Purifying our drinking water removes the bacteria that can make us sick. It can also introduce some harmful chemicals too.
The most common water purification techniques are very efficient in removing biological and heavy metal contamination. The drawback, excessive chlorination can produce high levels of highly carcinogenic chlorinated hydrocarbons.
Similarly, ozonification can lead to high levels of bromate. These highly carcinogenic oxyhalides are defined as disinfection by-products.
Disinfection by-products, at a ppb levels, are closely monitored by the EPA as an important part of drinking water analysis. Ion chromatography is the preferred technique, providing clear quantification at very low detection limits.