Personally I would not call what is in that pipe 'water'.
250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe.
250.104(B) Other Metal Piping. Where installed in or attached to a building or structure, metal piping system(s), including gas piping, that may become energized shall be bonded.....
Do you think the waste pipe may become energized?
I think that would take very unusual circumstances.