There is nothing worse than getting sick while out walking, and one cause is contaminated water. A big problem is you very often do not know whether the water in front of you is safe or not. There may be ‘bugs’ in the water: very small viruses, middle-sized bacteria or largish protozoa. There are four common ways used to convert water of doubtful quality into something you can safely drink – or to make those bugs harmless.
- Boiling – takes a lot of time and fuel, leaves water hot or tasting ‘flat’
- Filtering – does not take out the very small viruses
- Chemicals – do not always work reliably, may take hours to be effective 1
- UV light – as reviewed here
Boiling, though it consumes fuel and time, is very effective if you do it as part of cooking. Filters can be heavy, have limited filter life and with one exception filters do not remove viruses. Since those little rotaviruses (for example) are responsible for a lot of dysentery, it is unfortunate that filters let them through. There are a lot of different chemicals on the market for treating water, including iodine, chlorine and chlorine dioxide, but they all have the serious problems of residual smell and taste. In addition some by-products of these chemicals are not very nice.
The chemicals do work quite well against most viruses and bacteria and are very widely used for this purpose. However, their efficacy against protozoans (such as Giardia lamblia and Cryptospordium spp.) in cyst form2 is questionable within the short contact times suggested by most manufacturers (< 30 minutes). This is because protozoa have a very hard shell around them a lot of the time. This concern has been validated in the United States during the failure of various chlorine-disinfection facilities in water distribution systems, with protozooan outbreaks as a result of short contact times. The risk of outbreaks in Europe has decreased dramatically in recent years, and this may result from increased efficacy of chlorine dioxide against protozooans in cyst form. Unfortunately, little research has been performed to understand why chlorine dioxide may be more efficacious against cysts. Early findings suggest that, unlike chlorine or iodine, chlorine dioxide's molecular structure is able to permeate the cyst wall without becoming inactivated.
Lacking a quick, perfectly effective chemical treatment, we are left with UV light, which has been used to deal with ‘bugs’ and purify water as far back as 1910. It has been used commercially for applications such as bottling plants and extensively for chemical-free community water supplies, and its popularity is increasing. However, you should note that UV treatment has no effect on any chemicals which might be in the water – especially nasties like agro-chemicals, solvents and so on. You will need to watch where you get your water from – but you’re probably doing that already.
- Effortless operation
- Lighter than any filter
- Works for all bugs to EPA standards
- Treats 1 litre (1 quart) in 90 seconds
- No chemical smells or residuals
- Can use rechargeable batteries
What’s Not So Good
- It isn’t cheap
- It relies on batteries, which it loads very heavily
- Batteries are a little expensive (but cheaper than most filter cartridges)
- I worry about breaking the quartz lamp cover
- Solar Charger is a bit heavy – an overkill design
|2006 SteriPEN Adventurer|
SteriPEN Adventurer Case
|254 nm, in the deep UV-C range|
|Negligible through common plastics and glass|
|Embedded microprocessor with safety interlocks|
Estimated battery life
|About 60 L (60 qt) for 2 non-rechargeable cells in warm weather|
Solar Cell Area
|130 x 55 mm (5 x 2.2 in)|
|US$129.95 for SteriPEN Adventurer; US$49.95 for the solar charger|
A serious caution should be given here as this whole area of water treatment or purification is a minefield. Each vendor of a purification product will present a threatening analysis of the water problem and a glowing analysis of the effectiveness of the product he or she is selling. Unfortunately, while the sales pitches may be fairly truthful they are not always complete. I have found that the bits which get glossed over or left out are sometimes rather critical. Well, I guess no manufacturer wants to tell you the bad bits. Also, there is a specialised jargon involved, as discussed below. It can all be very confusing.
However, I am also aware that some products on the market are relatively ineffectual, and others use a lot of ‘weasel words’ in their claims. The manager of AccuFilter went too far and ended up in jail in 1996 for fraud after being prosecuted by the EPA for the second time. On the other hand, the information provided with the SteriPEN Adventurer seems complete and credible.
