An engineer will have to answer the fine details of ash ejection. I know that one system was used in port and another at sea. Also, I know that most of the "dirty work" of disposal was done at night when it would be less obvious to passengers who might take offense. I recall steamboats on the Great Lakes would also "blow their tubes" at night. This was a process that cleaned out the exhaust gas uptakes from the boilers and sent lots of black crud into the air.
Ash ejected beneath the ship was wetted down enough in the process that it sank quickly and..at least from the surface..disappeared. I am sure there must be a trail of ejected ash from steamships lying on the bottom beneath all of the major steamer routes. So far, however, I've not seen a report that this ash and clinkers have harmed anything. Perhaps no one has studied the question.
Ships in 1912 may have developed a lot of garbage..that is waste food..but little pollution. Dumping waste human food into the ocean provided more biomass for the critters of the deep. If nothing else, the gulls loved it. The other stuff in 1912 dumping was not really harmful. Steel cans in the trash would quickly deteriorate and glass bottles are pretty much biologically intert.
The problem with modern dumping is plastic. The damned stuff never goes away. Worse, much of it is a deathtrap for living critters. Of particular concern are those sets of plastic rings that hold soft drink and beer cans together. And, in 1912 the garbage and trash was put into steel barrels ("trash cans" in the U.S. and probably something akin to "dust bins" in the Mother Country) that were dumped, washed and re-used. Today, we wrap our garbage in...guess what...plastic! What Titanic left behind from its galleys may not have been pretty, but it was more helpful than harmful to the critters of the sea. This is not true of todays trash.
-- David G. Brown
