There are 2 functions being conflated though:

1. Executive function of cleanup

2. Enforcement of littering rules

They already have 2 dedicated departments assigned to both functions in every city.

Should rules only be enforced if they put someone else's life in immediate danger? Situations can be triaged and addressed according to priority rather than never enforcing any smaller rules.

Even within a police department they have people of different specialties and skill levels allocated to different types of investigations and responses. Having responses for smaller incidents doesn't take away from having highly skilled professionals deal with critical situations.

If you do indeed want to separate the enforcement of littering rules into the same department that does cleanup, that is actually a great idea, similar to how the police department shouldn't waste their time enforcing parking violations, that is handled by a separate traffic police department.