Bromine and Bromamine Disinfection Chemistry

The chemistry of bromine as a water disinfectant is analyzed. A logarithmic pH versus bromine-ammonia mole ratio distribution diagram for bromine and the bromamines is presented for 10^-4 M aqueous bromine solutions. Ultraviolet absorption spectra were used to identify the principal bromamine species initially formed as well as to follow the apparent second and third order decomposition of dibromamine and tribromamine, respectively. In the neutral pH range, tribromamine forms in solutions with mole ratios of ammonia to bromine less than 2:3 while dibromamine occurs at ratios greater than 2:3. A mechanism is proposed which accounts for the rapid rates of decomposition between dibromamine and tribromamine in the breakpoint region. Known variations of sporicidal and virucidal efficiencies as a function of pH, time and ammonia to bromine ratios are correlated with changes in the chemical species in solution.