In the US there is a push ...

In the US there is a push for Professional Operator Certification (PO) that would be valid across States, but I don't know of States that have signed on. This would require working in a plant as an operator.

Since you are an engineer, becoming a Professional Engineer (PE) may be more of what you are looking for. Don't know what this requires.

I would look at the Association of Board Certification (ABC) and the Water Environment Federation for better information.

Mark