 22:01
