A macerator is a unique part of a waste disposal system designed to encourage the smooth and compact flow of waste through the system. This is usually accomplished using a two-part system of steeping and cutting. First the waste--usually toilet waste--is thoroughly soaked in some kind of liquid, often water. This steeping softens the waste, saturating it and making it easier to manipulate. The second part of the macerator system is a rotating blade mechanism that cuts at very high speeds in a fashion similar to a blender, dissolving the waste into very small particles that make it much easier to pump and transport.
The system works via a series of valves and automatic measurement systems. Flushed waste is pumped or allowed to drain in the main macerator chamber. Here it is combined with water or another liquid, which is pumped in through a separate pipe until the waste accumulation reaches a certain level. This particular level of waste is usually detected via a pneumatic switch or some other type of sensor that measures the pressure inside the tank and starts the macerator when the pressure is high enough.
The valves that allow both the waste and the water through are temporarily closed via flaps or other locking mechanisms, and the blades of the macerator start running. These blades can turn very fast, up to 3,000 or 4,000 revolutions per minute, fast enough to turn all the saturated waste within the container into small particles. A separate pumping mechanism then draws this liquefied waste out of the chamber and onward. This lessens the pressure, and causes the switch to turn back off, stopping the blades and opening the pipes for the cycle to start again. Many macerators perform this cycle every time a toilet is flushed, although there are variations.
Where the liquefied waste goes depends on where the macerator system is built. A land-based macerator pumps the liquefied waste in soil stacks or septic tanks where it can decompose more easily than normal waste. However, most macerator systems are used on board ships or boats, where land is far from reach and the waste needs to be disposed of in some other method. On sea vessels, the macerator liquefies waste so that it can be pumped safely overboard or into on board septic tanks with maximum use of space.
There are other options for disposing of waste on board very large ships. These vessels usually have enough power to run much more complicated systems that use electrical currents or chemical reactions to dissolve or decontaminate waste. A macerator is preferred by operators of smaller vessels because of its relative affordability and simple installation requirements.