This plugin will convert ISO-8859-1 data to UTF-8 data in a MySQL UTF-8 WordPress database where things at some stage went wrong – this can happen during a command line backup/restore batch if your shell is misconfigured, for instance.
Install the ISO to UTF content plugin and you can with a few clicks
in the WordPress admin panel convert all ISO-8859-1 data to UTF-8 data. You will also
have the option to exclude columns in tables you do not wish to run the conversion on.