Treatment: improvement or deterioration of water quality?

The formation of trihalomethanes through chlorination has shown very clearly that water treatment processes may adversely affect water quality. There are many more examples of such effects, including the following which are discussed in detail: 1. Formation of organohalogen compounds in addition to trihalomethanes by chlorination and other oxidation processes. 2. Formation of more polar, more biodegradable organics by ozonation for example, and the consequent increase in bacterial growth in the distribution system. 3. Formation and removal of organic and inorganic corrosion inhibitors by treatment, and the consequent higher heavy metal concentrations in tap water.