NTOTAL - What is Total Nitrogen?

Total Nitrogen or Total Kjeldahl Nitrogen (TKN) is the U.S. EPA approved parameter, used to measure organic nitrogen and ammonia. Total nitrogen is the sum of Total Kjeldahl Nitrogen (ammonia, organic and reduced nitrogen) and nitrate-nitrite. It can be derived by monitoring for organic nitrogen compounds, free-ammonia, and nitrate-nitrite individually and adding the components together. The TKN content of influent municipal waste-water is typically between 35 and 60 mg/L.

Since the measurement of Total Kjeldahl Nitrogen is performed using a laboratory apparatus and is not suitable for on-line measurement, alternative techniques to determine total nitrogen are required for process control applications.

However, total nitrogen may be determined using discrete on-line instrumentation. The Proam ammonia monitor provides continuous on-line measurement of the ammoniacal-nitrogen using a gas sensing, ion selective technique. Automatic calibration and chemical cleaning provide measurement assurance. The summation of nitrate and nitrite may be determined optically by using UV spectral analysis. The optical probe technology is typically configured to measure on an interval from 5 minutes but the interval may be adjusted to suit the application requirements. The NICO sensor reports a combined NOx concentration (summation of NO3 and NO2) or alternatively the OPUS sensor has the capability to report the nitrate and nitrite concentrations individually. Automatic compressed air cleaning of the optical windows improves measurement reliability especially for measurement applications containing significant bio-solids.