1. Why Sewage Works is Essential to Cities?
2. Current Situation of Sewage Works in Japan
Major Objectives of Sewerage Systems and New Tasks for Future
3. Treatment plants
4. Bodies to Implement Sewage Works
5. Infrastructure Intensive Development Plan

6. Partial Amendment of Sewerage Law
7. Amendment of Enforcerment Order of Sewerage Law
8. Reuse of Treated Wastewater
9. Reuse of Sewage Sludge
10. Utilization of Uppe‚’ Space of WTP and Inside of Sewer Pipe
11. Advanced Wastewater Treatment
12.Trenchless Technology
13.Combined Sewer Overflow (CSO) Control
Advantages and Disadvantages of Combined Sewer Systems
14.Effective Utilization of Digester Gas
Biomass, Environment - Friendly Alternative Energy Resource

15. Stromwater control in urban area
Development of Safety City for Heavy Rain

1. Why Sewage Works is Essential to Cities?
When we develop cities, the cities have sanitation problems.
To solve the problems sewage facility is the effective answer.
Japan has made a great effort for installing the sewer system.
In 1901 the Sewerage Law was enacted and in 1970 it was
revised, as it was recognized that sewers were indispensable
in maintaining water quality of public water bodies clean.

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2. Current Situeation of Sewage Works in Japan
Sewage works has been promoted intensively and systemically
based on "Five-Year Program for the Sewerage Construction"
and recently "Infrastructure Intensive DevelopmentPlan".
Through these programs, the sewered population rate has become
68% in FY.2004

The percentage of sewered population is shown in (Figure-1).

As the progress of sewage works, we have been gradually able to
accomplish the major objectives of sewerage system such as flood
control, improvment of living condition, and preservation of water
quality. In addition to principle objectives of sewerage systems,
we are facing new tasks for future, coming along with the
promotion of sewage works

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3. Treatment Plants
The types of processes used at sewage treatment plants in Japan
are shown inthe (Table-3).
Of the 1622 treatment plants, 693 sites adopt conventional activated
sludge process.

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4. Bodies to Implement Sewage Works
The sewage works in Japan are implemented mainly by Ministry of
Land Infrastracture and Transport (MLIT), Prefectures and
Municipalities, and
Japan Sewage Works Agency (JS).
Regording the main roles and activity of these organization, please
refer to following page.

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5. Infrastructure Intensive Development Plan
Infrastructure Intensive Development Plan including sewerage
facilities was decided by cabinet on Oct. 10, 2003.
In this plan, principal objects and target outcome in 2007 for each
facilities like roads, airports, rivers, etc., as well as sewerage facilities,
were set up to promote the project intensively and effectively.
In the field of sewage works, five principal objects and relating targer
outcome were decided.
In detail of this plan, please refer to following page and
SBMC Newsletter Vol.1 No.4.

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6. Partial Amendment of Sewerage Law
Partial amendment of Sewerage Law was made on June 2005, and
came into forth in November 2005.
In this amendment, promotion of advanced wastewater treatment,
establishment of regional flood control system and immediate
response to the accident when toxic substances flow into
wastewater treament plant were formulated to cope with recent
important issues such as safety improvement of the lives of people
and preservation of global environment.
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7. Amendment of Enforcement Order of Sewerage Law
The sewerage systems in Japan have been planned, constructed,
managed and maintained based on the Sewerage Law.
Regarding the law, partial amendment was made on the Enforcement
Order of the Sewerage Law on September 2003 and came into forth in
April 2004
In this amendment, the necessity and target of CSO controls have
become clear, and the technical standards for final effluent water
quality have been reinforced.
In detail, please refer to following page and SBMC Newsletter
Vol. 2, No2

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8. Reuse of Treated Wastewater
Treated wastewater is a valuable water resource in urban area,
and its amount will increase with the progress of sewered
population rate.
In urban area where population is so concentrated and it is very
difficult to secure water resources, reuse of treated wastewater
is one of the effective countermeasures for water shortage.
In 2001, in 218 WTPs the treated wastewater is transported to the
outside of WTPs and reused as industrial water, water for
landscape use and so on, and its amount was approximately 190
million m3 per year.
The present status of reuse of Treated wastewater is shown in
following web page.

