Formation of linear aldehydes during surface water preozonization and their removal in water treatment in relation to mutagenic activity and sum parameters.

Abstract Low molecular weight aldehydes were formed during surface water preozonization, their levels showing a positive correlation with increasing ozone dose applied and with increasing water temperature. A strong negative correlation was observed between aldehyde levels and U.V. absorbance at 254 nm. Coagulation had no influence on the aldehydes present and the influence of rapid double layer filtration varied strongly with temperature : significant removals were only observed above 10°C. Mutagenic activity generated by preozonization in Salmonella typhimurium TA98 shows an ozone dose depending relationship different from the formation of linear aldehydes. Its removal by coagulation is not effective but rapid double layer filtration reduces mutagenic activity to marginal levels. In this respect too no clear parallel can be drawn between the presence of low molecular weight aldehydes and mutagenic activity.