One alarm per waste type
Set general waste to repeat every Monday and Thursday, recycling to its own day, garden waste to another. Each is a separate alarm with its own title, so the notification tells you which bin rather than just that something is due.
Fortnightly and 2nd-and-4th collections
Alternate-week collections use the biweekly repeat, counted from the date you set. Collections on the second and fourth Wednesday are two alarms using the nth-weekday repeat. For a month-end collection, "last Wednesday of the month" never drifts in months with five Wednesdays.
The night before is the useful alert
A pre-alert the previous evening is worth more than one on the morning itself, because the evening is when you can actually bag things up and put them by the door. Pre-alerts run from 5 minutes to a week ahead, so pick whatever fits your routine.
Still audible on a silent phone
Phones are often left on silent overnight. CAlarm alarms go through AlarmKit and ring anyway at ringer volume, so an early collection does not depend on remembering to unmute.
Put it where you will see it on the way out
Collections are easy to know about and still miss. A widget on the Home Screen shows what is coming next, and because it lists from the current time forward rather than by calendar day, a 6am collection is still on screen when you check the phone the night before.