Abstract
A tap water derived electrolyzed water that is remarked by specifically-elevated available chlorine concentration (ACC: <5mg/L) is examined for the stability of its properties during preservation under closed as well as open conditions. Under the closed condition, ACC decreased slowly at a constant rate regardless of its initial concentration. The initial ACC of 1 and 2mg/L decreased to the tap water level (0.2mg/L) after 1.5 and 4 months, respectively. In case of the initial ACC of 4.5mg/L, however, it remained at 1mg/L even after 8 months in spite of the decrease of half of the initial ACC after 3 months. The water qualities of electrolyzed waters of which ACC returned to the tap water level was within the range of Japanese water quality standards as well as WHO guideline. Under the open condition, about 2mg/L of initial ACC decreased to the tap water level in about 90min. in case of a small amount (about 15mL in a petri dish) of the electrolyzed water, whereas 24hr was needed for a large amount (800mL with stirring in a 1L vol. beaker) of the electrolyzed water. The resulting water showed quality in the range of Japanese tap water quality as well as WHO drinking water guideline.
Concerning the electrolyzer (electrode) durability, continuous repeated use resulted in a steady decrease in electro-currency and ACC productivity. The electro-currency of 0.38A and ACC productivity of 1.5mg/L at the beginning decreased to 0.2A and 0.8mg/L after 450hr continuous use and to 0.03A and 0.3mg/L after 600hr continuous use, indicating the lifespan of the electrode. The water passed through the 600hr continuously used electrode showed the water quality equivalent to that of Japanese tap water.
