Water Supply
System in Japan

Framework for safe drinking
water

Water & Waste Eng. 02
2024.05.26

名古屋大学減災連携研究センター

Disaster Mitigation Research Center, NAGOYA UNIVERSITY

Nagahisa HIRAYAMA

Safe Drinking Water

Disability-Adjusted Life Year (DALY)

1. INTRODUCTION

Framework
A conceptual framework for
implementing the Guidelines(Chapter 2)

Introduction(Chapter 1)

FRAMEWORK FOR SAFE DRINKING-WATER
Health-based targets(Chapter 3)

Public health context
and health outcome

Water safety plans(Chapter 4)
Systemassessment

Monitoring

Management andcommunication

Surveillance(Chapter 5)• Definition: One DALY can be the thought of as one lost year of

SUPPORTING
INFORMATION“healthy” life. The sum of these DALYs across the population,or the burden of disease, can be thought of as a measurementof the gap between current health status and an ideal healthsituation where the entire population lives to an advanced age,
free of disease and disability.

Microbial aspects(Chapters 7 and 11)
Chemical aspects(Chapters 8 and 12)
Radiologicalaspects(Chapter 9)• DAYLs for disease or health condition are calculated as the

Acceptability
aspects(Chapter 10)

sum of the Years of Life Lost (YLL) due to premature mortality
in the population and the Years Lost due to Disability (YLD) for
people living with the health condition or its consequences.

Application of the Guidelines
in specific circumstances(Chapter 6)
Climate change, Emergencies,
Rainwater harvesting, Desalination
systems, Travellers, Planes andships, etc.

Figure 1.1

Interrelationships
among the forindividual
chapters of the Guidelines©Guidelines
Drinking-water
Qualityfor-drinking4th ed., WHO,
water quality in ensuring drinking-water safety

In addition to faecally borne pathogens, other microbial hazards, such as guinea
worm (Dracunculus medinensis), toxic cyanobacteria and Legionella, may be of public

2011Calculation of DALYs• DALY = YLL + YLD• The YLL basically correspond to the number of deaths

multiplied by the standard life expectancy at the age at which
death occurs. The basic formula for YLL (without yet including
other social preferences discussed below), is the following fora given cause, age and sex:

Calculation of DALYs• Because YLL measure the incident stream of lost years of life

due to deaths, an incidence perspective has also been taken
for the calculation of YLD in the original Global Burden of
Disease Study for year 1990 and in subsequent WHO updates
for years 2000 to 2004.

• YLL = N x L• where:• N = number of deaths• L = standard life expectancy at age of death in years

Calculation of DALYs• To estimate YLD for a particular cause in a particular time

period, the number of incident cases in that period is multipliedby the average duration of the disease and a weight factor thatreflects the severity of the disease on a scale from 0 (perfect
health) to 1 (dead). The basic formula for YLD is the following(again, without applying social preferences):• YLD = I x DW x L• where:• I = number of incident cases• DW = disability weight• L = average duration of the case until remission or death

The various hazards that can be present in water can have very
different health outcomes• Some outcomes are mild (e.g. diarrhoea), wheres others can besevere (e.g. chlera, hemolytic uremic syndrome associated with
Escherichia coli O157 or cancer).

• Some are acute (e.g. diarrhoea), whereas others are delayed (e.g.
infectious hepatitis or cancer).

• Some especially relate to certain age ranges and groups (e.g.

skeletal fluorosis in older adults often arises from long-term
exposure to high levels of fluoride in childhood; infection with
hepatitis E virus has a very high mortality rate among preg- nantwomen).

• In addition, any one hazard may cause multiple eﬀects (e.g.

gastroenteritis, Gullain- Barré syndrome, reactive arthritis andmortality associated with Campylobacter).

DALY provides the common metric• In order to support public health priority setting, a common
metric is required that can be applied to all types of hazard
and takes into account diﬀerent health outcomes, including
probabilities, severities and duration of eﬀects.

• The disability-adjusted life year (DALY) provides this metric.

Basic principle of the DALY
• The basic principle of the DALY is to weight each health impact
in terms of severity within the range of 0 for good health to 1
for death.

• The weighting is then multiplied by duration of the eﬀect andthe number of people aﬀected.

• In the case of death, duration is regarded as the years lost in
relation to normal life expectancy.

• Using this approach, a mild diarrhoea with a severity weightingof 0.1 and lasting for 7 days results in a DALY of 0.002,
whereas death resulting in a loss of 30 years of life equates toa DALY of 30.

