Hi.
For "Bilge" refers to the lowest-most parts of an inside of the ship, where a mixture of liquid, semisolid and solid remains end up, specifically from the motor like oil, lubricants, water antifreeze chemicals etc. Also see https://en.wikipedia.org/wiki/Bilge and https://www.leesan.com/shop/leestrom-ls60b-bilge-water-pump-station.aspx

These kind of pumping stations are extremely important infrastructure for sailors. Most times, they are combined with grey or black waste water stations. Grey (so kitchen sink/dishwasher) and black (toilet) water are usually not differentiated in this context.