As usual your reply is informative and kind.

My personal opinion is that is uncorrect to dump anything in coastal
waters,
also soapy water...

That would be a valid concern in many parts of the world where
....CUT...
. So the only
pollutants in soapy water are from whatever the soap was used to
clean...for instance, an oily bilge.

You aven't got my point: disregarding the legal point or even the chemical
pollution, the soap can be safe and not chemically polluttant (maybe...)
But you can guarantee that the oil (only to remain with your example...)
that the soap as removed is also safe and not polluttant?
And even if it is safe, do you tink that a place full of soap bubbles and
oil and watermelon seeds floating around is nice place where to send the
boys to swim?

......

I have read the lectra/sans manual.
I am not a specialist, like you, but, if memory helps, salty water
electrolisys produces clorine... (I am right?)

So far...but--

this means that the s**t is
macerated and disinfected... But it remains s**t, nice dark s**t.

No...that's a common misconception among "no discharge" proponents.
First, it assumes that every flush is fecal matter...when in fact,
unless someone onboard has a serious gastrointestinal problem,

ROTFL...

only one
or at most two flushes person do...the remaining average 4 toilet
visits/day/person are urine only.

I do believe that your urine don't stinks... mine definitively do...
OK, only kidding.

Second, the average person
output--including solids--is only about 8 oz...the average flush
including flush water is about half a gallon. So the treated discharge
is highly diluted to begin with. Third, the hypochlorous acid
(chlorine) created by the Lectra/San not only reduces bacteria count to
less than 10/100 mililiter, it also bleaches as it treats...so what
comes out is only about a half gallon that closely resembles skim milk
that's been cut about 2:1

Another lesson learned: while swimming, stay away from that looks like
milk...

with water....so "thin" and pale in color
that, unless the thru-hull is very close to the waterline, it's totally

Maybe that the perfect arrangement is your lectra/san discarging into a
tank, to be dumped at marina or 3 NM away from coast. This would solve also
the odor problems... or not?

I would like a similar solution, but, it as obvious, it has down aspects:
1) it needs power. Power, in small sailboat, is a constant concern. You
aren't guaranteed to have it.
2) it needs maintenance. I don't bet on accuracy of maintenance, when, safe
or not, all is dumped overboard...

I have checked also the prices of lectra/san... and it is expensive...

I am building a cat and I was planning to install a Lavac head (manual, no
power requirements...) with tank.
But msd+tank appears interesting...
It is expensive and needs space, but in case of failure of msd the tank can
save the day.

Paolo