Infection with rotavirus

Infection with Cryptosporidium

in developed countries• mild diarrhoea (severity rating of 0.1) lasting 7 days in 97.5% ofcases;• severe diarrhoea (severity rating of 0.23) lasting 7 days in 2.5%of cases;• rare deaths of very young children in 0.015% of cases.
• The DALY per case can be calculated as follows:• DALY = (0.1 x 7/365 x 0.975) + (0.23 x 7/365 x 0.025) + (1 x
70 x 0.00015) = 0.0019 + 0.0001 + 0.0105 = 0.0125• Infection with Cryptosporidium can cause watery diarrhoea(severity weighting of 0.067) lasting for 7 days with extremelyrare deaths in 0.0001% of cases.

• This equates to a DALY per case of 0.0015.

Safe Drinking Water

1. INTRODUCTION

Framework
A conceptual framework for
implementing the Guidelines(Chapter 2)

Introduction(Chapter 1)

FRAMEWORK FOR SAFE DRINKING-WATER
Health-based targets(Chapter 3)

Public health context
and health outcome

Water safety plans(Chapter 4)
Systemassessment

Monitoring

Management andcommunication

Surveillance(Chapter 5)

SUPPORTING
INFORMATION

Water Supply System inJapan

Microbial aspects(Chapters 7 and 11)
Chemical aspects(Chapters 8 and 12)
Radiologicalaspects(Chapter 9)
Acceptability
aspects(Chapter 10)

Application of the Guidelines
in specific circumstances(Chapter 6)
Climate change, Emergencies,
Rainwater harvesting, Desalination
systems, Travellers, Planes andships, etc.

Figure 1.1

Interrelationships
among the forindividual
chapters of the Guidelines©Guidelines
Drinking-water
Qualityfor-drinking4th ed., WHO,
water quality in ensuring drinking-water safety

2011

In addition to faecally borne pathogens, other microbial hazards, such as guinea
worm (Dracunculus medinensis), toxic cyanobacteria and Legionella, may be of publichealth importance under specific circumstances.
Although water can be a very significant source of infectious organisms, many ofthe diseases that may be waterborne may also be transmitted by other routes, including person-to-person contact, food intake and droplets and aerosols. Depending on
the circumstances and in the absence of waterborne outbreaks, these routes may be
more important than waterborne transmission.
Microbial aspects of water quality are considered in more detail in chapter 7, withfact sheets on specific microorganisms provided in chapter 11.

History of Japan Water Supply

Development modern waterworks in Japan

Disinfection
firstmodern water supply system was introduced in• Japan’s1.1.3
Disinfection is of unquestionable importance in the supply of safe drinking-water.
Yokohama
and began its operation in 1887.
The destruction of pathogenic microorganisms is essential and very commonly involves the use of reactive chemical agents such as chlorine.

Disinfection is an effective barrier to many pathogens (especially bacteria) during
the operation in Yokohama, the water supply system• Following
drinking-water treatment and should be used for surface waters and for groundwater
to faecal contamination.
spread subject
in municipalities
allResidual
overdisinfection
Japan.is used to provide a partial safeguard against low-level contamination and growth within the distribution system.
5chlorination was imposed, was• The waterworks act, in which theimplemented in 1957.

©Japan Water Works Association, 2016

Spread in municipalities

Numbers of Waterworks in FY2014

1887 Yokohama• Large Public Water Supply: N. of customers > 5,001• Small Public Water Supply: N. of customers > 101• Private Water Supply: population exceeding 100

1889 Hakodate, Hokkaido
1891 Nagasaki
1895 Osaka
1898 Tokyo
1899 Hiroshima
1900 Kobe
1908 Yokosuka
1912 Kyoto
1914 Nagoya©Japan Water Works Association, 2016

Water Consumption
我が国における総人口の長期的推移○ 我が国の総人口は、2004年をピークに、今後100年間で100年前（明治時代後半）の水準に戻っていく。この変化は、千年単位でみても類を見ない、極めて急激な減少。

Population of Japan
Trend of Annual Water Consumption
and Maximum Daily Water Supply
出典：「国土の長期展望」中間とりまとめ 概要（平成23年２月21日国土審議会政策部会長期展望委員会）©Ministry of Internal Affairs and Communications, 2013

How much is daily average
supply per capita?

