Rick Morel wrote:

This high pressure traps the bacteria against the membrane, where I
suppose it's like his little head is stuck in a hole his body can't fit
through, a crude cartoon-of-the-mind's-eye.

Never heard of that.

Happens all the time. Biofilms are the bane of RO systems and need to
be addressed through proper membrane care (cleaning, sanitizing,
replacing, etc.). RO membranes provide a perfect substrate for bugs,
and the constant flow provides a fresh source of nutrients. Take care
of the system, however, and it need not be a problem.

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".

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.

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.

Keith Hughes