A macerator is essentially a blender blade
A macerator is not a pump, but a "chopper" blade IN a pump. They're installed in electric macerating toilets and in pumps designed to dump a holding tank at sea. The macerator pumps designed to dump a tank are usually referred to as just a macerator. The actual pump, whether in a toilet or in an overboard discharge pump, is typically an impeller driven pump. An impeller gets its name because it impels liquids through the pump.You can see an exploded drawing of the most common macerator pump here: http://www.jabsco.com/files/18590_series_sealed_macerator.pdfThere are two other types of pumps--manual diaphragm pumps and electric diaphragm pumps. They don't macerate (puree), only move liquids through 'em. Both impeller pumps and diaphragm pumps--manual AND electric--are used for many applications...fresh water pumps, bilge pumps, engine water intake pumps, fuel pumps, toilets and dumping holding tanks overboard.