Determination of ammonia levels in water and wastewater with an ammonia probe

Abstract

The application of an ammonia probe has been investigated for discrete laboratory measurement of ammonia levels in a variety of waters. The probe displays a Nernstian response for the range 0·2 to 40 mg l^–1 of ammoniacal nitrogen in a stirred 0·1 M sodium hydroxide solution containing 0·01 M ethyl-enediaminetetraacetic acid. Recoveries of added ammonia from a wide range of water samples are satisfactory. Both these recoveries of added ammonia and repeated calibrations of the probe suggest a precision of 4 per cent. for ammoniacal nitrogen concentrations greater than 0·4 mg l^–1 and 0·015 mg l^–1 for concentrations less than 0·4 mg l^–1; the statistical limit of detection is 0·03 mg l^–1. Good agreement is obtained with existing methods based on distillation and spectrophotometric measurement for a further range of samples, but the limit of detection and the precision at low levels suggest that accurate determination in potable waters would be difficult.

The probe can also be used to determine albuminoid nitrogen by taking the difference between the ammoniacal nitrogen and the total free plus albuminoid nitrogen obtained by distillation. Values obtained in this way agree with those obtained by existing methods subject to the precision of the probe being acceptable.