The on-line measurement of ammonia to determine ammoniacal-nitrogen concentrations is an established, well proven technology extensively employed throughout the water and waste industry. The parameter is a useful indicator of water quality indicating the presence of partially treated waste-water and the possible presence of pathogens. Ammoniacal-nitrogen is also harmful to aquatic life and this parameter is therefore widely installed for discharge compliance monitoring.

Ammoniacal-nitrogen can be determined in several ways but in principle two methodologies predominate; colormetric and ion selective electrodes (ISE). Colormetric techniques use a reagent to produce a colour change proportional to concentration which is then measured photometrically. ISE techniques fall into two categories; direct ammonium determination which has limited application and a much more precise technique using a gas sensitive ammonia ISE requiring pH adjustment of the sample.

Pollution and Process Monitoring have optimised the ammonia ISE methodology for on-line measurement of ammoniacal-nitrogen. The ProAm is a hybrid of many other designs packaging the technology in a simple, compact format and addressing the common pitfalls associated with other products. The ProAm uses large diameter tubing to deliver the sample to a reaction vessel where the pH is adjusted. No sample preparation is required for applications containing solids to 200mg/l (intake protection and final effluent monitoring) removing an un-necessary point of blockage, reducing maintenance and installation costs. To ensure operational reliability, automatic chemically cleaning can be used to removed chemical and biological contaminants at a frequency to suit the application. Internally, pinch valve technology is used to reliably deliver the sample, calibration standards and cleaning fluids which pass through a heat exchanger to regulate temperature ensuring good reproducibility. The technique can be run continuously without interference from suspended solids although intermittent analysis may also be selected to further minimise reagent consumption.