Case

Water Quality Management

Water utility

Bureau of Waterworks Tokyo Metropolitan Government

General information of the utility (as of October 1, 2018 unless otherwise specified)
OperationtypePublicService area (km2)

1,239Population
served13.50 million

Distribution(m3/d)

421

Servicecoverage
(%)

100.0

Pipe length (km)27,195NRW (%)

3.25 (water loss)1

Number of staff

3,7472

Number ofwater
sources

Surface water (5), Groundwater (279), Others (Subsoil water x 8)*2

Water rates(JPY)

2077.23(in case of 10m3 of water use per month forresidential customers)

Water supply service is an important lifeline that supports our daily lives
and urban activities. The quality of tap water is required to meet the drinking
water quality standards based on the Waterworks Act, and the Bureau ofSummary

Waterworks Tokyo Metropolitan Government is making every effort for water
quality management to maintain a stable supply of safe, refreshing, highquality tap water. This paper presents the water quality management at theBureau, which supplies water to approximately 13.5 million people in the 23wards and 26 cities and towns in the Tama area, and how the utility addresses
emerging water quality issues.
1. Water quality inspection system
The Waterworks Act stipulates 51 parameters for drinking water quality
standards, 26 parameters for water quality management targets, and 47

Current Status& Challenges

parameters for which further consideration is required, as well as theparameters for daily inspections. At the Bureau of Waterworks Tokyo
Metropolitan Government (Bureau), the Water Quality Center is playing acentral role in improving the utility’s water quality inspection capabilities interms of both technology and equipment, and is responsible for ensuring anappropriate inspection system is in place.

1 water loss (%) is listed instead of NRW
2 as of August 1, 2020
3 budget for FY2019; calculated from the unit selling price for 1m3 for a month(1) Acquisition of the international standard certification
The Bureau has obtained accreditation for its water quality inspections
under an international standard (ISO/IEC17025), which objectively guarantees
a reliability of inspection results, and has been implementing water quality
inspections on its own. The Water Quality Center obtained certification for
metals in March 2004, and later for volatile organic compounds in March
2007. The Water Quality Testing Laboratory at the Tama Water Supply Reform
Promotion Division also obtained certification for metals and volatile organic
compounds in March 2007.
(2) Water quality inspection plan
In the utility’s "Water Quality Inspection Plan for FY2019" published inMarch 2019, test points were set at 131 locations in Tokyo where automaticwater quality meters had been installed, as well as at the entrance and exit ofwater treatment plants (stations). The plan also determined an appropriate
inspection frequency depending on the characteristics of the water quality ofdifferent water sources. The inspection plan and inspection results have been
published on the utility’s website.
2. Water quality management from source to tap(1) Water quality management of water sources
The main water source of the Bureau is surface water, which is derived fromalmost the entire Kanto region, including the Tone River, Arakawa River,
Edogawa River, Tama River, and Sagami River. Subsoil water and groundwater
are also used as a water source, mainly in the Tama area. To understand thewater quality of such a wide range of water sources, and to use that
information for water quality management in reservoirs and for proper water
treatment, and for water quality conservation of the water sources, as well as
for an early detection of water quality anomalies and prompt and appropriate
response in case of pollution incidents, the following measures are being
implemented.
••

Periodic water quality inspections at about 70 survey points
Patrol monitoring of water quality via water testing vehicles, etc.

•Establishment of an emergency contact network and coordination in caseof water quality incidents as well as the investigation on the incidents•

Proper management of water source forests and concluding agreementswith upstream areas of the Ogouchi reservoir and with surrounding
towns and villages•

