Separate database credentials for each rails daemon

I'm running multiple worker processes each in their own daemon (with the rails-daemon gem) that should each have separate db roles / privileges (e.g. one should only be able to read table X, the other can write to X and Y), but it seems like Rails is set up to read the db credentials from one config/database.yml. How do I set up configure multiple db users in rails so that each worker uses its own credentials?