Dairy average supply per capita（L/capita・day）

Daily average supply per capita in Japan
350
300
250

318
247

261

287

322

322

307

297

200
150
100
50
0
1975 1980 1985 1990 1995 2000 2005 2010
Year

Average daily water use, a household• Japan: 200-250 L/day/capita• U.S: 80-100 gallons/day/capita 302-378 L/day/capita• U.K: 149 L/day/capita• Europe: 144 L/day/capita• China: 178 L/day/capita• India: 135 L/day/capita• Asia: 95 L/day/capita• Australia: 340 L/day/capita• Africa: 47 L/day/capita

Ministry of Land, Infrastructure, Transport and Tourism，2014

The Latest Toilet requires less than 6L

How much is the volume ofwater of one flush toilet ?

The volume of flushing water(L per flush)

20
15
10
5
0
1970

1980

1990

2000

2010

decline since World War II (Chart 1). Depopulation in Japan became inevitable after
2010 with the growing number of foreign residents leaving the country following the2011 Great East Japan Earthquake and the rising number of deaths exacerbated by thenation’s falling birth rate and aging population.
According to United Nations’ estimates, Japan’s population in 2015 ranked tenth in
the world, with 11th ranked Mexico fast catching up. Mexico with a population of 127.02
million in 2015 and a population growth rate of 7.1% in 2010-2015 is likely to overtake
Japan in 2016. Moreover, among the world’s top twenty most populated countries in
2015, only Japan registered a decline from 2010 to 2015, while populations are rising
rapidly in emerging countries ranked 12th or lower. Japan’s population in 1950 was thefifth largest in the world, but its ranking is expected to continue falling gradually in the
future.

Water in Daily LifeJapan’s Depopulating Society
Chart 1: Changes in Japan’s population and population growth(10,000)(%)

14,000(Population growth rate: right scale)

18(Population: left scale)16

12,000Other
6%Cloths washer
15%
Kitchen17%
Toilet22%
BathToiletKitchen
Cloths washer
Other

14

Uses

Amount10,000

12

8
6,000

Bath
40%

Handwash

1 minute

12 L

6
4

4,000

2
2,000

0

0

teethbrushing

30 seconds

6L

Dishwashing

5 minutes

60 L

Car washing

Keep ﬂowing

90 L

Shower3 minutes

36 L

Actual and projected population
Figure 1-1 Actual
projected population of Japan:
ofandJapan
Medium-, high-, and low-fertility (medium-mortality) projections

10

8,000

-2
(Year)

Changes in Japan’s populationand population growth

Source: Made by MHRI based on Statistics Bureau, Ministry of Internal Affairs and Communications, The Preliminary Counts ofthe 2015 Population Census (2016)

1

Tokyo Metropolitan Waterworks Bureau©National Institute of Populationand Social Security Research, 2017
Figure 1-2 Trends in the proportion of elderly (aged 65 and over):Medium-, high-, and low-fertility (medium-mortality) projections％

Projected Population of Aichi Prefecture
2045年
2040年
2035年
2030年
2025年
2020年
2010年
2050年

Water supply system
Water resource
Treatment
IntakeTransmission
Water service
Raw water
Dam
Distribution
Reservoirtransmission
River

Intakemain

Distribution pipe
Transmission
main
23
Purification
plant

Groundwater©National Land Numerical Information, 2018

Well

Sedimentation tank
Sand Filtration
Ozone + GAC
UVDisinfection

servicereservoir

TapreceivingtankNabeya Ueno Water Purification Plant, Nagoya City

Basic Water Purification Process
Annual fresh water Volume:
14.93 billion cubic meter
Membran Filtration• Removal of turbidity & disinfection
2.4 (1.6%)• ProcessSlow Sand Filtration(3.2%) 4.8• Slow sand filtration
Chlorination Only
25.3 (17.0%)• Rapid sand filtration• Membran filtration
Rapid Sand Filtration• Chlorination only
116.8 (78.2%)• Advanced water treatment (ozone+GAC(Granular activatedcarbon))Slow Sand Filtration

Slow Sand Filtration

OutlineAdvantages(1)• Slow sand filtration is an efficient method of removing particulate• Quality of treated water• No other single process can effect such an improvementin the physical, chemical, and bacteriological quality ofnormal surface waters as that accomplished by biologicalfiltration. No chemicals area added, thus obviating one
cause of taste and odour problems.
• Cost and ease of construction• The simple design of slow sand filters makes it easy touse local materials and skills in their construction.

suspended matter and is therefore applicable to the treatment ofgroundwater containing solids in suspensions.

• Its principal use is in the removal of organic matter and pathogenicorganisms.

©WHO, 2006

Slow Sand Filters

Slow Sand Filters

Advantages(2)Limitations(1)• Cost and ease of operation• No imported chemicals or other materials are needed forthe process, though in many cases chlorination ispracticed as an additional safeguard.
• Conservation of water• Not requiring the regular flushing to waste of wash water• Disposal of sludge• The waste material is usually accepted by farmers as a
useful dressing for their land.

