On 24/01/2019 18:13, Chris J Dixon wrote:

I was involved in planning work on a trial system to be fitted in
place of an inboard retention tank (which was abandoned once the
real cost/benefit figures began to emerge). This was very similar
to the kit used on submarines, and was essentially a
bio-digester, which produced clean water of a quality suitable
for flushing, thereby much extending the service intervals.

I think India and Russia use something like that on some /very/ long
distance trains.


--
Arthur Figgis Surrey, UK