ABSTRACT
Phosphorus occurs in wastewater almost entirely in the form of phosphates including orthophosphates, condensed phosphates and organically bound phosphates. The diverse methods of detection do not all respond to the total phosphorus present. The principal application of a phosphorus analyzer is the control of phosphate removal in a sewage treatment plant. In the commonly used aminonaphtholsulfonic acid method, ammonium molybdate reacts with a dilute phosphorus solution to produce molybdophosphoric acid, which is reduced to the intensely colored complex, molybdenum blue, by the combination of aminonaphtholsulfonic acid and sulfite reducing agents. This analyzer detects the photometric flame emission of phosphorus compounds in a hydrogen-air flame. Where elemental phosphorus discharges into water, it has been found that a concentration of a few parts per billion is lethal to fish. The successful application of the phosphorus analyzers just described depends on reliable delivery of a well-filtered sample.
