It’s no surprise that Tokyo offers high-quality water that is easily accessible from every tap in the city. Japan is renowned for its commitment to cleanliness and advanced technology, and they have leveraged these values to ensure that their capital city’s drinking water is treated to the highest standards.

Numerous individuals opt to purchase bottled water instead of consuming tap water. However, the truth is that many drinking water facilities produce water that is equivalent to, if not superior to, bottled water. Tokyo is a prime example of this.

The Ministry of Health, Labor, and Welfare has established 51 rigorous quality standards to safeguard the fundamental quality of drinking water in Tokyo. These standards incorporate tests for toxicity and hazardous pollutants, as well as assessments to guarantee desirable attributes such as color, clarity, and odor. Public water supplies in Japan are subject to more stringent regulations than those governing bottled spring water. Additionally, Tokyo’s water surpasses these standards due to the metropolitan waterworks’ stringent treatment procedure that examines approximately 200 safety and quality parameters.

Tokyo’s water supply is managed by five treatment plants under the Tokyo Waterworks. Misono Water Purification Plant, one of the five, has the capacity to treat 300,000 cubic meters (roughly 80 MGD) of water daily using conventional treatment, as well as ozone and biological activated carbon. This supplementary step effectively eliminates almost all remaining impurities from the water.

As a potent oxidizing agent, ozone reacts with a broad range of pollutants, including cancer-causing substances and microorganisms like bacteria and protozoa. This process eliminates any potential health hazards and enhances the water’s taste and odor.

During the second phase of the process, water travels from the ozone contact chamber to biofiltration ponds that contain various grades of biological activated carbon. This microporous carbon not only eliminates organic impurities similarly to a home water purifier, but it also promotes microorganisms that decompose remaining impurities and byproducts of ozone treatment. If left untreated, these pollutants can diminish the water’s taste and aroma.

The degree of water treatment depends on the quality of the source water. Currently, Tokyo derives 80% of its water from the Tonegawa and Arakawa Rivers, while the remaining 20% is obtained from the Tamagawa River. The Tamagawa River’s purity is such that standard treatment suffices to make it safe for drinking. However, the Tonegawa and Arakawa Rivers necessitate the advanced treatment methods described earlier.

Numerous large-scale drinking water facilities in the US and Canada have adopted the ozone biofiltration treatment method. As a matter of fact, more than 1.6 billion gallons of water are treated with ozone each day in the US alone. Several of these facilities have conducted blind taste tests, pitting tap water against bottled water to determine which is superior, and in numerous cities that employ advanced ozone water treatment, tap water has emerged victorious.