Background and objectives:Pre-ozonation in water treatment is used for various purposes such as; improving the coagulation process, reducing the production of trihalomethanes, color removal, removal of iron and manganese, control of microorganisms, and removal of organic matter. The main objective of this paper is to investigate the effects of pre-ozonation on the physical, chemical, and biological properties of drinking water.

Methods:This study on a real scale was conducted on the pre-ozonation unit of the Koohsabz drinking water treatment plant for 6 months. In this study, sampling of raw water entering the pre-ozonation unit and ozonized water was done randomly with glass sampling containers. 4 samples per month and a total of 24 samples were taken to evaluate the trends of changes in the parameters. The necessary tests according to the method presented in the standard method book (twentieth edition) on the samples have been done to investigate the effects of pre-ozonation on the physicochemical and biological parameters.

Results: The studies showed that the turbidity and TOC (Total Organic Carbon) removal efficiency in the pre-ozonation process of the Koohsabz drinking water treatment plant was about 62% and 18. 83%, respectively, and it has no effect on pH. Also, the removal rate of Fe and Mn in the pre-ozonation process was 91.5 and 82%, respectively. Evaluate the effectiveness of pre-ozonation in watercolor removal showed that, by increasing the dosage and the concentration of ozone injection, significant changes did not occur on further reduction of color and color precursors and the removal rate of color precursor compounds, such as the chlorophyll a, is about 21%.

Conclusion:The results indicated that ozone could not change any physical parameters such as pH and color, but it has a significant effect on the chemical properties and reduced biological parameters by about 21%.