How to manipulate URL in Codeigniter

I want to manipulate URL, the URL like this

http://localhost/project/1/my-stuff

where 1 is id and my-stuff is a slug, I want to change become

http://localhost/project/my-stuff

I try to change the route like this

$route['project/(:any)'] = 'project/$1/$2';

but it doesn't work, the id is very important I cannot delete it, but how to hide id in url, sorry for my english bad.