There are many ways to "glitch" an image, but to achieve what you want (the jpeg artifacting / loss of quality) all you need is time (or a script!).
There are numerous examples online showing deterioration of jpg files by exporting it excessive amount of times. Exporting is the key factor here. This way you are not just saving a copy of the image, but ...
You can corrupt/glitch an image yourself. All you need is a text editor.
Open the image in a text editor, such as Notepad++
Scroll down the code a bit to get away from the header code, and copy a few lines of code.
Scroll to a different location, highlight a few lines of code, and paste the code you copied, to replace it.
Repeat step 3 several times.
I'm guessing the project is over, but in the interest of adding to the discussion - open the image in a text editor, remove text, add mashed keyboard text, copy text from somewhere else.... save then open in an image editor. Australian photographer Mike Gray does this very well. http://mikegrayphoto.net/#cbp=ajax/post2.html