Almost all scrubbers are open loop, which means the sulphur is discharged into the water. It is much cheaper than storing it onboard and discharging to shore. Scrubbers come in many different designs, where some are small and other (like here) huge. You would not be able to tell from the outside whether it was one or the other, as far as I know, but I doubt there are VLCCs with closed loop scrubbers.