Thames water purification on the run: a solution
By Julien on Wednesday, July 7 2010, 18:10 - ThamesSourceQuest - Permalink
After a brief survey of what nasties are waiting for me in the Thames, I tried to find a suitable water purification system. And it's not easy. Ideally, it would be a all-in-one integrated system based on a hydration bladder with two pipes: one regular pipe for drinking and another connected to a pump+microfilter that could be stored in the backpack side nets. No need for extra chemical and no need to remove the bag to either drink or re-fill. I actually know of one such system, the Lifesaver Hydrocarry, which is only available to the military. Otherwise, you would have to build it yourself (*).
Back to reality now. I've considered the following purification systems:
There are a lot of contradictory opinions on all filters. I need to make a few trade-offs on weight, what is filtered, and the flow. I've decided to make no compromise on water quality and therefore filter everything, which is debatable, since the viral risk is relatively low in the Thames. This means I need a 0.2 to 0.3 micron filter for protozoa and bacteria (every system has got that), activated carbon filter for chemicals and taste, and some form of virus elimination. I didn't want to put extra chemical after filtration, which makes the whole process a bit fiddly.
Besides, all the systems with a nominal flow under 1.5L/min put me off a bit. Indeed, this is the highest achievable flow and could be much worse depending on turbidity. Users have reported flows down to 0.2L/min with some systems, ie. 5 minutes to fill in 1 litre. This is not suitable on the run.
So I was essentially left with the all-in-one bottle systems. With such systems the flow is less of an issue, as the filtration happens whilst drinking, ie. during the run and not during the filling-in breaks.
I had decided to get sponsored for the purification system. This decision was not only driven by the financial aspect, it's also to make sure that the system is actually going to work. Manufacturers want good publicity, not the story of a runner who either had to stop due to a filter malfunction or even got poisoned using their product. So I assumed they would accept only if they trust their system to filter the Thames water appropriately. I've contacted the three short-listed manufacturers. Two of them didn't bother to reply and the third promptly accepted to sponsor my challenge, but then didn't follow up for some reason.
Therefore I've decided to buy the Katadyn Mybottle Purifier and the PureHydration Aquapure Traveller, the LifeSaver being much heavier and bulkier. My original idea was to carry both, as if one system fails during the run for whatever reason, I won't be stuck with no water. Given the weight and volume they take, I might actually take only one in the end. In order to choose, I've tested both of them using some fresh Round Pond water from central London. I have to say it looks rather green at the moment and the dense population of ducks/swans/geese doesn't help with the water colour.
The Round Pond during the water sampling
I've put side-by-side the untreated water and the two others. The untreated water had a green-yellowish taint, but didn't actually smell. Both purified waters looked clear. The main difference between the two systems is how they eliminate viruses. The MyBottle relies on eletrokinetic filtering, whereas the Traveller is iodine-based. This technical difference leads to a number of very practical implications:
Obviously, the weight and flow are in favour of the Traveller, but I'm not sure I can see myself waiting and timing 15 minutes. Or maybe I can turn this downside into a feature by setting a routine: fill in, wait 15 minutes, drink half-a-liter during the next 15 minutes, repeat? As for the iodine taste, it can be removed using vitamin C, but I'm not sure how to do that in practice, as that would probably mean transfering the filtered water into another container.
Ultra water.
(*) This could be done rather cheaply using for example the Aquapure inline filter and a bladder, but you would face some watertightness issues when incorporating the second pipe in the bladder.
Back to reality now. I've considered the following purification systems:
| System | Main | Viruses | Carbon | Flow | Weight |
| microns | L/min | g | |||
| All-in-one | |||||
| Katadyn MyBottle + ViruPur | 0.3 | yes | yes | 0.2 | 260 |
| PureHydration Aquapure Traveller | 0.2 | yes | yes | ? | 128 |
| PureHydration PureLink (inline) | 0.2 | yes | yes | ? | 120 |
| LifeSaver Bottle | 0.02 | yes | yes | 2.5 | 635 |
| Ceramic only | |||||
| MSR Hyperflow microfilter | 0.2 | no | no | 3 | 209 |
| Katadyn Mini | 0.2 | no | no | 0.5 | 210 |
| Ceramic + carbon | |||||
| MSR Sweetwater microfilter | 0.2 | no | yes | 1.25 | 320 |
| Katadyn Hiker | 0.3 | no | yes | 1 | 310 |
| MSR Sweetwater purifier | 0.2 | yes (chem.) | yes | 1.25 | 397 |
| Katadyn Vario EU | 0.3 | no | yes | 1 | 460 |
There are a lot of contradictory opinions on all filters. I need to make a few trade-offs on weight, what is filtered, and the flow. I've decided to make no compromise on water quality and therefore filter everything, which is debatable, since the viral risk is relatively low in the Thames. This means I need a 0.2 to 0.3 micron filter for protozoa and bacteria (every system has got that), activated carbon filter for chemicals and taste, and some form of virus elimination. I didn't want to put extra chemical after filtration, which makes the whole process a bit fiddly.
Besides, all the systems with a nominal flow under 1.5L/min put me off a bit. Indeed, this is the highest achievable flow and could be much worse depending on turbidity. Users have reported flows down to 0.2L/min with some systems, ie. 5 minutes to fill in 1 litre. This is not suitable on the run.
So I was essentially left with the all-in-one bottle systems. With such systems the flow is less of an issue, as the filtration happens whilst drinking, ie. during the run and not during the filling-in breaks.
I had decided to get sponsored for the purification system. This decision was not only driven by the financial aspect, it's also to make sure that the system is actually going to work. Manufacturers want good publicity, not the story of a runner who either had to stop due to a filter malfunction or even got poisoned using their product. So I assumed they would accept only if they trust their system to filter the Thames water appropriately. I've contacted the three short-listed manufacturers. Two of them didn't bother to reply and the third promptly accepted to sponsor my challenge, but then didn't follow up for some reason.
Therefore I've decided to buy the Katadyn Mybottle Purifier and the PureHydration Aquapure Traveller, the LifeSaver being much heavier and bulkier. My original idea was to carry both, as if one system fails during the run for whatever reason, I won't be stuck with no water. Given the weight and volume they take, I might actually take only one in the end. In order to choose, I've tested both of them using some fresh Round Pond water from central London. I have to say it looks rather green at the moment and the dense population of ducks/swans/geese doesn't help with the water colour.
The Round Pond during the water sampling
I've put side-by-side the untreated water and the two others. The untreated water had a green-yellowish taint, but didn't actually smell. Both purified waters looked clear. The main difference between the two systems is how they eliminate viruses. The MyBottle relies on eletrokinetic filtering, whereas the Traveller is iodine-based. This technical difference leads to a number of very practical implications:
| MyBottle | Traveller | |
| Weight | 260g | 128g |
| Flow | very slow | slow but easier |
| Taste | clear | iodine |
| Delay | instantaneous | 15 min iodine dwell time |
Obviously, the weight and flow are in favour of the Traveller, but I'm not sure I can see myself waiting and timing 15 minutes. Or maybe I can turn this downside into a feature by setting a routine: fill in, wait 15 minutes, drink half-a-liter during the next 15 minutes, repeat? As for the iodine taste, it can be removed using vitamin C, but I'm not sure how to do that in practice, as that would probably mean transfering the filtered water into another container.
Ultra water.
(*) This could be done rather cheaply using for example the Aquapure inline filter and a bladder, but you would face some watertightness issues when incorporating the second pipe in the bladder.