Bernard,
When you state working 'in' a treatment plant do you mean as an engineer or operator and as a consultant or for the utility that owns the plant?
If Indiana is like South Carolina, there are no special licensure for a PE that is doing engineering at the treatment plant (consulting or at the utility) other than being competent in the field if you are stamping anything. My utility does require our in house engineers to have a level A operators license for water or wastewater depending on which plant they work at, but that is a requirement by our company not the state.
Best thing to do is inquiry with your state licensing board to verify requirements.
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James Wilson P.E., M.ASCE
Engineer
Charleston Water System
Charleston SC
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