http://www.ananova.com/news/story/sm_790942.html

The article above seems to imply that airliners just eject the waste
out of the side, where it falls to earth as frozen chunks.  Surely
not?

So tell me, what really happens?

Hello spurious-ga,
 
Thank you for your question.


Airlines are not permitted to dump toilet waste. The waste is kept in
tanks until landing and then the ground crew pumps out the tanks and
hauls the waste to a treatment facility.

From the Chicago O'Hare Flight Standards District Office:

“Many people are of the assumption that aircraft lavatories dump
overboard when they are flushed, this is not the case.   Lavatory
waste is contained on the aircraft in a holding tank until the
aircraft lands.  When the aircraft is safely on the ground, only
ground crew personnel may operate the valve to dump the waste tank. 
While in flight it is physically impossible for the pilots to dump the
waste water because the valve is usually located on the exterior of
the aircraft.”
http://www2.faa.gov/fsdo/ord/blueice.htm


“The first toilets in airplanes were simple buckets. Information on
early flushing systems is not available, however aircraft's cabin were
not pressurized and it was easy to open doors and windows...

Today and happily for people leaving close to airports, or under
flight paths, there is no more falling manure. However planes still
have to be purged of their smelly "unpaid load". Special designed
Lavatory Service Carts collect the wastes for final disposal into the
airport sewage facility.”
http://www.asiaspirit.com/lavatory.html


Aircraft Ground Support Equipment - Lavatory Service Carts
http://www.gsesales.com/lavatory_carts.htm
 

“Construction sites, airplanes, many boats and recreational vehicles,
and some rural parks will have port-a-johns where you can flush the
waste into a holding tank. The fluid is not the water used in standard
household toilets. It blocks or masks the odor, and slows
decomposition, until some lucky soul gets to pump out the tanks and
haul the waste to a treatment facility.”
http://www.virginiaplaces.org/waste/sewer.html


Regarding the article you mentioned, perhaps there was a leak in the
waste storage tanks of the aircraft.

“Airlines are not permitted to dump lavatory waste while in flight.
FAA spokeswoman Holly Baker said that if blue ice hit the Cadamores'
house, a leak most likely occurred in a jet lavatory. At higher
attitudes the leak forms ice on the aircraft. As the jet descends, the
ice warms and starts to fall off the plane.”
Gazette.com Local News
http://www.post-gazette.com/neigh_north/20021121blueicenp3.asp


Search Criteria:

lavatory waste system
aircraft waste
airplane toilets
waste storage tanks +aircraft



I hope this helps. If anything is unclear please request clarification
and I'll be glad to offer further assistance before you rate my answer
and close the question.


Best Regards,
Bobbie7-ga

Thanks for the prompt answer, bobbie7-ga.  Sunbathing in my garden
watching the contrails in the summer sky and feeling the gentle caress
of a light drizzle on my face, I have often contemplated the
intricacies of airline toilet plumbing.

Spurious,

Thank you for the five star rating.

Here is some additional information that may interest you:

AIRCRAFT TOILET SYSTEMS 

“Conventional aircraft toilets recirculate the holding tank solution
through flush rings around the stainless steel bowl by means of an
electrical circulating pump. The newer type aircraft now have a vacuum
operated system, which sucks the waste along with about half a pint of
potable water for flushing purposes into a common holding tank. As the
customer never sees the holding tank solution, chemical deodorants do
not have as important a role as they do in the more common
recirculating types.


Aircraft toilets are constructed primarily of stainless steel with the
exception of the holding tanks, which are usually of a composite
material. “

SERVICING AIRCRAFT TOILET TANKS

“The toilet holding tank may be a part of the individual toilet
assembly or, as in larger aircraft, it may be separate, servicing
several toilets. When serviced, the tanks are partially filled with a
deodorant solution (water solution of a concentrated product), which
is emptied and recharged at the next scheduled service stop. This is
normally done with ground service trucks equipped with two tanks, one
for picking up the waste material and one for flushing and recharging
the holding tanks with fresh solution. The waste is released to the
sanitary sewer and the deodorant tanks are recharged with fresh
solution, usually at the same site in preparation for another service
run. For liquid deodorants the service trucks can be charged with the
proper concentration of deodorant, either by hand measurement or by
metering into the fill water line with a proportioning device, which
can be done with a siphoning device or an electrical metering pump.
Some service trucks carry the concentrated deodorant and meter it
directly into the aircraft in soluble packs or aluminum foil.”
Source: Chemetall Oakite News 
http://www.oakite.com/newspub/story.cfm?ID=96


From how stuff works:
How does the toilet in a commercial airliner work?
http://www.howstuffworks.com/question314.htm

Better not to ask where trains dump their waste ...

However, I seem to recall reading that for some years airliners
allowed the fluids from their lavatory SINK drains to vent to the
outside. It was thought that this small amount of water and soap would
evaporate and therefore just "disappear." Then epidemiologists began
to wonder why some diseases seemed to be spreading along unusual
patterns. It was realized that these patterns were spokes that lay
under the flight paths of airliners flying away from cities in which
the diseases were well-established. The bacteria or viruses being
washed off the hands of the infected were surviving their slow drift
down to earth from the airliners. But that's just what I recall
reading; maybe I'm imagining it.