Preliminary toxicity assessment of water after treatment with UV-irradiation and UVC/H2O2

Photooxidation (UV radiation) and enhanced photooxidation. (UVC/H2O2) are w ater treatment technologies which remove aquatic natural organic matter (NO M) by photodegradation, producing lower molecular weight components and CO2 . Since these technologies are being investigated for the treatment of drin king water, knowledge of the potential toxicity of the photooxidation by-pr oducts is vital. The potential toxicity of UVA-, UVB-, UVC-irradiated, and UVC/H2O2-treated aquatic NOM in two spot samples from two Australian reserv oirs was analysed in two spot samples using Vibrio fischceri in the Microto x(TM) test, African green monkey kidney cells (AS/NZS 4020:1999), and Daphn ia Carinata in an acute immobilisation test. Toxicity was not apparent for both the Microtox(TM) procedure and cytotoxicity analyses for the UVC-irrad iated and UVC/H2O2-treated NOM samples, while UVA- and UVB-irradiated water samples were non-toxic to D. carinata. In contrast, acute toxicity was obs erved for UVC- and UVC/H2O2-treated water samples. The observed toxicity wa s attributed to photooxidative degradation of NOM-metal binding sites, whic h resulted in the release of bioavailable copper ions, as evidenced by high er concentrations of free copper ions in photooxidised water. As the total copper concentrations of the two raw water samples were well below the Aust ralian Water Quality Guidelines for metals in domestic supplies, the releas e of copper from photooxidised NOM is unlikely to cause health concerns in these samples. (C) 2001 Elsevier Science Ltd. All rights reserved.