In this article, the wastewater treatment by UV oxidation with and without preceding desalination is compared. The influence of different chloride concentrations on the TOC degradation and AOX concentration is analyzed. Nanofiltration membrane dialysis is used to separate the chloride ions from wastewater. It is demonstrated that a reduction of the chloride concentration leads to a faster TOC degradation compared to the treatment of non-desalinated wastewater. Furthermore, the additional formation of AOX during the process could be avoided in effect leading to a significant degradation of native AOX.