De-Nitrification, does it shut down if NO3 rises too high?

Hi Guys,

It back in the dim and distant past I recall reading somewhere (around a decade ago) words to this effect:

Once nitrate levels have risen above a certain threshold, then the denitrification processes shut down.

Does anyone recall what article it was or by whom it was written? Has there been similar discussions on here? I can't recall if it fitted with my observations over the years or whether it was a bit of a revelation. It does explain certain things I've observed.

I also think the threshold was mentioned to be around 40ppm (mg/l).

Thanks

Chris