Toilets on commercial airliners function differently from those found in residential or commercial buildings. They operate based on two primary methods: the vacuum system and the recirculating system. Here's an explanation of both systems:

1. Vacuum System (Most Common):

- Waste Collection: In the vacuum system, a powerful suction is created using a Venturi tube or an electric vacuum pump. When the toilet is flushed, a valve opens, and the suction pulls the waste and water from the toilet bowl into a holding tank.

- Holding Tank: The waste and water mixture is deposited into a holding tank located in the belly of the aircraft. This tank can hold a significant amount of waste and is fitted with sensors to monitor its capacity.

- Deodorization: Chemicals or disinfectants may be added to the holding tank to mitigate odors and disinfect the waste.

- Tank Disposal: Upon landing, a ground crew retrieves the waste from the holding tank using the aircraft's external waste port. The collected waste is then properly disposed of according to environmental regulations.

2. Recirculating System (Less Common):

- Waste Treatment: The recirculating system incorporates both mechanical and chemical processes to treat and sanitize the waste.

- Macerator: As the waste enters, it passes through a macerator that grinds it into smaller particles.

- Chemicals: Disinfectant chemicals are applied to treat and sanitize the waste.

- Filtration: Multiple filtration stages ensure the removed pathogens, solids, and debris.

- Recycled Water: Treated water can be reused multiple times for flushing, while solid waste remains collected in a compartment or tank. After the aircraft lands, the tank needs to be serviced much like with vacuum systems.