Collecting information on the water discharged from factories and otherconstructions in the water source catchment area and requesting
2/7

cooperation for pollution prevention(2) Water quality management at water treatment plants (stations)
At the water treatment plants (stations), water is treated by rapid filtration(coagulation, sedimentation and sand filtration), slow filtration, andmembrane filtration processes. In addition to rapid filtration, the treatment
plants use, depending on the water quality conditions, powdered activatedcarbon and advanced water treatment process that combines ozonation andbiological activated carbon process. Also, since October 2013, all the water
abstracted from the Tone River system has undergone advanced watertreatment.
In order to further improve water quality management, the Bureau
formulated the "TOKYO Advanced Quality Program (Tokyo Metropolitan
Government's Water Safety Plan)" for its water treatment plants and started
implementing it in 2008. This program aims to achieve a higher level of water
quality management by integrating the following three components: the risk
management based on the Water Safety Plan proposed by the World HealthOrganization (WHO); advanced quality management at the water treatment
plants based on ISO9001; and the highly accurate water quality inspections
guaranteed by ISO/IEC17025. The water quality management at eachtreatment plant is as follows.
•Elaborate checking on the status of water treatment via water quality
meters and water quality tests•Conducting water quality tests for each parameter at an appropriate
frequency, such as daily, weekly, or monthly•••

Quality inspection of chemicals used in water treatment
Constant monitoring using a fish-based water monitoring tank
Other investigations and researches regarding water quality management(3) Water quality management at faucets
To confirm the safety of water supply at the point of faucets, water quality
inspections are conducted periodically at the 131 designated locations inTokyo for each water distribution network. The details on the water quality
management at each faucet are as follows.
•Automatic water quality meters are installed at all the 131 locations tocontinuously monitor the color, turbidity, and residual chlorine whose
measurement is required by the Waterworks Act once a day.

•

Water quality inspections are conducted at different frequencies ranging
from once to 12 times a year including for the 51 parameters of drinking
water quality standards, those for water quality management targets and3/7those for which further consideration is required.
In addition, the Bureau has set its own "Water Quality Targets for
Refreshing Water," which are at a higher level than the national standards,
and is implementing comprehensive measures to achieve those targets. Thefigure below shows the eight targeted parameters, whose values are being
measured at the 131 faucets.
(4) Irregular inspections in case of anomaly water quality detection
Irregular water quality inspections are conducted when there is a risk of
non-compliance with the drinking water quality standards because of ananomaly water quality or facility contamination detected somewhere fromsource to tap. Irregular inspections are implemented in cooperation withrelevant departments and municipalities to investigate the cause and find its
solution.
(5) Water quality inspections by request of customers
Inquiries from customers regarding water quality and their requests forwater quality inspections are handled, in the wards, through a cooperation of
the Customer Center, branch offices and the Water Quality Center, and in theTama area, through a cooperation of the Tama Customer Center, service
stations, and the Tama Water Supply Reform Promotion Division.
To further enhance water quality management at the Bureau, considering
the current situation in which the pollution of water sources is becoming more
complex and diverse, the utility is striving to acquire the latest analyticaltechniques and develop water treatment technologies, as well as to conductvarious researches and experiments.

Measures &Solutions(1) Responses to radioactive materials
The Great East Japan Earthquake of March 11, 2011 caused the Fukushima
Daiichi Nuclear Power Plant incident, which led to radioactive materials
having been detected in the tap water of the Bureau. The Bureau studied
methods to remove radioactive materials and implemented effective watertreatment. As a result, the utility confirmed that radioactive iodine can beremoved by a combination of appropriate chlorination and powdered
activated carbon treatment, and that radioactive cesium can be removed bycoagulation and sedimentation.
In terms of inspections, radioactive materials in water supply are measured
daily at five water treatment plants that represent the utility’s each water
source, and also measured periodically at other water treatment plants as
4/7

