The bactericidal efficiencies of chloramines produced by (1) concurrent addition of chlorine and ammonia to the influent water, (2) prechlorination followed by addition of ammonia, and (3) preammoniation were compared with that of free residual chlorine during pilot testing. Coliform bacteria were found to be a poor indicator of the relative ability of the application schemes to disinfect water. Concurrent chlorine and ammonia application, prechlorination followed by addition of ammonia, and free residual chlorination generally produced low total bacteria counts in the pilot‐plant effluent. Preammoniation resulted in the highest frequency of elevated total bacteria counts (1 colony‐forming unit/mL) in the plant effluent.