2000 Volume 48 Issue 3 Pages 559-564
Among several electrolyzed NaCI solutions, there are three types such as strong acid (<pH 2.7), weak acid (pH 5-7), and weak alkaline (pH 7-9), which have strong bactericidal activities. We examined physicalchemical and preservative properties of the three type solutions and compared each other to seek for possible candidates for application in aquaculture fields. All solutions were prepared with an electrolyzed water generator without a diaphragm. Characteristics of the solutions just after preparation are: strong acidic type (pH: 2.4, oxidation-reduction potential: +1170 mV, residual chlorine: 15.0 mg/l), weak acidic type (5.6, +995 mV, 12.5 mg/l), and weak alkaline type (8.2, +730 mV, 17.0 mg/l). In preservative test, the solutions in stoppered bottles were kept in a dark room at 20°C and 5°C, respectively. The bactericidal activities were measured by a commercial test paper for living bacteria. As time passed, the bactericidal activities of the all three types dropped remarkably at both 20°C and 5°C, corresponding to decrease in residual chlorine. However, the activity decline was slower in the alkaline type than in other types. From our results, we concluded that the weak alkaline solution is suitable for application in aquaculture fields.
