It has been well documented that potassium ferrate is a strong and environmental friendly oxidant. Under the acidic conditions, the redox potential of ferrate (IV) ions is higher than that of molecular ozone. The product of the ferrate (IV) oxidation reactions is considered to be the ferric hydroxide, which is a useful coagulant and can enhance the water remediation performance. Additionally, others disinfectant chemicals including chlorine and ozone, which are powerful and successful to combat the harmful micro-organism-causing problems, but such disinfectants have been confirmed to be of health concern. So, as a healthy potential alternative, potassium ferrate has been widely used in the fields of drinking water and wastewater treatmenti; however, there is no available report of its application to aquaculture. The purpose of this study is to investigate whether potassium ferrate can be used as an aquacultural disinfectant. Prior to this study, the concentration of potassium ferrate was determined by spectrophotometry. The equation of concentrations of Fe2+ against OD values was obtained: OD = 0.005 + 12241.071 C-Fe(2+) (r =0.9985), and then through transformation, the purity of potassium ferrate was 29.75%. In this study, eight kinds of fish-pathogenic bacteria were selected (Aeromonas sobria, Yersinia ruckeri, Aeromonas hydrophila, Vibrio flurialis, Aeromonas punctata subsp. Punctata, Pseudomonas fluorescent, Vibrio group I freshwater subgroup, Aeromonas punctata f. intedtinalis), the MIC (minimal inhibitory concentration, MIC) and MBC(minimal bactericidal concentration, MBC) of potassium ferrate against them were obtained, and the effect of potassium ferrate solution in different concentrations to sterilize these test germs were mensurated. The results showed that potassium ferrate had a better effect on inhibiting Aeromonas sobria, Vibrio flurialis, and Vibrio group I freshwater subgroup, and their MIC values were 1.2 mg/L. At the same time, the MBC values of these eight kinds of fish-pathogenic bacteria were obtained, they were 9.6 mg/L, 19.2 mg/L,9.6 mg/L, 9.6 mg/L,19.2 mg/L, 19.2 mg/L,9.6 mg/L, >19.2 mg/L, respectively. When the test pathogens density was regulated approximately to 10(5) cfu/mL, the germicidal efficacy of potassium ferrate solution in different concentrations against the pathogens was determined after an hour. Exhilaratingly, the vibrio were sterilized completely by potassium ferrates solution in lower concentrations than others. When the concentration of potassium ferrate solution were adjusted to 2.4 mg/L and 7.2 mg/L, their bactericidal coefficients were 94.21%, 100% and 95.45%, 100%, respectively. Based on the above results, the growth trends of these two kinds of vibrio were constructed. The figure showed that with higher concentration of potassium ferrate solution, the quantity of Vibrio flurialis and Vibrio group 1 freshwater subgroup were larger. It was clear that potassium ferrate could be used as an aquatic disinfectant for both bath treatment of fish and splash treatment of the whole pond, as well as potassium ferrate can be used to prevent the fish vibriosis. However, the mechanism of potassium ferrate sterilizing germs remains unknown, and need to make further investigation.
Liu Qian-Fu (email@example.com) ; Wang Jian-Guo (firstname.lastname@example.org) ; Li Ming; Ling Fei; Gong Xiao-Ning.THE GERMICIDAL EFFICACY OF POTASSIUM FERRATE (K2FeO4) AGAINST SEVERAL FISH-PATHOGENIC BACTERIA,Acta Hydrobiologica Sinica,2009,33(5):818-825