




	1.	History
	The construction of sewerage systems in Tokyo dates back to 1884,
	when the Sewer System in Kanda District was constructed, and this
	was Japan's first project for modern sewerage systems.

	About 110 years after the Kanda Sewer Works, as of the end of March
	1995, the sewered population rate in Tokyo reached essentially 100%
	in 23 Ward Areas of which population is about 8.5 million.


	Kanda Sewer	Sumida River


	Tokyo Metropolitan Government, TMG, also carries out the construction
	and management of sewerage systems for cities and towns in Tama Area
	of which total population is about 3 million, and the sewered population
	rate in this area reached 97% in 2004.

	With the progress of sewage works, the water quality in Sumida River,
	which runs through Tokyo Metropolitan Area, has been greatly improved,
	though the water quality in the Sumida River was seriously deteriorated
	due to the economic growth in Japan in 1960's


	Fig Water Quality of the Sumidagawa Rivver and Sewerage Construction


	2.	Role of Sewerage Systems
	The role of sewerage systems has changed and broadened in scope from age
	to age with changes in socioeconomic conditions, city structures, and
	environment. The fundamental roles at presentare:
	1)	Improving the living environment by drainage and treatment of
		wastewater
	2)	Preventing floods through removal of rainwater
	3)	Preserving the water quality of public bodies

	In addition to these fundamental roles, sewerage systems are expected to
	perform additional other roles. A rich and comfortable water environment
	should be performed through the promotion of sewage works, and TMG conducts
	several new sewerage projects such as reuse of treated wastewater, advanced
	wastewater treatment, conversion of sludge into resources, utilization
	of thermal energy contained in wastewater as a heat source using heat
	exchange technology, optical fiber communication cablechannels installed
	in the upper part of sewer pipes.


	Recently, Ariake Wastewater Treatment Plant, WTP, one of the newest WTP
	in TMG, has started its operation, and it has been characterized by advanced
	wastewater treatment, pressure wastewater collection system, utilization
	of upper space on the roof of covered WTP as playground, ozone-treated
	wastewater, etc.


	Ariake Treatment Plant

	3.	Major policies
	Sewerage Systems perform an important role as a fundamental infrastructure
	that supports sound and civilized urban life and activities, and present
	TMG's major policies for Sewerage Systems are as follows.

	1)	Reconstruction
	Tokyo's sewer, which has been constructed for the past 120 years, has
	deteriorated due to aging and external influences. At present, the total
	length of the sewers, which have exceeded legal service life, is about
	2,000km mainly in the center of Tokyo, and it is about 13% of the total
	length.
	Under these circumstances, TMG has promoted reconstruction and
	renovation of sewerage systems. In conjunction with reconstruction,
	improvement of capacity of sewer system and/or WTP, introduction of
	advanced wastewater treatment, multi-purpose uses of resources and
	facilities like Ariake WTP, etc. have been performed.

	2)	Inundation Countermeasures
	Sewerage Systems are very effective for flood control.　However, even
	in sewered areas, floods have occurred in recent years.　The cause of
	increased occurrence of the floods in urban area is the reduction of
	rainwater permeable area by increase of roads, houses, buildings, etc.
	and increase of stormwater runoff due to rapid urbanization. Floods
	caused in this situation are called "urban flooding".
	To cope with urban flooding, TMG has carried out several projects with
	following measures.
	(1)	To augment the capacity of sewers and pumping stations and
		construct rainwater storage tanks in areas where the rainwater
		runoff exceeds the capacity of existing sewers.
	(2)	To promote installation of rainwater storage and infiltration
		facilities to control the inflow of existing sewers.

	3)	Improvement of Combined Sewer System
	In the combined sewer system, which covers 82% of the total planning area
	in Tokyo, both rainwater and wastewater are transported in the same pipe
	during wet weather, and part of this is discharged into receiving water
	bodies without treatment. This is called Combined Sewer Overflow, CSO and
	it causes serious water quality problems.

	To cope with CSO problems, TMG is now expanding intercepting
	capacity from the present double volume of dry weather to triple
	to increase the volume of wastewater guided to the WTP.

	Moreover, a CSO storage tank is installed to prevent polluted first flush,
	which occurs in the early stage of rainfall. TMG are sldo installing
	screens to prevent rubbish, etc. at the rainwater outlets.


	Fig. Improvement of Combined Sewer System
	(Installation of Combined Sewer Overflow Storage Tank)


	In addition to these policies, TMG recently has promoted the
	prevention of global warming. In February 2005, Kyoto Protocol
	came into force, and for Japan, by 2012 greenhouse gases volume
	should be reduced to 94% volume, which were exhausted in 1990.
	To achieve the goal of the Kyoto Protocol, Bureau of Sewerage
	in TMG has progressed to adopt the energy saving technology
	such as utilization of unused energy, reduction of the green
	house gas emission from sludge incinerator, and so on.

	4.	Training Project in Asian Network of Major Cities 21
	The Asian Network of Major Cities has been established to deepen social
	and economic bond and cooperation among Asian major cities, which are
	geographically close, have close cooperative ties in economic
	relationships and share many common cultural characteristics. It is
	expected to make a significant contribution to the prosperity and
	development of Asia in the 21st century through the network.
	Participating cities of the network are capital cities and major
	cities in Asia, and themes to cooperate on are Environment,
	Women's development, Issues of urban planning, Health, Human resource
	training, and so on.

	Please refer to	http://www.chijihon.metro.tokyo.jp/asianet/indexe.htm

	Bureau of Sewerage in TMG, conducts training project, Training Sewerage
	Maintenance and Management Engineers (Short-term and Long Term Course) as
	a part of activities of Asian Network of Major Cities 21, ANMC 21 in
	cooperation with JICA.

	5.	Closing
	Tokyo's sewage works are required to flexibly meet environmental
	changes, respond to diverse needs of residents in Tokyo by protecting
	and supporting daily lives, and contribute to the development of recycling
	society that harmonizes with the environment. Based on these social
	environment and needs, TMG will continue to promote sewage works, which
	perform diverse roles.

	We, TMG, hope you will visit our following web site, and get useful
	information from Tokyo
	http://www.gesui.metro.tokyo.jp/english/english.htm

	Tokyo Metropolitan Government,
	Bureau of Sewerage
	Mr. Kazuyoshi Motoda


	Tokyo Bay