well as at the water treatment stations in the Tama area. The measurement
results are published on the Bureau’s website. Radioactive iodine has neverbeen detected since mid-April 2011, and radioactive cesium has never beendetected since its measurement started on March 22, 2011.
(2) Responses to the formaldehyde water quality incident
In May 2012, a major water quality incident took place that led to thesuspension of water intake and water supply in wider areas including Tokyo.
The incident resulted from the amount of formaldehyde exceeding thedrinking water quality standards having been detected in the tap water fromwater treatment plants using the Tone River system. At the Bureau, waterintake was suspended at the Misato water treatment plant. The incident wascaused by a certain substance that had not been regulated as a hazardous
substance having been discharged into the Tone River system without proper
treatment and afterwards having reacted with chlorine used for disinfection
at water treatment plants to produce formaldehyde. In the immediate
aftermath of the incident, the Bureau cooperated with water utilities in theTone River basin and investigated the origin of the water discharge while
reinforcing the monitoring of its water qualities.
(3) Responses to emerging chemical substances
In response to the formaldehyde water quality incident, the Ministry ofHealth, Labour and Welfare (MHLW) designated in March 2015 the substancesthat had not been subject to water discharge regulations but would produce
a high amount of formaldehyde and other harmful substances as a result of
the common water treatment process as the “substances difficult to treat withwater treatment”. The Bureau has carefully selected chemical substances,including the MHLW-designated ones, that can cause water source quality
incidents, and established their inspection methods. These substances havebeen studied for their removability in water treatment, and the research
results have been reflected in the TOKYO Advanced Quality Program.
(4) Measures against musty odor
In the past, musty odor in the Tama River and Sagami River was mainly
caused by cyanobacteria generated within reservoirs located upstream of therivers, but in recent years, musty odor originating from river waters
themselves has become an issue. In the Tama River, musty odor has been aproblem since 2011, and it has been detected in raw water above the level
permitted by the water quality standards. This has been caused bycyanobacteria attached to stones on the riverbed, and the same type of
5/7

cyanobacteria has also been causing musty odor in the upstream portion of
the Arakawa River since around 2012.
The Bureau has been investigating the causes and status of cyanobacteria
outbreaks, as well as conducting research and experiments on thesophistication of its water treatment process according to different raw water
qualities, and studying the potential use of more optimal water treatment
methods. At present, it is difficult to remove musty odor by the conventional
water treatment process, therefore powdered activated carbon has been
injected to address the issue at related water treatment plants, whileozonation has been reinforced at the treatment plants using advanced watertreatment process.
(5) Measures against cryptosporidium
Cryptosporidium, which is a zoonotic pathogen, is difficult to kill completelyby ordinary chlorination, but it can be removed by removing turbidity fromraw water through appropriate water treatment process. Based on theMHLW’s “Guidelines for Addressing Cryptosporidium in Water Supply”(published in March 2007 and revised in May 2019), the Bureau has set out
how the utility addresses cryptosporidium in its "TOKYO Advanced Quality
Program"(6) Measures against eutrophication in Ogouchi reservoir
When high concentrations of nitrogen, phosphorus, and other substances
contained in domestic wastewater flow into reservoirs, algae that use themas nutrients grow in mass quantities, causing odor and taste issues as well as
filtration problems at the water treatment plants taking water from therelated water sources. In the case of the Ogouchi reservoir, algae bloom (aphenomenon in which lake surfaces look like they are covered with blue
powder due to algae growth) occurs mainly during summer in the upstreamportion of the river. The Bureau has protected the reservoir’s water quality by
installing fences to prevent the spread of the bloom, in addition to thedevelopment of wastewater facilities.
(7) Research and experiments
Various researches and experiments to develop and improve water
treatment technology have been conducted at the Training and Development
Center and the Water Quality Center. The research results have been
published on the utility’s website.
Future Plans

The Bureau will continue to maintain a reliable water quality inspection
system and elaborate water quality management structure from source to6/7

tap, and will also proactively address emerging water quality issues throughvarious researches and experiments in order to supply safe and refreshing tap
water to its customers.
The following three documents were referenced from the website of theBureau of Waterworks Tokyo Metropolitan Government(https://www.waterworks.metro.tokyo.jp/).
- “Service Outline: FY2019.” September 2019.
- “Water Supply of Tokyo.” September 2019.
- “Water Quality Inspection Plan for FY2019.” March 2019.

References

Additional information on the types and number of water sources of theBureau is as follows.
- Surface water: Tone River, Arakawa River, Edo River, Tama River, Sagami
River- Groundwater: wells (including those currently suspended)- Subsoil water: Kinuta and Kinuta-shimo, Takatsuki, Hyuga-wada, Chigase
No. 1 and No. 2, Futamatao, Sawai No. 1 and No. 2, Mitakesan, Nariki- When allocated by the number of water treatment plants (76): surface
water (17), groundwater (48), subsoil water (11)

7/7