• Where land is restricted or very expensive, the much larger area

Slow Sand Filters

Slow Sand Filters

Limitations(2)Limitations(3)• Where unskilled labour for cleaning is in short supply it may be easier• Where the water to be treated is liable to severe and sudden changes in• In climates where the winters are very cold it may be necessary to install• Certain types of algae may interfere with the working of the filters, theand cheaper to recruit the skilled staff required to operate and maintainrapid filters. However, the mechanical cleaning of slow sand filters has
been developed.
expensive structural precautions against freezing.

needed for biological filters. The areas required for treatment plants vary
widely.

• In countries where construction methods are largely mechanized andwhere the importation of such materials as steel and cast-iron pipeworkpresents no problems, the reinforced concrete construction and metal
fittings of rapid filters may be cheaper to construct then the more
extensive non-reinforced construction of slow filters.

quality or where certain types of toxic industrial wastes or heavy
concentrations of colloids may be present, the working of biologicalfilters can be upset.

usual result being premature choking, which calls for frequent cleaning.
In such cases it may be necessary to cover the filter-beds to exclude lightA Typical Rapid Sand Filter

Rapid Sand Filtration
Pre-Treatment

CoagulationFlocculation

Post-Treatment

Rapid Sand
Filtration

Chlorination• Rapid sand filters use relatively coarse sand and other granular media toremove particles and impurities that have been trapped in a floc throughthe use of flocculation chemicals—typically alum (aluminum sulfate
Al2(SO4)318H2O, Polyaluminum chloride(PAC) (Al2(OH)nCl6-n)m ).

©Sustainable Sanitation and Water Management, www.sswm.info, 2016

Design and operation

Advantages of RSF• Mixing, flocculation and sedimentation processes are typical treatment• Much higher flow rate than a slow sand filter• Requires relatively small land area
• Less sensitive to changes in raw water quality, e.g. turbidity• Requires less quantity of sandstages that precede filtration.

• The two types of rapid sand filter are the gravity type and pressure type.
• A disinfection system (typically using chlorine or ozone) is commonlyused following filtration.

• Rapid sand filters must be cleaned frequently, often several times a day,by backwashing, which involves reversing the direction of the water andadding compressed air.

Disadvantages of RSF

Questionnaire Survey• Large pore size will not, without coagulant or flocculent, remove• Internet-based, residents in Japan• Duration: 2 days (March 21 - 22, 2012)• 1,000 responses (male: 50%, female: 50%)

pathogens smaller than 20 micro-meter like Cryptosporidium.

Male

Female200

N. of response (person)

N. of response (person)• Requires greater maintenance than a slow sand filters.
• Generally ineffective against taste and odor problems.
• Produces large volumes of sludge for disposal.
• Requires ongoing investment in costly flocculation reagents.
• Treatment of raw water with chemicals is essential.
• Skilled supervision is essential.
• Cost of maintenance is higher.

150
100
50
0

hu
us
Ky u
k
iko
Sh ku
o
ug
Ch i
nk
Ki
u
ub
Ch
o
nt
Ka
u

ok

do

ai

• Ozone• Removal of offensive taste and odor
• Reduction of THMs formation potential• Activated Carbon• a form of carbon processed to have small, low-volume pores that

20

OthersBottled waterWith purification
systemBoiled water10
Tap water

Response (%)

0Female

30

0

50

kk

Male

40

100

Advanced Treatment Process (Ozone+GAC/BAC)

Alternative Drinking Tap Water
50

150

h
To

Age

Female200

Ho

10 20 30 40 50 60 70 80

Male

250

©N. Hirayama & S. Itoh, 2015

increase the surface area available for adsorption or chemical reactions• Removal of offensive taste and odor, organic carbon matter, synthetic
detergent, pesticide• PAC (Powdered Activated Carbon)• GAC (Granular Activated Carbon)• BAC (Biological Activated Carbon)

Advanced Treatment Process (Ozone+GAC/BAC)
Raw
water

Coagulation
Flocculation

Pre-chlorination

RSF

Ozonation

Intermediate
chlorination

Coagulation
Flocculation

Ozonation

Raw
water

Coagulation
Flocculation

Pre RSF

Ozonation

BAC Filter

BAC Filter

Cost of construction △Treated water Quality ◎

Tap
water

RSF

Raw
water

Coagulation
Flocculation

Post
Ozonation

Cost of construction △

RSF

Pre
Ozonation

Treated water quality ◎Cost of construction △Cost of operation ○Membrane Filtration Process• Membranes are commonly used at various stages in the water• MF: Micro-filtration• 0.01 - 10 micrometer• UF: Ultra-filtration• Molecular weight 1,000 - 3 million• NF: Nano-filtration• Molecular weight 100 - 1,000• RO: Reverse Osmosis• Molecular weight - 350• In general, membrane processes oﬀer the possibility ofseparating water from various types of solute and of separating
solutes either on the basis of size or because some are ionizedand others are not.