In real life many walkers never bother treating their water: they are just careful where they get it from – and they survive. If you combine this caution with the UV treatment, you should be doing well.
Method of SteriPEN Operation
Each photon of UV light contains some energy, and if the wavelength of the UV light is short enough the energy can be sufficient to cause a change somewhere in the chemical bonds inside the bugs. For instance, if the bug has DNA, the UV light can cause the thymine bases in the DNA to lock up with each other, which prevents the bugs from replicating (breeding). In general, if the bugs can’t breed and multiply inside you, they can’t do you any harm. Of course, you need fairly energetic photons for this, but light in the UV-C band can do this. A common source of this is a discharge lamp emitting at 254 nanometres (nm), although some fluorescent lamps can also be used. The EPA has a lengthy document 3 on the whole subject, although it is primarily focused on industrial-sized systems.
Large discharge lamps with adequate power came first; very small ones with enough power were developed only more recently. The SteriPEN uses one such small UV-C lamp, which looks very similar to the Philips TUV4T5 Germicidal Sterilamp used in the Aquastar product. The SteriPEN Adventurer uses a microprocessor to control the operation and is powered by two CR123 (photo) lithium batteries. The company claims the lamp will provide at least 9,000 effective doses of UV but to be on the safe side they have limited the operation to 5,000 doses, and the unit gives a warning when you have passed 4,900 doses. They can replace the lamp. I would add that 5,000 doses is a lot of water treated.
Effectiveness of UV-C light and the SteriPEN Adventurer
It’s no use taking something which is not going to work. Those home-made gravity-powered filters using a plug of cotton wool may be very light and very cheap, but they are not going to stop any viruses, nor any bacteria, and probably won’t stop protozoa. They might make the water look clean and give you a happy feeling, but that feeling might change to unhappiness a day later if you get dysentery. There are EPA standards for water purification which are designed to protect your health, and it is wise to use a purification method which meets those standards. In passing, you should note that while many filters meet the EPA standards for protozoa and bacteria they do not normally meet the standard for viruses. Only a product which meets the EPA standards for all three sorts of bugs can qualify as a ‘purifier’: the use of the word is legally restricted in this context.
It has long been known that UV light can disable viruses and bacteria. Up until recently it was thought that UV light could not kill protozoa, but in the 90s it was found that researchers were asking the wrong question. UV light does not ‘kill’ the protozoa, but it does stop them from reproducing inside your gut, and as explained above if they can’t breed they can’t hurt you. Once this was understood the popularity of UV-C treatment for community water treatment started to rise. However, some non-UV water-purification companies still do not even acknowledge UV treatment as an option.
While this may be getting a shade esoteric, field tests have shown that our waterways are starting to show traces of certain hormones, antibiotics, fragments of recombinant DNA and RNA and other complex biological agents. They are coming from industrial processes, agricultural wastes and sewage treatment plants. I have seen data that suggests the same UV radiation will incapacitate some of these nasties as well.
The big question then is whether the SteriPEN Adventurer meets EPA standards and whether it has EPA registration. I asked the company about this, and they replied:
While our company is registered with the US EPA (company number – 73679), the EPA does not certify non-chemical water purifiers. As SteriPEN uses no chemicals it is not certified by the EPA. Non chemical systems such as ours and filters may be tested to the EPA standard. If these non-chemical systems meet the requirements of the EPA protocol then their literature generally states “meets US EPA protocol.”
According to the Lab Test Reports I have read the SteriPEN Adventurer (and the older Classic) do meet the EPA requirements for treating all three sorts of bugs, and the SteriPEN Adventurer is advertised as a ‘water purification device.’ Backpacking Light has no means of running the very complex biological tests required for this so we will rely on the work of the independent test labs. I am satisfied by these reports.
The SteriPEN Adventurer.
