Evaluation of the Effect of Using the UV + O3 Process with Low- and Medium-Pressure Lamps on the Amount and Properties of Organic Substances in Treated Water

The application of oxidation processes, including advanced oxidation, in water treatment is one of the effective methods for eliminating risks associated with the presence of organic substances in water and those formed during chlorination. This article presents the impact of advanced oxidation in the UV + O3 process on the content and structure of organic substances present in three natural waters with different levels of total organic carbon (TOC). The process was carried out using low-pressure and medium-pressure lamps with an irradiation time of 40 min and ozone doses of 1.5 gO₃/m3 and 5 gO3/m3. Advanced oxidation, regardless of the type of lamp used or the ozone dose, had the greatest effect on the content of humic acids, which underwent both transformation and mineralization. The use of a low-pressure lamp resulted in an increase in the content of organic substances with the lowest molecular weight (<0.7 kDa), whereas the medium-pressure lamp led to an increase in substances with a molecular weight >1.3 kDa. Regardless of the ozone dose and the type of lamp used, the transformation of organic substances dominated over mineralization, whose efficiency reached a maximum of 44.9% and 38.4% for the low-pressure and medium-pressure lamps, respectively. The degree of organic substance transformation and the efficiency of their removal were directly proportional to the TOC content in the raw water. The use of a low-pressure UV lamp ensured higher process efficiency, which is also associated with lower energy costs.