Abstract
Experiments on disinfection by chlorination, ozonation and ultraviolet-irradiation methods were performed with secondary effluents from domestic wastewater treatment plants, independently. Each treated water sample was evaluated for mutagenicity by the sensitive Ames test. Chlorinated water samples had a high mutagenic activity (the maximum average was 7,120 net rev·l-1 when 50mg·l-1 chlorine was used), depending on chlorine dose. Ozonated water samples and ultraviolet-irradiated water samples showed no or low mutagenicity. Even under good treatment conditions for each method, chlorinated effluents had a strong mutagenicity, but ozonated effluents and ultraviolet-irradiated effluents had a mutagenicity of almost zero.
