ONLINE FLOW-INJECTION MONITORING OF AMMONIA IN INDUSTRIAL LIQUID EFFLUENTS

A flow-injection method was applied to on-line analysis for ammonia in industrial liquid effluents. The method utilised the diffusion of gas eous ammonia from an alkaline sample stream, through a microporous mem brane, into a bromothymol blue indicator stream, with the resulting co lour change measured photometrically using a red LED. Following initia l development work, the method was adapted to an automated, portable s ystem, which was capable of linear response in the range 1-100 mg l(-1 ) NH3-N. The portable flow injection monitor was powered by an externa l 12 V battery, and performed two-point self-calibration during each a nalytical cycle. The monitor was capable of unattended, continuous on- line monitoring of effluent streams at two industrial sites over sever al days. The results obtained were in good agreement with those produc ed by an indophenol blue laboratory reference method.