@ZipLine-- Is he going to have his gallbladder removed?
I hope the taste of bile disappears after that. In my case, it was just the opposite. I developed the bile taste in my mouth after my gallbladder removal surgery. My doctor said that the bile taste will slowly go away and it did. So if your dad continues to have this issue for a while after the surgery, don't be surprised. Chewing gum helps get rid of the taste.