Newsletter and Technical Publications
Freshwater Management Series No. 10
Managing Urban Sewage
An Introductory Guide for Decision-makers
Bureau of Sewerage, Tokyo Metropolitan Government
The construction of modern sewerage in Tokyo dates back to 1884, when a horseshoe-shaped
bricklaying sewer was installed in the downtown area named Kanda, a part of the pipe is stillin use and
is monumentally called the "Kanda Sewer".
Some 110 years after the Kanda Sewer was laid, the sewerage system in the ward area, which is the
metropolis area, provided service to almost 100% of the population by the end of March 1995. And the
regional sewerage system in suburban Tokyo area, "Tama area" covered 93% of the population by the
end of March 2002.
There are thirteen treatment plants in the ward area, which receive approx. 4.6 million tons of wastewater
every day, and seven plants in "Tama area" receive approx. 0.86 million tons.
The role of sewerage in Tokyo has changed and expanded in scope from age to age with changes
in socioeconomic conditions, metropolis structures, and the environment.
Its fundamental roles at present are:
(1) Improving the living environment by drainage and disposal of wastewater;
(2) Preventing inundations through removal of rainwater;
(3) Preserving the quality of public water bodies.
And also, sewerage performs many other roles. It enhances water environment through recycling and
advanced treatment of wastewater, conversion of sludge into resources, thermal energy is extracted from
sewerage by such methods as tapping the heat in wastewater, and optical fiber communication cable
channels are furnished.
In addition to these, Bureau of Sewerage, T.M.G. is carrying out the following projects as priorities
to implement a desirable sewerage system in the 21st century.
|(1)||Reconstruction; Part of Tokyo’s sewers has deteriorated due to aging and external physical
disturbance such as unexpectedly heavy traffic above, ground subsidence, and so on. At
present, the length of the sewers, which have exceeded legal service life, is about 2,000km and this
number will continue to grow in future. Also, some plants have difficulties to cope with the increase
of the flow of wastewater and rainwater due to improvements in living standards and land use.
Therefore, reconstruction has been promoted by rehabilitating the deteriorated facilities, increasing
the insufficient capacities, and upgrading of functionability.|
|(2)||Inundation Control; In recent years, inundation has occurred even in sewered urban areas. The
cause is the fact that the land surface is covered with buildings, pavement and other structures. As a
result, rainwater does not infiltrate to the ground and large amounts of rainwater that exceed
capacity runs off and overflows. In order to prevent the inundation, the capacity of sewers and
pumping stations needs to be augmented and the construction of rainwater storage tanks is necessary.|
|(3)||Improvement of combined sewer system; In the combined sewer system, which serves 82% of the
total area, both rainwater and wastewater runs in the same pipe during wet weather, and in case of
heavy rain, part of this overflows into the receiving waters without treatment. This is called
and poses a serious problem in preserving the water quality of public water bodies. Expansion of
CSO intercepting sewers to wastewater treatment plants and installation of CSO storage tanks are
being implemented for the countermeasures.|
Bureau of Sewerage, T.M.G. obtained ISO14001 "the Environmental Management
in its all departments and offices by December 2002. Bureau of Sewerage, T.M.G. is dedicated to create
desirable water environment in Tokyo and transfer it to future generations through the daily activities
||For more information contact:
Sewerage Bureau, Tokyo Metropolitan Government
Address: 2-8-1 Nishi-shinjuku, Tokyo, 163-8001,Japan
Tel: +81-3-5320-6515 Fax: +81-3-5388-1700