If you already have a custom recovery (ClockworkMod or TWRP) installed then you should be able to flash the Superuser recovery zip which will remove any other binaries/files related to other superuser apps in the process.
The SuperSu app may still be installed but you can un-install that yourself as you would any other app.
Quote from Superuser play store description:
Manual installation with the recovery zip:
Recommended if you are having installation issues or are not rooted http://download.clockworkmod.com/superuser/superuser.zip