Maintenance Free Ammonia Measurement

Measurement Technique: A Unique Method UV-Vis Spectroscopy after gas stripping

Tethys Instruments SAS’ online ammonia analysers have been widely used for industrial and municipal waste water applications for many years. Tethys ammonia measurement is based on UV absorption of ammonia gas after a stripping phase. NH4 is converted in to its gas phase by addition of NaOH. NH4 is measured in the gas phase through the UV Absorption spectroscopy principal. Consequently, the turbidity or colour of the sample has absolutely no influence and measurements can even be carried on activated sludge. It gives exceptionally selective measurements for ammonia without any drift as an automatic zero is performed on each measurement on ambient air. The ammonia gas has a typical periodic absorption spectrum that is analysed using a Fast Fourier Transform (FFT) that brings exceptional selectivity. No interference has ever been reported after years of operation on many different applications.

Operators have reliably used Tethys’ analysers as they perform ammonia measurement without interference from other ions present in the sample. The instruments have a narrow spectrum bandwidth hence they carry out completely interference free measurement. With completely drift free measurement, span calibration is not usually required after a long period of time. Tethy’s analysers’ also feature an auto zero calibration facility ensure drift free measurement The analyser’s patented flow cell allows operation even with very high level of suspended solid without clogging. No filtration is required on a majority of waste water applications. Maintenance can be simplified with an optional auto cleaning facility and the sample does not make direct contact with the detector or light source. A multi parameter unit can be configured to measure other properties such as NH4, COD, BOD, pH, TSS, NO3 and PO4.