Chlorination of Sea Water containing Ammonia Nitrogen

Abstract

In order to elucidate the behavior of chlorine in sea water, the chlorination and bromination of artificial sea water containing ammonia nitrogen were made. The concentration of residual oxidants (CRO) after chlorination for one hour increased proportionally with increasing the concentration of chlorine added, and reached to the maximum point (MP). The molar ratio of ammonia nitrogen versus chlorine at MP varied in the range of 1 : 0.87 to 1 : 1.29 with the concentration of ammonia nitrogen (0.7-2.8 mg/l). CRO decreased above MP, and arrived the minimum at the molar ratio of 1 : 2.5. The ammonia nitrogen almost disappeared. This ratio was considered to be the break point (BP). Monochloramine comprised much of the oxidants below BP, while free bromine was dominant above BP. In the bromination of artificial sea water, the molar ratio of BP was similar to that in the chlorination. However, the concentration of residual bromine after bromination for one hour below BP did not increase with increasing the concentration of bromine added, and MP was not observed. Below BP, monobromamine decreased rapidly with time and tribromamine only remained after one hour. The reaction of ammonia nitrogen with bromine was more rapid than chlorine. A similar behavior was observed in natural sea water containing ammonia nitrogen.