Biodegradability and toxicity assessment of trans-chlordane photochemical treatment

The removal of trans-chlordane (C10H6Cl8) from aqueous solutions was studied using UV, UV/H2O2, UV/H2O2/Fe2+, UV/TiO2, or UV/TiO2/H2O2 treatment using either UV/Vis blue lamps or UVC lamps (254 nm). H2O2, FeSO4 and TiO2 were added at 1700, 456, and 2500 mg L−1, respectively. trans-Chlordane was not significantly removed in non-irradiated controls and in samples irradiated with UV/Vis. It was also not removed in the absence of surfactant Triton X-114 added at 250 mg L−1. In the presence of the surfactant, trans-chlordane concentration was reduced by 95–100% after 48 h of UVC and UVC/H2O2 treatments and 70–80% after UVC/H2O2/Fe2+, UVC/TiO2 and UVC/H2O2/TiO2 treatments. Based on these results, UVC, UVC/H2O2 and UVC/TiO2 treatments were further investigated. UVC treatment supported the highest pollutant removal (100% in 48 h), dechlorination efficiency (81% in 48 h), and detoxification to Lepidium sativum seed germination and activated sludge respiration although irradiated samples remained toxic to Chlorella vulgaris. Biodegradation of the UVC irradiated samples removed the source of algae toxicity but this could not be clearly attributed to the removal of trans-chlordane photoproducts because the surfactant interfered with the chemical and biological assays. Evidence was found that trans-chlordane was photodegraded through photolysis causing its successive dechlorination. trans-Chlordane removal was well described by a first order kinetic model at a rate of 0.21 ± 0.01 h−1 at the 95% confidence interval.