Bulk deletion of users


I'm taking over the main administration of the domain for the college I work in, I've come across over 14,500 inactive accounts from the last 6/7/8/? years and want to delete them.

These accounts are under the main tree but under different OU's so I'm not sure it's a simple task. 

I do have a CSV of all the usernames so was hoping there was an easy way to use this.

I've looked through the JRBUtils hoping for a nice tool to help but no luck.

Can anyone point me in the right direction for bulk deleting users across multiple OU's?