Spectrophotometric Determination of Bromide in Cooling Water of Electric Power Stations

Bromine based biocides are widely used in cooling water systems of electric power plants as they are more efficient against biofouling of pipelines than chlorine based ones. Cooling water usually consists of river water spiked with sodium bromide, later certain amount of hypochlorite is added to convert bromide into bromine. Control of bromide levels should be accomplished to ensure its proper concentration in water. A number of spectrophotometric methods of bromide determination were tested for analysis of cooling water which may contain chlorides, iodides and boric acid as interfering substances. Standard Phenol Red method was found to be inappropriate due to interference from borate. Procedure based on BrCl formation did not give reliable results because of volatility of BrCl compound. Direct detection of bromide based on its self-absorption in UV region suffers from interference of other compounds which demonstrate absorption in the same spectral range. Method which includes triiodide ion formation was found to be most convenient. Cooling water of electric power station was analyzed for bromide using this method and ICP-MS method. Good agreement of results permits to recommend the method of triiodide formation for control of bromide content in waters intended for use in cooling circuits of nuclear power plants.