• In addition to these cases where a high degree of separation isachieved, there are many instances where the composition of the
dissolved material is altered.

BAC Filter

Tap
water

Post-chlorination

Membrane Process
treatment process.

Tap
water

Cost of operation ○Post-chlorination

Cost of operation ○Post RSF

Intermediate Post-chlorination
chlorination

Cost of operation △Intermediate
chlorination
Treated water quality ◎

Tap
water

Post-chlorination

Treated water quality ◎ Cost of construction △

Raw
water

GAC Filter

Advanced Treatment Process (Ozone+GAC/BAC)Separating Water from Various Types of Materials

Kawai Water Purification Plant (Yokohama City)

Molecular
weight
RO
NF

PAC,
GAC,
BAC

102

Dissolved
solids103

1Å Ammonium nitrogen, Calcium,
Chloroform, Trichloroethylene,
Geosmin, Residual agricultural chemicals
1nm

104

UF

10nm

105
106

Fulvic acis
Humic acid
Virus

Colloid
0.1μm
Clay

MF

Coagulation
Flocculation

Suspended
solids1μm

Bacteria

Capacity: 172,800 cubic meter per day

Silt, Algal fungiGold Coast Desalination Plant, Queensland, Australia

Water Quality Standards of Drinking Water©Japan Water Works Association, 2016

Future Water Supply Services in Japan

Principles of New Waterworks Vision

New Waterworks Vision• In June 2004, the Ministry of Health, Labour and Welfare had

issued the “Waterworks Vision” and indicated the desire state ofwaterworks in Japan in the future together with the policies andpathway towards realization of such a vision. More than eight years
have passed since release of the Vision, and the circumstances
surrounding waterworks in Japan have changed significantly.
• In response to such changes, the Ministry radically reviewed theWaterworks Vision and formulated and announced the New Vision
for the next 50 years and a century ahead. From FY2013, all theparties concerned will advance various steps toward realization of
the ideal waterworks by sharing the principles of the “New
Waterworks Vision” based on the aspects of “safety”,“resilience”, and “sustainability”.
©Japan Water Works Association, 2016

Safety, Resilience, and Sustainability

Partial Revision of the Waterworks Act, 2018

• Safety• Waterworks provides tasty drinking water to all the people at• The objectives of partial revision of the Waterworks Act are to reinforce

any time and any place.

• Resilience• Waterworks minimize suﬀering from natural disasters etc. andare flexibly and quickly recoverable from the damage whensuﬀered.

• Sustainability• Waterworks ensure a sound, stable water supply despite

diminishing population to receive the supply of water anddecreasing supply of water.
©Japan Water Works Association, 2016

the waterworks management bases, and to respond the subjects whichwaterworks in Japan are faced with, for example decreasing water
demand due to depopulation, deterioration of water supply facilities, acritical shortage of human resources.
1. Clarification of the accountability of the person concerned
2. Promotion of the wide area cooperation
3. Promotion of appropriate asset management
4. Promotion of the public-private partnership
5. Improvement of system for designated water pipe plumberPublic-Private Partnership• Private Finance Initiative (PFI)• Concession Agreement• In the case of a public service concession, a private company enters

into an agreement with the waterworks to have the exclusive right tooperate, maintain and carry out investment in a public utility for a given
number of years. Other forms of contracts between public and private
entities, namely lease contract and management contract (in the watersector often called by the French term aﬀermage), are closely related
but diﬀer from a concession in the rights of the operator and its
remuneration. A lease gives a company the right to operate andmaintain a public utility, but investment remains the responsibility ofthe public. Under a management contract the operator will collect therevenue only on behalf of the government and will in turn be paid anagreed fee.

One more thing…

Water Supply Cost and Water Charge in Japan

Discussion• Water Supply Cost

Imagine;• Domestic usage of 20 cubic meter/month: 3,254 JPY• Water Charge• Domestic usage of 20 cubic meter/month: 3,226 JPY

You are a resident of the A city.
The mayor of A city declare that a private enterprise will manage thewater utility of the A city.
Do you agree?

A. YES
B. NO