Chlorine and bromine solutions were tested to see which is better at killing bacteria in different types of water. Bromine worked best in water with lots of nitrogen, while chlorine was better in water with less nitrogen. Mixing chlorine and bromine together made them more effective, especially when there was less hypobromite. Bacteria that survived chlorine exposure became resistant, but adding a little bromine made them sensitive again. The two disinfectants work together to kill bacteria. Some resistant bacteria changed into slower-growing organisms.