ASSESSMENT OF AN AMPEROMETRIC MEMBRANE PROBE FOR DETERMINING FREE RESIDUAL CHLORINE IN SALINE COOLING WATERS

Cooling water at coastal and estuarine power stations is chlorinated to inhibit mussel growth in the intakes to the condensers and a means of automatically monitoring the free residual chlorine concentration is desired so that the dosage can be precisely maintained at 0.2 μg ml-1 Cl2. The Delta Scientific model 82124 amperometric membrane probe has been tested in the laboratory for its suitability for this application. The probe had a linear response to hypochlorous acid over the range 0-5 μg ml-1, but was not specific for free residual chlorine, as chloramines also produced a response. The main product of the chlorination of sea water is bromine, to which the probe is about five times more sensitive than to hypochlorous acid. Although the probe can be calibrated with bromine, its response is then much noisier than that obtained with hypochlorous acid. The salinity of the sample influences the reading obtained at a given concentration of oxidant: increasing the salinity increases the reading obtained with hypochlorous acid but decreases that obtained with bromine. © 1979.