cleanup of pg_temp schemas

Hi all,

My PostgreSQL app uses temporary tables. After some time, my database shows lots of pg_temp_xxx schemas with no data
inside.I tried to do a vacuum full analyze to get rid of them, but they still persisted. 

Who takes care for removing these schemas? Can I safely ignore them, or do I have to clean them up periodically? How
shouldthis be done preferably? 

Any help would very much be appreciated.

Regards
--Marcel