I think your imagination is much worse than reality. While your home laundry is arguably questionable (a lot of the sterilization occurs in the drier!) industrial laundry is a different ballgame altogether. How do you think hospital bedding gets cleaned? Most if not all industrial laundromats do regular testing of cleaned items to test for bacteria, organic matter, etc.

A nappy service is very likely to do a much better job than you'd do at home.