Water stripping from tanker oil sludge?

An oil tanker has 2 sources of oil sludge or waste. The tanks and the engine room.

In the oil tanks the residue after tank cleaning gets pumped into the slop tanks which are 2 tanks usually the last 2 tanks on the cargo deck.

They are specially constructed with heating and has a shape which make them easy to pump down.

after all the residue has been pumped into the slop tanks they will be heated up and that will help the separation of oil and water. when a water layer has been measured under the oil the water will get pumped out. during this pumping a sample of water will continually get measured for oil content. The measurement is getting performed by ODME (Oil Discharge Monitoring Equipment) and if the measurement is higher than 15 PPM (Parts Per Million) the valves will automatically close and bypass the overboard discharge.

The left over sludge or slop will be send to a plant ashore for burning.