I have to say that when I first heard about this – a portable, UV light water purifier running on batteries – I was sceptical, but that scepticism blossomed when I first used it. Basically, you to pop in 4 AA batteries into this rocket shaped device, press a button and wiggle it around in water during which time a UV lamp comes on and fries the nasties. After a minute and a half later you have, apparently, safe drinking water. I did all this thinking: yeah, right.
I mean, the great thing about traditional water filters is that you get to do something concrete – you pump, water gets strained of impurities, you feel safe. The disconcerting thing about the SteriPen is that you don't really get to feel that anything's happening. A blue light comes on which the instruction manual confesses is just there for show ( i.e. to show you that it's on and working – the UV light is beyond the visible spectrum) but beyond that, you have to rely on the manufacturer's word and a raft of US federal Environment Protection Agency tests. Granted, that's pretty good, but it's not as good as a rigorous outing in one of the fiercest testing grounds a water purifier can have: India – land of the hygienically challenged.
The subcontinent is a place where 'rural toilet' means 'down by the river', where newspapers periodically run exposes on the pollutants they've found in bottled water and where antibiotics rapidly become your closest friends. It's a fertile breeding ground for everything that makes you ill, but it's here that I've been using the SteriPen for two months and passed barely a loose stool yet. In short, it appears to work extremely well.
Once you fathom the basics, the SteriPen is simple to use. You press a button once for a litre, twice for half a litre, then stir the lamp for up to 90 seconds in the water. The germicidal UV light destroys the DNA of viruses, bacteria and protozoa, preventing them from reproducing and leaving the water safe. This is in fact the method used by many municipal water plants, hospitals and bottled water companies: the SteriPen is just a portable version of a well tested technology. It's quick, effortless, produces instant clean water (a major plus over many purification systems) and – as far as it goes – is magic.
I say as far as it goes because it does have its limitations, the biggest of which is power. It eats batteries, especially in the cold. Manufacturer's tests claim to get around 10-15 litres from four standard alkaline AA batteries which means it's expensive to run, but if you use NiMH rechargeables then you get around 75 litres per charge. Although this is fine if travelling in areas where you have reasonable access to electricity, for extended trips into the mountains you'd have to think seriously about your power supply. Would a few boxes of alkaline batteries be practical in an expedition situation, for example, or indeed acceptable from an environmental point of view?
The second biggest issue for the SteriPen is that it can't sterilise dirty or sedimented water, so if you don't have access to a clear supply then you'd need a filter. A bulky, rudimentary 'pre-filter' does comes with the supplied Nalgene bottle, but having tested this in the glacial silt laden Ganges, I can tell you that it doesn't get the water sufficiently clear for the SteriPen to work. The manufacturer recommends leaving the finest silt to settle before decanting the clear water; but, realistically, when was the last time you waited an hour or more for a sip? or tried settling sediment in the back of a jiggling rucksack? That said, it's rare not to have access to a clear water supply from a side stream or puddle in the hills, and it's certainly not an issue I've been constrained by yet.
One final niggle is that although the SteriPen comes with a decent protective cover, the lamp is made of quartz and could very easily be broken (I've almost managed it a couple of times already). You can get the lamp replaced – and it needs it after 5,000 litres of use – but this isn't much good if you're relying on it in the way you tend to with water purifiers. You do need to be a little careful.
In spite of these limitations, though, in the past few months I've been hugely impressed – not something I'm used to when it comes to gadgets for cleaning up water. I've been running it on rechargeable batteries with great success and would highly, highly recommend it for travel, but would have reservations about using it for more heavy duty, expedition situations. But as future models get smaller and more efficient, one day I suspect the SteriPen could be the way to purify water in the hills.
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