TOC Analysis of Hot Spring Water and Bathtub Water

Introduction

In Japan, water quality standards and inspection methods are provided for inlet hot water (unrecycled hot water supplied directly to the bath), original water (water used for hot water and temperature adjustment), and bathtub water used in public bathhouses. Until recently, the organic content of these types of water had been evaluated by potassium permanganate consumption, but under a recent revision of Guidelines for Management of Sanitation, Etc. in Public Bathhouses, evaluation by total organic carbon (TOC) was added (as of Sept. 19, 2019, Ministry of Health, Labour and Welfare Notification EF 0919, No. 8 of the Director-General of the Department of Environmental Health and Food Safety). As a result of this revision, it is now possible to measure the organic content by either TOC or potassium permanganate consumption. The potassium permanganate consumption test requires much manual work, including preparation of the reagent, boiling, and titration, which occupy the analyst’s time. In contrast, TOC is an instrumental analysis technique, and stable results can be obtained regardless of the analyst. If a sampler is used, continuous analysis of multiple samples is also possible, and the work efficiency of the laboratory can be improved by running the sampler at night. Moreover, when hot spring water (geothermal water) is used in inlet hot water or bathtub water, the water sometimes contain chlorides, sulfates, and alkali salts originating from the hot spring. Although the measured values obtained in the potassium permanganate consumption test may be affected in some cases if the sample contains oxidizable substances other than organic compounds, TOC measurements are not affected by coexistent substances. This article introduces an example of evaluation of the organic content in hot spring water used as bathhouse water and water containing bath additives using a Shimadzu combustion-type TOC analyzer.

January 21, 2020 GMT