The pre-production prototype unit we received is shown here. The main difference between it and the production version seems to be the direction of the printing by the button. The black and yellow body holds two CR123 lithium (photo) batteries and the electronics needed to drive the UV lamp and control the operation. The little red arrow at the bottom of the picture points to a small pushbutton, which is the only control on the whole unit. The little green arrow to the right points to a LED which shines either red or green. The blue arrow points to a metal electrode: there is one of these on each side of the unit and they sense the presence of water. Somewhere inside the unit there is a lamp temperature sensor. The long glass tube is a strong quartz envelope enclosing the UV lamp itself. When traveling it is wise to put the cover over the lamp: it clips on very firmly.
To operate the unit you remove the cover from over the lamp, press the button once (for 1 litre) or twice (for 0.5 litre), and put the unit in the water to be treated. The metal electrodes must be below the surface of the water. The lamp comes on and stays on for the required time, then turns off. You are advised to stir the lamp around in the water a bit to make sure you irradiate all the water. The length of exposure depends on the number of button presses and the temperature of the unit; the microprocessor will calculate this for you. The variation in dosage time due to temperature is not large. There is some variation in efficiency of UV generation with temperature. The UV action on the bugs is not significantly affected by the water temperature.
The manual or booklet which came with the pre-production version had very brief operating instructions on page 3, while the rest of the booklet was devoted to marketing waffle. This is a pity – a smaller booklet with better instructions would have been appreciated. It may be that the production version will be better. Ultra-lightweight walkers may take some exception to the ridiculous claim on page 2 that ‘With the SteriPEN Adventurer, you’re carrying hundreds of gallons of pure water in your backpack …’ However, maybe I am being too harsh.
Blue Light coming from the lamp – or not, depending on the angle of view.
If exposure to the UV light can bump off the bugs, what will it do to you? This is the obvious question. This was addressed in a document entitled ‘Common Questions’ which I received, but I am not sure whether this document normally ships with the SteriPEN unit. As the document explains, UV light will not go through either glass or the common plastics; these materials block the UV. In addition, the company says the UV light bounces off the water/air interface at the top of the bottle.
In the pictures to the left the discharge can be seen in picture A, but it seems to be missing in picture B. In the case of picture B the lamp is still on, but the viewing angle from above is such that the blue light is being reflected off the water/air interface. In picture A you can see the blue light, but this is visible blue light, not the UV-C light. The UV has been blocked by the glass wall of the bottle. You can see visible blue light from the top of the water. The company claims that the UV light will not escape in this way but will rather be reflected off the water/air interface. They claim to have checked this with a UV light meter.
Another obvious concern is the effect on your eyes if you could turn the unit on before putting it in the water and got the UV in your eyes. Well, you can press the button, but the microprocessor has a mind of its own and for reasons of safety won’t turn the lamp on until it senses water at the metal electrodes. For this to happen the lamp has to be underwater. So far so good. If you take the lamp out of the water while the UV lamp is running the microprocessor will detect the loss of water and shut the lamp off in about one second. It will also turn the LED on with a red colour as a warning that the treatment time was not completed. However, it takes about a second or two for the loss of water to be sensed, and in this time the UV light may be shining in your eyes, so don’t pull the unit out of the water while it is turned on!
So why can’t you put the unit in the water first, before pressing the button? The reason is again safety. It would be safe enough if the lamp really was under water, but this may not be so. If the bottom of the unit is wet from the last immersion, the water sensor can be fooled into thinking that the unit is under water even when it is out of the water. The unit could be fooled into thinking it was safely under water and thus turn on in your hand as soon as you press the button – and blast your eyes. To prevent this the microprocessor has a rule that the water sensor must be ‘dry’ when you press the button for it to work. There is a trap here: if the bottom of the unit is still wet from the last immersion when you press the button, the unit may refuse to operate. You may have to brush the sensors dry with a bit of rag before you push the buttons. I was caught a couple of times like this.
This unit may have only one (input) button and one (output) LED, but it does have a microprocessor inside it, and using it sometimes seems almost as complex as programming a VCR. Well, not quite, but I found the following ‘features’ from testing and reading the User Guide.
