EVALUATION OF FRESH HERBAL BATH WATER ON GROWTH OF IRON BIOFILMS ON TUB SURFACE

The Geriatric Health Service Facility at Wasanosato, Kawabe, Wakayama, provides fresh herbal bath for clients. The care worker observed an apparent reduction in iron biofilms produced by iron bacteria on the tile surfaces of hot bath water tubs since fresh herbs were steeped into the bath water. In this study, iron biofilms in hot bath water were evaluated after using five kinds of herbs, Lemonbalm (Melissa officinalis), Applemint (Mentha suaveolens), Coolmint (Mentha arvensis var. agrestis), Rosemary (Rosmarinus officinalis), and Lavender (Lavandula angustifolia), for 8 days to observe the color and environmental water conditions. The pH, oxidation and reduction potential (ORP), dissolved oxygen (DO), and electrical conductivity (EC) of the bath water were measured in laboratory periodically. The filtered water and scale samples were air-dried up at room temperature, 10°C and 500°C heating treatments for the evaluation of organic and inorganic compositions. The powder samples were mounted on Mylar film. The chemical analysis was carried out by an energy dispersive X-ray fluorescence spectrometer (ED-XRF, JEOL JSX-3201). The results indicated that the pH of five kinds of herbs were constant at the range of pH 6.8－7.0, for 8 days under reducing conditions (ORP ranges from - 226 to 75 mV; DO ranges from 0.8 to 2.1 mg/L). During the experiment, the herbs were dissolved to produce ions of Mg, P, and K, indicating high EC values from 1.38 to 1.99 mS/cm. This suggests that the herbs have restraining influence on the iron biofilm in hot bath water, in association with the composition of chemical elements and EC values. For comparison, the bath water without herbs indicated pH 8.4, ORP 90 mV, DO 8.9 mg/L, and EC 0.42 mS/cm, showing no Mg, P, and K compositions. The herbs containing a large amount of Mg, P, and K may remove iron biofilms and contribute to better water condition.