Feasibility study on ecotoxicity of marine ecosystem against total resdiual oxidant resided after water quarantined with ozonation

초록

In this study, the ecotoxicity effects of total residual oxidants (TRO) released after ozone treatment in seawater on marine ecosystmes, and their synergistic toxic potential with existing marine environment was investigated, while the presence of microplastics during ozonation was assessed through three species of marine bacterial and Vibrio fisheri bioassay. To evaluate the behavior of TROs, ozone (0.2, 0.5, 0.7, 1.0 mg O3/min) was injected into 1 L of artificial seawater (PSU = 35, pH = 8.20) for 1 hour. The produced TRO (< 0.1 mg/L) was remained for up to 9 days and its concentration was determined by colorimetric N,N-Diethyl-p-phenylene diamine (DPD) reagent method. Edwardsiella tarda, Streptococcus mitis and Vibrio harveyi (7.1 X 10^6 CFU/mL) were used as an indicator species, which were removed when 3 mg, 5 mg, and 4 mg of O3/min were injected for 10 minutes respectively, giving > 99.8% removal. Furthermore, toxicity was evaluated after injecting 100-500 um size of PE, PS, and PET by weight (0.05 g, 0.25 g, and 0.5 g respectively) under the same conditions. The ecotoxicity analysis was performed by colony conunt. ATP assay and Vibrio fisheri bioassay. Significant difference wasn`t found in the toxicity analysis from microplastics as compared to control sample (Vibrio fisheri inhibition rate = 60%). The physical characteristics of microplastics were observed through SEM and FT-IR analysis which showed no difference from those of virgin plastics. However, it has been confirmed that toxicity was totally removed by the introduction of 50 mM of Na2S2O3.