Watermaker Membrane Question

[F51]

It seems to me that if amoebas and bactiera are larger than salt water molecules, the watermaker might be a good way to get potable water from contaminated water. But I don't know if the little beasties can go thru the membrane or not. Anyone have the facts? Thanks.

[Captain Bill]

Originally Posted by F51

It seems to me that if amoebas and bactiera are larger than salt water molecules, the watermaker might be a good way to get potable water from contaminated water. But I don't know if the little beasties can go thru the membrane or not. Anyone have the facts? Thanks.

They cannot pass through an intact membrane. This does not preclude them from getting through small pinholes or past leaky seals. This is why virtually all makers say not to use them in contaminated water. You would of course see increased TDS readings if you were having these problems in salt water. In fresh water you might not be able to tell.

[Tellie]

There's a bit more to watermakers than just a membrane a pump and a handful of plumbing parts. In a "Perfect" world yes, running a salt water membrane in contaminated water will produce safe drinking water, depending on the contaminates. The problem usually is not so much with the watermaker itself, which can have issues, but rather the pre-filtration. Most boat based watermakers have a fairly simple pre-filtration system usually a 20 to a 5 Micron rating. Anything smaller than 5 Microns should easily pass through the system and overboard through the brine discharge. I always say that boat based watermakers are off shore pieces of equipment because of their simple pre-filtration. The problem with areas where water is known to be contaminated is that this can easily and quickly clog a simple pre-filtration system. Now you get into adding things such as media filtration and the such to pre-treat the water first. These can be found on boats in areas such as the PNW but for the most part are limited to larger yachts where we install very large watermakers and also the land based systems I sell and install. These are systems that we know in advance, by water testing, will have a certain amount of contaminants and we design a proper pre-filtration system to meet these particular needs. These systems vary from application to application and work great, but they can cost more than a simple boat based watermaker itself. You can't always avoid contaminants 100% of the time, but you can make sure you run your system in the cleanest waters you can find. I also sell portable type survival watermakers that are designed to either run from your boat or in less than desirable waters. These will run off their own solar power as well. These would be more practical in contaminated waters.


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