On Mac if you want to delete the files from Trash then just Cmd + click on it and select the option Empty Trash and it asks to confirm either you want to Empty Trash or not.
The process to empty the Trash is simple and you think that in this way your Trash is securely empty but actually those deleted files still exist on Mac hard disk until these will be overwritten by any other deleted files. It means the files which are deleted from Trash could be recovered through any recovery tool.
So, if you want to permanently and quickly delete your files from Mac OS X and do not want to send them in Trash then there is an option available Empty Trash Securely. The tip to do that is very simple and could be used in two different ways which are written in follows.
Press Cmd+Shift+ Click on Trash and select Secure Empty Trash option
It prompt to confirm the deletion process so click on Secure Empty Trash button and it will start deleting items permanently from Trash.
You may also set your Mac to always Secure Empty Trash. To enable this option permanently you may adapt the following method.
Click on Finder
Go to Finder menu >> Preferences
Click Advanced icon and mark the check box besides Empty Trash securely and close the screen
Now Cmd + Click on Trash and observe the change what you made.