Different types of Ballast water exchange

Sequential:

In this method the ballast tanks are emptied until the ballast pumps lose suction and then the tanks are further stripped by eductor systems. This is followed by taking fresh ballast into the tank.

Flow through method: 

In this method water in pumped into the tank and to allow it to overflow through the air vent or dedicated overflow vents. Three times the volume of the tank is to be pumped through to get a 95 percent efficiency of exchange.

Dilution Method: 

In this method the tank has two openings; water is pumped in from one opening and flows out through the other.