The first toilets in airplanes were simple buckets. Today and happily for people leaving close to airports, or under flight paths, there is no more falling manure. Special designed Lavatory Service Carts collect the wastes for final disposal into the airport sewage facility. The mains constrain in aircraft lavatory concept is weight.
Toilets flushing system, even with recycled water, represent an important weight to fly around.
Toilet designs offer to passengers and airlines a compromise between comfort and operating cost. The classical lavatory This type is mainly seen in aircraft manufactured before the mid 80's and offers passengers a reasonable comfort and flush plentifully. Applying a layer of toilet paper on the stainless steel bowl, before use, guaranty a good wash with a single flush. The conventional, non confusing, flush handle is used correctly by all passengers. One known incidents is wallet drop of when pulling up pants, the pick-up is easy but requires a generous wash.