Coil denitrators work on the principle of anerobic bacterial action.
The bacteria that you are trying to populate in the reactor thrive in an oxygen free environment. Therefore:
- The reactor has to be completely sealed except for the water inlet and water outlet. If there are any leaks that expose the internal water to oxygen, the reactor will not work. The same holds true of the flow rate is too fast, because it introduces oxygen too quickly and stops the bacterial action.
- These reactors are fairly simple and fairly reliable, but their tradeoff is that they take a long time to start up once they are closed up, usually weeks. If you haven't given it at least 3 weeks, no results should be expected yet. The thing is that if your flow rate is too fast, you need to wait several weeks after adjusting it to test for the result.
The result of a reactor not being "cycled" or being oxygenated (due to non-airtight construction or too fast of a flow rate) is effluent with no reduction or higher nitrates. Bring your flow rate down... i'd say to about 1/3 the rate you are at now, and wait at least 3 more weeks before testing for results.