A water treatment system for reducing the level of bacteria in a flow of water by creating an environment favorable for aerobic bacteria and unfavorable for anaerobic bacteria is disclosed. The system may include a method including intaking a flow of water, lowering a pH level of the flow of water to a predetermined range of pH levels, and adding sodium chlorite to the flow of water after lowering the pH level to the predetermined range of pH levels for producing chlorine dioxide. The sodium chlorite is added in an amount sufficient to produce a residual amount of sodium chlorite that does not produce chlorine dioxide, and the flow of water is outputted to the point of use with a residual amount of chlorine dioxide. The system may include an apparatus for carrying out the method of the invention.