NIR monitoring of ammonia in anaerobic digesters using a diffuse reflectance probe

The feasibility of using a diffuse reflectance probe attached to a near infrared spectrometer to monitor the total ammonia nitrogen (TAN) content in an anaerobic digester run on cattle manure was investigated; as a previous study has indicated that this probe can be easily attached to an anaerobic digester. Multivariate modelling techniques such as partial least squares regression and interval partial least squares methods were used to build models. Various data pre-treatments were applied to improve the models. The TAN concentrations measured were in the range of 1.5 to 5.5 g/L. An R(2) of 0.91 with an RMSEP of 0.32 was obtained implying that the probe could be used for monitoring and screening purposes.