How to revoke privileged from PostgreSQL's superuser

[bejita0409]

Hello,
 
I am a newbie DBA.
 
I have a request for revoking the access to user's data from DBA-user.
I think the request is right because users should be the only ones can access 
their data.
But DBA-user also need full access to the other data? It means that DBA-user 
also needs to be a superuser.
 
So I conclude the request that how to revoke privileged from superuser in 
postgres.
 
As my knowledge, the superuser in PostgreSQL bypasses all the permission check.
So that, there is no way to do it in PostgreSQL, is that right?
 
Is there some DBAs are faced with this before?
 
 
Thanks,
--
bejita