What is PostgreSQL database ownership When creating a PostgreSQL database one can assign another role to be an owner of that database. What can the new owner do with this database? How is it compared to grants?
When an object is created, it is assigned an owner. The owner is
normally the role that executed the creation statement. For most kinds
of objects, the initial state is that only the owner (or a superuser)
can do anything with the object. To allow other roles to use it,
privileges must be granted.
The right to modify or destroy an object is always the privilege of the owner only.

http://www.postgresql.org/docs/current/static/ddl-priv.html