抄録
Chlorination of secondary effluents produce strong toxic substance such as monochloramine or oxidant on growth of aquatic organisms. Therefore, alternative disinfection methods to chlorination should be considered. However, the effect of effluents disinfected with the alternatives on seaweed has not been clarified. In this study, the toxicity of secondary effluents disinfected with chlorine (NaOCl), chlorine dioxide (ClO2), ozone (O3), and ultraviolet rays (UV) were investigated by bioassay using Porphyra yezoensis conchospores. Secondary effluents used in this study were disinfected with disinfectants or rays which inactivated coliform groups in secondary effluents of 99.9%. Lowest-observed-effect concentrations (LOECs) of secondary effluents disinfected with NaOCl, ClO2, and O3 for germination ratio of conchospores were 1.0, 10, and 100% of effluent concentration, respectively. The toxicity of effluents disinfected with NaOCl and ClO2 were very strong. In contrast, the effluents disinfected with UV rays did not affect the germination of conchospores. The toxicity of effluents disinfected with NaOCl, ClO2, and O3 were considered to depend on initial total residual oxidant (TRO). Dechlorination with Na2SO3 of effluents disinfected with NaOCl or ClO2 did not affect the germination of conchospores, even in 100% of effluent concentration.
