What is difference between Clean Ballast and Segregated Ballast Tanks?

Clean ballast:-

It means the ballast in a tank which since oil was last carried therein, has been so cleaned that effluent there form if it were discharged from a ship which is stationary into clean calm water on a clear day would not produce visible farces of oil on the surface of the water or on the adjoining shore Line.

Segregated Ballast:-

It means the ballast water introduced into a tank which is completely segregated from the cargo oil and oil fuel system & which is permanently allocated to the carriage of ballast or to cargos other than oil & Noxious Liquid substances.