Oxidation / Desinfection

Team
Urs von Gunten, Lisa Salhi, Maaike Ramseier

Goal
Assessment of disinfection and oxidation processes.

Description
Disinfection and oxidation processes have been applied in drinking water treatment for the last hundred years. Whereas the disinfection was the primary application of chlorine, ozone has been applied for disinfection and oxidation purposes. Ozone is a very selective oxidant that mainly reacts with activated aromatic systems, amines and double bonds. Some of the important compounds for which ozone can be applied in drinking water treatment are color (NOM), taste and odorous compounds, algal toxins, estrogenes (phenolic entities), antibiotics (amines) and other pharmaceuticals, ethenes (double bonds). An additional feature of ozone is the formation of OH radicals which can be used to oxidize micropollutants (advanced oxidation processes).

If ozone is incorporated into a treatment train the oxidation of NOM leads to the formation of AOC (assimilable organic carbon). This is crucial for the subsequent processes because it will lead to an increased microbial growth and may alter the performance of these processes. Even though there is information available on the nature of the compounds which are responsible for AOC, the mechanisms and kinetics of their formation is not well established. To optimize oxidation and disinfection it is therefore necessary to relate the beneficial effects to the undesired formation of AOC.

The effect of oxidation processes on fractions of NOM, specific microbial species (e.g. algae and cyanobacteria), and selected environmental chemicals with respect to the re-growth of heterotrophic microbes are investigated.