How to manage trash cans for a triplex

[Jeffrey Duck]

My triplex has a ~6'x8' enclosed area for trash cans (55 gallon rolling receptacles). Each unit has one for trash and one for recycling so there are six in total. The cans need to be rolled to the curb twice a week and the city limits the time they can be out, from the evening before pickup, to the night of pickup. 

Currently, I lease one of the three units to someone who keeps it clean. He's someone I already knew, and he does the work for a small rent discount but he's about to move out and I don't think it'll be so easy to find another qualified tenant without losing a month's rent while looking.

Before I bought the building, the tenants were all responsible for taking their own cans to the road and they were collectively responsible for keeping the area clean, but they didn't (and I didn't know they didn't.) After I bought it, I learned that the owner, who lived close by would take the cans to the road and clean up the area. In reality tenants would use each other's cans so they wouldn't have to take theirs out, OR for retribution, because another tenant used their cans. Also, there was regularly raw garbage or trash bags left sitting on the ground. 

How can I keep the area clean and the tenants happy at a minimal cost?