A part of volatile materials in make-up seawater has possibility of transferring into fresh waterin a distillation process. Ammonia is one of such pollutants. The present paper is concernedwith both fundamental study in laboratory and field tests with a test plant on decomposition ofammonia by chlorine treatment of make-up seawater in a multi-stage flash plant.
In the fundamental study, effects of reaction temperature, chlorine amount added and pH ondecomposition rate of ammonia were measured. It was found that increases in chlorine added andhigher temperatures promoted ammonia decomposition. It was also observed that the presence ofbromide ion accelerated the decomposition. The higher the pH value in the sample was, thefaster ammonia decomposed. It was suggested from the results that one should add chlorinebefore acid injection for a pH-controlled desalination plant.
In the field tests with a 100,000m3/day test module, 0.4 or 0.7ppm ammonium ion was addedto the intake seawater, and decomposed by 3ppm chlorine.The experiments showed that 3 ppm chlorine was sufficient for 0.4 ppm ammonium ion, but not for 0.7 ppm.
