Is there a set time / period for internal training's related to 14001? Example our internal waste and recycling training, does it need to be yearly or every three years? etc. Where is that clause or rule located? And for other internal trainings.
No, ISO 14001:2015 does not state any mandatory frequency for training, any kind of training.
Please check clause 7.2 about competence. Competence is what is behind the need for training. If people are competent there is no need for training. For example, if an internal audit raises a non-conformity about errors on waste segregation, it may be a sign of a lack of competence that could be eliminated with training. If your management system has internal rules setting a frequency for training, your organization has to abide by those rules.
The following articles might provide further guidance: