Clarifying the characteristics of Japan's water environment from the quality of tap water in Japan

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K15121
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 22060:Environmental systems for civil engineering-related
• Research Institution: The University of Tokyo
• Principal Investigator: Hori Mayumi 東京大学, 教養学部, 特任助教 (50782869)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 水道水 / 水質調査 / 硬度 / 日本国内分布

Outline of Final Research Achievements

We conducted a comprehensive overall tap water hardness assessment for Japan. Tap water was collected from 990 points throughout Japan, and its standing position was quantitatively clarified by prefecture. Compared with 28 countries, tap water in Japan exhibited low-mineral content and presented as soft water. Japanese tap water hardness was 50.9 mg/L and that was classified as soft water, but its distribution was large throughout the country. The change of tap water hardness in the Japanese supply system and revealed that the hardness variation range can change 20% during water purification processes and in the tap water-supply systems. A comparison of the variations in hardness showed that there was no daily fluctuation in hardness and it was generally stable. In Japan, the hardness of tap water was not affected by piping but by the quality of the raw water.

Free Research Field

環境分析化学

Academic Significance and Societal Importance of the Research Achievements

日本の水道水について全国レベルの網羅的分析はこれまで例がなく、本研究による水道水の性質を特徴づけた大規模調査のデータは、基礎的データとしてさまざまな分野で広く活用される有用な知見となり、大きな学術的意義があると考えられる。また、水道水の最大消費者である一般市民にとっても有用なデータとなり得ることから、社会的インパクトは大きいものと考えられる。