- You have to turn the unit on before you put the lamp in the water.
That is, putting the lamp in the water first does not work!
- Pressing the button once turns the green LED on, first steady, then flashing fairly quickly.
The unit requires quite a definite press of the button to work: it is not hair trigger
- Pressing the button a second time makes the green LED flash quickly anyhow.
- The green LED goes off when the UV lamp goes on.
But if it flashes slowly while the lamp is on it means you are between 4,900 and 5,000 cycles: a warning.
- When the treatment is complete the LED will either flash slowly (for 1 L) or just stay on (for 0.5 L).
More importantly the UV lamp goes off, which is much more noticeable.
- If you take the unit out of the water before the time is up the UV lamp goes off within about 1 second and the LED glows red.
but putting the lamp back in the water does not turn the UV lamp back on.
- If you leave the unit turned on in the air, it will time out after about 15 seconds and turn off by itself.
It is supposed to give one red flash when it times out.
- Red flashing is obviously a warning, and has two meanings:
fast flashing: low batteries – flashes for 8 seconds.
slow flashing: lamp has done 5,000 operations and should be replaced.
- You can cancel the operation when the LED has turned red by pressing the button for a moment.
- You must dry the two sensors before you try to treat the second batch, or it may think the unit is in water still.
This can be a real trap if you are not thinking!
- Getting the lamp cover off is hard work: do it carefully so you do not break the lamp!
- There is no residual disinfection property like with chlorine and iodine.
More care may therefore be needed to keep the treated water clean.
However, I can’t tell beforehand whether it has been set to treat 1 litre or 0.5 litre.
Putting the SteriPEN in various water containers: it does not work with small-necked PET bottles.
Not listed above as a feature is the speed of operation, but that is because it is worth a separate comment. I have used most of the available filters over the years, and they take time to set up and then you have to sit there and pump for a while. That is, if you don’t have to stop and clean the filter half-way through. The pumping can be hard work. With the SteriPEN Adventurer I just sit there and stir gently for 90 seconds. Well, to be honest, my wife often does it while I do other things. With chemicals it does not take long to drop a pill in the water, or to mix Part A with Part B, but then you have to wait for 15 – 30 minutes (or more) before the water is safe. When you are thirsty, this can be a long time … I find I can wait the 90 seconds for the SteriPEN Adventurer fairly easily.
I did find that the SteriPEN Adventurer does not fit into every possible water container. In particular, it does not fit down the neck of my favourite ultra-light PET water bottles – which come free with every 1.25 litre bottle of fizzy mineral water. So using the SteriPEN has meant I have had to change how I treat our drinking water: now I do it in our cooking pot, with continuous stirring. I can pour the treated water into a bottle later. Mind you, since the lamp radiates out sideways rather than downwards the shape of the pot is just right for the light distribution from the lamp. I don’t think trying to treat water in a tall thin bottle is a good idea anyhow as the bottom region would not get much light. Alan Dixon has used a wide-mouthed hydration bladder for treating his water, as shown in the middle picture here, but the height of the bladder could be a problem. I don’t suggest you do it this way.
You should note that pouring water from one bottle into another after UV treatment is not without a risk: there is no residual purifying action once the lamp has been turned off. With Coghlans iodine tablets I know there is a trace of iodine still in the water which can handle later contamination. Since I currently use the same type of PET bottles for treated and untreated water, I have to be very careful to distinguish between the two (I put a spare rubber band around the neck of the treated water bottle)! Still, I can always use a little bit of the treated water to rinse out a ‘contaminated’ bottle; the chance of a harmful number of bugs being left in the bottle after doing that is very low.
Needless to say, my testing has been done on fairly clear water. After all, if the water is so turbid you can’t see through it then the UV light won’t get through it to the bugs either. It may make some sense to filter any mucky water through a bandanna or similar first – or to find better water if you can. But more importantly the presence of a small amount of dirt or organic matter in the water will not greatly affect the operation of UV light. This is very different from using a chemical, where organic matter in the water will soak up the chemical and may leave the bugs alive.
