Why is the pH rising in my nitrifying bioreactor?

[K N and P J Harris]

Hello,
I suspect that the problem is air stripping of "excess" carbonate for 
the high level of calcium carbonate you report. Nitrifiers always (in my 
experience) take a while to get going. The system WILL acidify but only 
when the population has built up to a fully functional level.
Try running the medium in a chemostat without organisms and see how the 
pH behaves in relation to various air stripping rates.
We had a problem here at Reading many years ago with a cattle slurry 
effluent system which was aerated but to which we added the slurry 
effluent too quickly. The ammonia raised the pH so quickly (before the 
nitrifiers "got going") that we had the classic ammonia toxicity effect 
and were producing an effluent with 400 ppm nitrite-N for our local 
river ! NOT a good idea.

Tot ziens

Dr Peter Harris,
AKA <P.J.Harris at reading.ac.uk>
Department of Soil Science ,
The University of Reading,
U.K.