With increasing liability concerns surrounding cooling water pathogens, more water treatment companies are incorporating oxidizing microbicides as the mainstay of their cooling water biofilm control programs. Chlorine and bromine chemistries are used extensively for this purpose. Both chlorine and bromine containing compounds come in a variety of forms including gas, liquid, and solid forms all offering different features and advantages with regard to safety, cost, and efficacy.

The purpose of this technical paper is not to review the various characteristics of or provide an extensive comparative efficacy study of these oxidant forms, but to help provide insight into the question of whether bromination offers a significant advantage over chlorination and if chlorination can still be an effective method for microbial control in cooling water systems operating at high pH. This paper will attempt to answer the questions posed by including discussions based on observation, experience, field test data on five operating cooling water systems, and laboratory data.