Removing discolouration from water can be really tricky. However, ozone is very effective at removing it from (waste) water. Discolouration is mostly caused by dissolved chemicals like fulvic acids, tannic acids, humic acids or hydrocarbons, or by suspended particles. Ozone can easily solve all of this. Ozone is a very strong oxidizer and removes discolouration without forming chlorinated organic compounds. An ozone dose of 1 mg/l can, on average, cause a reduction of 10 colour units (Pt/Co scale).
Ozone can also be used as a bleaching agent to bleach paper or laundry for example. Chlorine is mostly used for this purpose but ozone is a good, environmental friendly alternative.