The Use of Weakly Acidic Spent Bathwater Mixed with Electrolyzed Water for Laundry

This study was conducted to develop a method for reusing of spent bathwater in Japan which was disinfected by weakly acidic electrolytic treatment. Electrolyzed water obtained from electrolytic treatment without a diaphragm (single cell) was diluted with spent bathwater and used to launder fabrics. The spent bathwater did not remove dirt from the fabrics well, but it effectively sterilized the washed fabrics. The detergent efficiency was found to decrease by about 5% when spent bathwater was used when compared to non-treated spent bathwater. The decreased detergent efficiency was believed to be caused by reduced foaming and affinity. To obtain a sufficient sterilization effect without decreasing detergent efficiency, untreated spent bathwater was used for washing, after which spent bathwater mixed with electrolyzed water was used for rinsing. Even when rinse times as short as one cycle for 3 min were used, this method led to sufficient sterilization of fabrics for laundry. Additionally, odor testing using an odor concentration meter and evaluation by a monitor panel showed that electrolytic treatment markedly decreased the odor level of the test fabrics. Overall, these findings indicated that bacteria on fabrics could be effectively attenuated with no decrease in detergent efficiency if electrolyzed water diluted with spent bathwater was used for rinsing after washing with untreated spent bathwater.