Growing bacteria in a petri dish takes between 3 to 7 days depending on the type of bacteria you're growing in the petri dish.
Some bacteria types grow in petri dishes faster than other bacteria.
But you should notice your bacteria in the petri dish growing within 3 to 7 days.
To dispose of petri dish bacteria kill the bacteria in the petri dish with some household bleach and then place the petri dish directly into the trash to dispose of it.
To dispose of petri dishes after using them for bacteria you need to kill the bacteria that you grew in the petri dishes.
To kill off bacteria that you grew in the petri dish you take some household bleach and pour some bleach into the petri dish.
The bleach will kill the bacteria that was grown in the petri dish making it safe to dispose of in the trash.
So after you kill the bacteria in the petri dish with bleach then put the petri dish into a bag such as a grocery bag and tie it closed.
Then just dispose of the petri dish into your normal trash but always make sure you kill the bacteria in the petri dish first so that the bacteria doesn't spread.