Total Kjeldahl Nitrogen
What it means
The Kjeldahl process measures the amount of nitrogen that a water sample contains in the form of ammonia and in biological forms. The presence of ammonia in the water can be a cause of excessive plant growth which may prove harmful to the health of aquatic ecosystems. While ammonia in water is naturally converted to nitrate, this conversion removes oxygen from the water, which may cause an adverse impact on fish and invertebrates.
How to interpret
While it's difficult to say what a normal Total Kjeldahl Nitrogen (TKN) value is, the higher it is, the more likely you have a problem. Its value is also highly correlated to increased algae blooms, losses in water clarity, and less oxygen in the water.
If you see a spike in this value, or have noticed more plant growth or algae blooms, it could indicate a problem with sewage treatment, agriculture, urban developments, paper plants, industrial waste, recreation, or mining (blasting residuals).