The User Guide recommends you do not use the SteriPEN when it is at a temperature below freezing. There are two good reasons for this. The first is that water below freezing may be … ice. Bit hard to stir the SteriPEN Adventurer in a block of ice! The second is that battery life for the 3 volt CR123A lithium cells does fall badly below freezing as shown in the graph below, and you need to look after those batteries. You may be aware that the Eveready e2 1.5 volt AA and AAA lithium cells have much better life in the cold than this, but that is because they have a different chemistry. The SteriPEN Adventurer is quite small, so it is no hassle to stick it in your pocket for a while to warm up.
I have found that people are sometimes more willing to use UV disinfection than chemicals because they want to avoid both the smell and taste of the chemicals, and to avoid their by-products. This is not a quantitative assessment, but for many walkers it is a real issue. One thing I can say is that the SteriPEN Adventurer does not seem to alter the taste of the water at all. This method of UV treatment may be the wave of the future.
With the SteriPEN Adventurer you are dependent on the life of the two CR123A lithium batteries, and those little batteries are not cheap. A good pair of these will cost in the region of US$12 – US$14, although cheaper ones may be available (with less life). You can also use the unit with rechargeable lithium cells, and the company sells a padded carry case with a built-in solar panel on the lid for recharging. The company claims that the cost of operation amounts to about 11 cents per gallon (4 liters) purified with rechargeable batteries, but I have no idea how much they are paying for their batteries, and prices and quality can vary widely. Testing was done with both the rechargeable CR123A cells and the readily available standard CR123A non-rechargeable lithium cells.
Life of a CR123 under pulsed load (courtesy Duracell).
The current drain from the batteries starts out at about 1 Amp: this is a lot for the little CR123 cells. Fortunately they were designed for photographic use and can take that sort of load in short bursts. After about a minute, when the lamp has warmed up, the current drain drops to about 0.9 Amps. This represents a load of about 2.7 Watts (per cell), and typical battery life at that sort of continuous load is about 0.85 hours to 2.0 volts and 1.0 hours to 1.55 volts. I do not know the minimum voltage which the SteriPEN Adventurer will operate at as this is a little hard to test. However, this does not matter very much since when these cells reach their end of life the cell voltage falls quite fast.
With a pulsed load the life of the CR123A cell is longer, and we can treat the SteriPEN as a pulsed load, albeit a fairly harsh one. Using a graph from Duracell, we can see (thin blue cross hairs on the red line) that at 0.9 Amps and a low duty cycle the life of a cell can be as long as about 1,800 x 3 seconds to 2.0 volts, at ‘room temperature’ (RT). This is 90 minutes. The SteriPEN Adventurer takes about 90 seconds to treat 1 litre of water. This suggests that one set of CR123A Lithium cells will treat 60 litres of water, at ‘room temperature.’ At US$13 for two cells, that is about 22 cents per litre. I can’t tell you how many days walking this translates to as everyone’s water use is different. Remember that if you are going to boil some of your water for cooking, you do not need to treat that part with UV first.
The graph also illustrates the very bad effect sub-zero temperatures have on battery life! You can happily use the SteriPEN Adventurer in the snow if you warm it and especially the batteries up to body temperature first.
SteriPEN Adventurer battery compartment.
Replacing the batteries in the field is very simple with the SteriPEN Adventurer. The end cap is held in place by a screw, but this has a huge head with a huge slot (red arrow) which I can operate with my thumbnail or almost anything. It does not seem to jam at all. Undo the screw and the cap comes off. The batteries just slide out. Insert new ones with the small terminal pointed upwards as shown in the picture and replace the cap – there is a small retaining lug at the right hand side of the picture below the green arrow to hook in place. If you forget and put the batteries in upside down it does not matter as nothing will happen. There is a shaped contact at the tip of the green arrow which will only mate with the small battery terminal; it won’t connect with the large terminal at the other end of the battery. I won’t say it is foolproof, but it comes close. Check that the new batteries work by pressing the button. The green LED should come on. You can either now use the unit to purify water or just leave it alone. After a little while (about 15 seconds) the microprocessor will get tired of waiting, flash the red LED once and then cancel the operation.
