How to remove a repository

from debian, ubuntu gui you can remove it:

You can easily remove software repositories from the "Ubuntu Software Center"

Open "Ubuntu Software Center"

- Edit Menu
--- Select "Software Sources...", enter your password
----- Select tab "Other Software"

From the "Other Software" tab you can add or remove repositories. 

from debian, ubuntu terminal you can remove it:

sudo add-apt-repository -r ppa:<ppa to remove>

Or, edit the nano /etc/apt/sources.list to find your ppa there, and remove from there manually (or automatically).

Or, remove the ppa file from nano /etc/apt/sources.list.d in newer versions of Ubuntu.

https://askubuntu.com/questions/43345/how-to-remove-a-repository