Measures to Provide Good-Tasting Tap Water in JapanJWRC Study Group for International
Comparison of Water Supply Services

August 2018

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What is Good-Tasting Drinking Water?
Japan’s Ministry of Health and Labour
published the guideline values for goodtasting drinking water in 1985. The
publication was a response to an increasing
demand for better tasting-tap water among
the general public, which was prompted byan intensified advertisement of bottled waterby various manufacturers.

Guideline values for good-tasting drinking
water set by Japan’s Ministry of Healthand Labour in 1985
ItemValue

Total residue

30-200mg/L

Hardness

10-100mg/L

Free carbonate
Potassium permanganate
consumption
Odor index

3-30mg/L

Residual chlorine≤0.4mg/L

Temperature≤20℃≤3mg/L<3Source: The Research Group on Good-Tasting Drinking Water.
1985. “About Good-Tasting Drinking Water.” The Journal of
the Japan Water Works Association. Vol. 54 (5).

3Measures being taken by Japanese water utilities toensure good-tasting tap water
1. Technical Approaches

2. Communicative Approaches

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1. Technical Approaches

1.1 Water Quality Targets on Good-Tasting Water
Method: Set more stringent local water quality targets than the national standards
ItemUnit

National water
quality standards

Utility’s water
quality target

Target attainment(FY2016)

Residual chlorine

mg/L

0.1-1.00.1-0.4

86.2 %

Trichloramine

mg/L

-

0100 %

Threshold odor
number (TON)

-

≤3

1

100 %

2-MIB

ng/L

≤100100 %Geosminng/L≤100100 %Total organic
compounds (TOC)

mg/L

≤3

≤1100 %Color

Color unit

≤5≤1100 %

Turbidity

Japanese unit*

≤2

≤0.1

100 %

Source: Tokyo Metropolitan Waterworks Bureau*The Japanese turbidity unit is based on polystyrene latex suspension. Depending on the turbidity characteristics,
1 degree is equivalent to 0.7–0.9 NTU (Nephelometric Turbidity Unit).

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1.2 Odor Control
Method: Advanced water treatment
Certain combinations of water treatment processes are called an “advanced watertreatment” in Japan (e.g. traditional rapid filtration combined with ozonation andbiological activated carbon absorption).
The advanced water treatment process can remove various substances that a traditional
treatment cannot, reducing musty odor and chlorine smells in the tap water.
Ozone contact basin

Ozone generator

Source: Tokyo Metropolitan Waterworks
BureauSource: Chiba Prefectural Waterworks
BureauOzone contact basin

71.3 Reduction of Residual Chlorine
Method: Automatic water quality monitors
The 24/7 monitoring of residual chlorine at the distribution reservoirs and the customer
tap contributes to a systematic water quality management.
Residual chlorine at thecustomer tap (average)

Automatic water quality monitors at
131 locations in Tokyo

Automatic water quality monitors

残留塩素濃度Residualchlorine (mg/L)（mg/L）
1.00
0.90

0.80
0.70

0.83 0.82

0.78 0.76
0.68
0.60 0.59

0.60

0.56 0.56 0.57

0.500.400.30
2006 2007 2008 2009 2010 2011 2012 2013 2014 2015year
年度

Source: Chiba Prefectural Waterworks
BureauSource: Tokyo Metropolitan Waterworks Bureau
Source: Public Enterprises Agency,
Kanagawa Prefectural Government

1.4 Re-Chlorination to Keep Proper Residual Chlorine Concentration
Method: Additional chlorine feeder
Japan’s Waterworks Act requires a certain amount of residual chlorine to be maintained at the point ofcustomer tap. But dosing much chlorine at the water treatment plant (WTP) so that households far from theplant could meet this requirement might adversely affect the taste of tap water at the households closer tothe plant. The chlorine feeder installed in the distribution network would allow plant operators to containthe chlorine dose at the plant, hence better tasting tap water even at the plant’s nearby households.

Inflow

Normaldose

Additional chlorine feeder

Multi-point chlorine doseSingle-point chlorine dose

Low dose

Inflow

WTP

WTP
Reservoir

Normaldose

Reservoir

Slightlylow doseHighconcentration

Chlorine
feed point

Slightly highconcentration
Optimalconcentration

Optimalconcentration

Source: Chiba
PrefecturalWaterworks
BureauSource: PublicEnterprises Agency,
Kanagawa
PrefecturalGovernment

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2. Communicative Approaches

102.1 Educational Talk Events
Method: Utility staff talk about how goodtasting tap water is produced at local
elementary schools to educate children.

Utility staff speaking at an outreach lecture

Source: Chiba Prefectural Waterworks Bureau112.2 Public Water Tasting Events
Method: Promote the use of tap water by hosting water tasting events where
local residents can compare the taste of bottled water and tap water.
At a public water tasting event

About half of the participants said “tap water tastedbetter.” (of all the 17,6000 participants at various water
tasting events hosted in Tokyo since 2012)

BottledWater
50% ofParticipants

Source: Chiba Prefectural Waterworks Bureau

TapWater
50% ofParticipants

Source: Tokyo Metropolitan Waterworks Bureau122.3 Special Meetings to Improve Tap Water Quality
Method: hosted special meetings to improve tap water quality
with participation from the general public and academics.
Reviewed and reflected their opinions and suggestions andenhanced customer satisfaction over the past ten years.
Meeting to improve tap water quality

Customersatisfaction fortap water
increased from
30% to 78%
over ten years
Unsatisfied

29.6%
Satisfied

FY2006

55.6%
Satisfied

FY201077.8%
SatisfiedSatisfied
Neither satisfied
nor unsatisfied

FY2015

Source: Chiba Prefectural
Waterworks Bureau

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