Water purification research. Laboratory research microbiologists testing water purification reactions. They are testing the effects of chlorine dioxide on the removal of iron and manganese in water, and the use of chlorine dioxide (instead of chlorine) to eliminate the risks of excessive THMs (trihalomethanes) and bromates in heavily chlorinated water. Chlorine dioxide (ClO2) is used as both a disinfectant and an oxidiser in water treatment processes. This research is being carried out by the Scotmas company in Scotland. Photographed in 2016.