If you are going to store the unit in the drawer for a long while between trips you are advised to take the batteries out during storage. I found the unit does draw a few milliamps when turned ‘off.’ This is because the microprocessor is running all the time, obediently waiting for your next command. This takes power. It is easy to take the batteries in and out between trips. The metal screw on the cap engages with a metal nut on the body (rather than plastic), giving the fastener a long life.
SteriPEN Solar Charger, open and shut, showing solar panel.
The SteriPEN Adventurer will also take two rechargeable 3 volt CR123A batteries, but recharging these requires a special recharger. I have not seen any suitable generic rechargers on the market, but SteriPEN sells a solar-powered recharger for these called the SteriPEN Solar Charger. The charger’s case will also protect the SteriPEN Adventurer and comes with a foam cover (not shown) that can be tied onto the top of your pack. The company says the Solar Charger can recharge a pair of the CR123A cells in about 2 days if the sun is good, but if you recharge the batteries every day it certainly won’t take that long to top them up. For instance, if you have treated a few litres of water in the evening it should charge up with an hour or two of reasonable sunshine the next morning. I am not sure how one tells when the batteries are fully charged this way, but I gather the Solar Charger won’t hurt the batteries.
This is an interesting concept, but the empty Solar Charger weighs 160 grams (5.64 oz) while a pair of spare batteries weighs only 30 grams (1.06 oz). Each pair of rechargeable batteries will treat about 50 litres (100 pt) of water. The extra weight of the Solar Charger seems an unnecessary burden while walking – in general you would be better off taking spare batteries. I have yet to consider giving the Solar Charger the ‘UL treatment’ to reduce its weight for very long thru-hikes – that would of course completely void the warranty.
The Solar Charger can also be driven by a universal plug pack from the mains, and this option is far more useful in my opinion. The plug pack can take anywhere from 90 volts to 240 volts, which means it can be used around the world. (Australia, where I live, uses 240 volts). The plug pack has pins for an American wall socket, but adapters can be bought. The plug pack connects at the hole in the side of the Solar Charger shown with the red arrow. There is a red LED beside that hole: this glows brightly while charging, and dimly (if at all) when the batteries are fully charged. I guess it measures the current flow. This option seems to me to be the one I will use most of the time.
Frankly, I think that disinfection by UV has enormous potential for outdoors use. The current ‘wand’ may be a little heavier than we would like, and certainly the drain on the batteries is fairly severe. Within a few years I would hope to see suitable UV LEDS being available, and I am sure the company will be very eager to release an LED-based wand with ten times the battery life, running off two lithium AA cells. When this happens I want to see the UV light shining downwards into the depths of the bottle rather than out sideways as it does now. I can dream – in the meantime this unit works fairly well.
Ideally, when the new unit is introduced a new lighter solar panel might accompany it. This should be a flat unit consisting of just the solar cells, with a power lead coming out and a small socket on the new wand. That way you could recharge the cells in the wand while you walk.
- No chemicals – no taste (feature shared with Aquastar unit)
- No long waits (feature shared with Aquastar unit)
- Lightest UV treatment unit on the market
- Comes with field recharger
Recommendations for Improvement
- Move to UV LEDs
- Have the UV light shine downwards into the bottle as well as sideways
- Reduce current drain
- Switch to two lithium 1.5 volt AA or AAA cells
- Lighter Solar Charger panel, scrap the case
- eg Chlorine dioxide at 5 C (41 F) against Giardia and Crypto.
- Vendors of different chemicals may try to dispute this, but that’s what comes out of independent academic research.