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Rick Morel

On Mon, 20 Apr 2009 08:22:29 -0700, wrote:

snip

Now trapped in a high pressure environment, at some point, the bacteria
explodes, releasing its internal load of really small toxins onto the
surface of the membrane where it can, because of its tiny size crude
molecules pass through the membrane with the H2O, contaminating the
outlet water. The key, I'm told, is the high pressure, which rips many
biologicals apart into tiny pieces. I don't see why this is not a
possible scenario and a source of possible sickness for the drinkers.

Doesn't happen. The bacteria normally is not "trapped". The little
bugger is spun around and bounced around, then spit out of the reject
line.

That's *one* possibility of course, but with millions of opportunities,
over time, many of the little buggers do get "caught".

Okay, I guess I took too far a stance in the opposite direction.
Agreed that many will get "caught" - it's as incorrect to say none
will as it is to say all will. However, the point of the flow rate is
to wash these away.

BTW, the poor little creature would implode, not explode.

Well, considering its fluid filled, how would it implode? It will be
lysed in either event.

Definition of lysed: The disintegration of a cell resulting from
destruction of its membrane by a chemical substance, especially an
antibody or enzyme

I honestly don't see how this would apply, unless it's a normal event
of decomposition? Is that it? I plead ignorance and welcome any info.

Implode/explode. Okay, I'll go with both are impossible because it's
fluid filled. This then negates any effect of high (or low) ambient
pressure in either event, so that argument is thrown out.

snip

Again, all this is flushed out after a few minutes. It's simply a
matter of rejecting the first few minutes of product water.

Dumping the first few minutes of product is always a good idea.

Actually I would say it's a necessary idea. Wait, that reads
sarcastic. I don't mean it that way. I simply mean that I think it's
a necessary part of using an RO system.

Rather than play theory, here's the results of my real world
experience cruising and supplying water from RO:

Last go round I made on average 5 gallons of water per day for 2
years. That's a total of 3,650 gallons of drinking water with 36,500
gallons of reject water passing across the membrane and going
overboard. Very little of that total 40,150 gallons of water was
"clean sea water"; most of it came from bays, a bit from rivers. Some
very silty.

The setup included 2 prefilters - a 20 micron followed by a 5 micron.
The filters were inspected and cleaned frequently, and replaced as
necessary.

The routine, as above, was to reject the first few minutes, test, then
route to the tanks. The first good half gallon or so went into a
container, then this water was run through the system at shutdown.

A biocide treatment was done when the watermaker wasn't going to be
used within a couple days (The total time period was more than 2
years).

The membrane never got an acid and/or alkyline treatment. The reason
is product water flow was basically the same at the end as at the
beginning. I didn't have a flow meter then (I do now on the new boat),
but every two weeks I measured how long it took to fill the shutdown
container to a half gallon mark. It normally varied by a few minutes,
depending on temperture, etc. That one was a 1.5 GPH unit. I now have
a 3.4 GPH.

Now maybe I was lucky, or maybe it was the care and attention I took.
The manufacturer did not recommend the cleaning treatments unless
necessary.

A couple points. I now have a TDS meter, but the best "tester" is a
human. Smell, then taste.

Don't get a too big watermaker. Size it to run at least a couple hours
a day, and run it every day to top off the tank. Membrane fouling and
all that bad stuff happen when they're idle.

It bears repeating. If you don't run it every day, or at least every
two or three days, you will have problems. Do the biocide treatment
(pickle it!) if you're not going to run it for more than a few days.

Thousands (tens of thousands? hundreds of thousands?) of people drink
RO water every day. On boats, ships, islands, Israel, and now
California from processed sewerage water. I guess some get sick from
it. It would be interesting to see what percentage compared to those
that get sick from city water and bottled water.

Rick Morel