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9. Reuse of Sewage Sludge
In sewerage systems, sewage sludge is inevitably generated
through wastewater transportation and treatment. Appropriate
treatment and disposal of generated sludge is essentially
important for national maintenance and operation of sewerage
The amount of generated sludge in Japan has increased year by
year in proportion to growing sewered population rate, and it
reached 2.1 million Dry-solid ton throughout the year in 2002.
On the contrary, the available capacity of sanitary land fills for
sludge disposal is insufficient becouse of increasing amount of
wastes with the progress of social economy and difficulties to
to secure and construct new dump yards.
To deal with the shortage of sanitary land fills area, continuous
efforts to establish and promote the Recycling-Based Society are
needed in the field of sewage works.
The present status of reuse of Sewage Sludge is shown in
following web page.

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10.Utilization of Uppe‚’ Space of WTP and Inside of Sewer Pipe
Sewerage Systems create a useful recourse such as treated
wastewater, valuable water resource in urban area and sewage
sludge, new biomass energy resource.

Also, upper space of covered Wastewater Treatment Plant and
Pumping Station is valuable open space in overcrowded city, and the

inside of sewer pipe is now effectively used for Optical Fiber Cable


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11. Advanced Wastewater Treatment
Secondary treatment removes mainly organic matter and suspended
solid in wastewater. However, in some area, especially in closed
water body such as inner bays, semi-enclosed seas, lakes and
reservoirs, secondary treatment level has been insufficient to
protect the receiving waters.
In these areas, the load of inflowing pollutants is large and
pollutants tend to accumulate.  There has been progress of
eutrophication caused by inflowing nutrients such as nitrogen and
phosphorus, which acceleratedthe deterioration of water quality.
Thus, advanced wastewater treatment or additional treatment
step to remove further organic matter and suspended solids
and/or to provide for removal of nutrients such as nitrogen
and phosphorus has been needed for removal of nutrients
for prevention of eutrophication, achievement of water quality
standard water quality preservation in water supply source,
reuse of treated wastewater, etc.
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12.Trenchless Technology
The city life in urban area is supported by lifeline such as
sewerage system, water supply system, city gas, electricity and
electrical communication, and most of them consist of buried
pipe in the ground. The burial methods for these lifelines include
the open-cut method and the trenchless method.
The open-cut method has problems like traffic congestion, street
pavement damage, cost of surface damage, etc. Then, it is often
difficult to be adopted in overcrowded city.
Trenchless method includes the shield method and the pipejacking
method, and these methods need excavating less area of the
ground surface compared to the open cut method. Therefore,
trenchless method is excellent concerning the urban
environment measures such as: reduction of the area used
for the construction; reduction of the public nuisance caused by
the construction including noises, vibration, dusts; and reduction
of influence on traffic and citizens' living.
In detail of Trenchless Technology, please visit following web page.

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13. Combined Sewer Overflow (CSO) Control
There are two types of sewage (rainwater and wastewater) collection
systems, namely, separate sewer system and combined sewer systems.

Combined sewer systems (CSS) have only one pipe which conveys

both wastewater and stormwater to a local wastewater treatment
In combined sewer systems, flood control and water quality
preservation in public water bodies can be expected by construction
of one pipe.
Therefore, combined sewer systems widely adopted in large cities
such us Tokyo, and Osaka where sewage works were promoted
in early stage. In these areas, flood control and wastewater
drainage had to be accomplished at the same time.
However, during heavy rain event, overflows occur from these combined
sewers which results in stormwater runoff and sewage being discharged
into water bodies. As design capacity of sewer systems is limited, the
exceed sewage including rainwater and wastewater is discharged to
public water bodies from outlet installed in sewer systems.
Therefore, in the case of CSS, Combined Sewer Overflow (CSO) should
be appropriately controlled to preserve the water quality in water bodies.

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14. Effective Utilization of Digeater Gas

Biomass, plant and animal matter providing power or energy, which
is carbon neutral and renewable organic resource, is very effective for
prevention of global warming and promotion of a recycling-oriented
society, and its utilization is strongly required.

Digester gas, one of the useful biomass produced by anaerobic digestion

in Wastewater Treatment Plant has been utilized as a fuel for boilers
which is used for heating of digestion tank, and excess digester gas has
not been utilized but only burned using gas burning equipment.
However, recently, effective measures for utilization of excess digester
gas have been established and digester gas is widely and effectively used
in Japan. In this report, effective utilization of digester gas is explained.

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15. Stromwater control in urban area

One of the essential roles of Sewerage Systems is stormwater drainage.

Efficient stormwater drainage control is needed to secure citizen's
life and property against flooding and contribute to the sound urban

In Japan, "Development of Safety City for Heavy Rain" is one of

important target outcomes in "Infrastructure Intensive Development
Plan" formulated by Ministry of Land Infrastructure and Transport.
In recent year, total amount of stormwater runoff has been increasing
because of reduction of permeable area by urban development.
Therefore, rational Stromwater control in urban area is requested.

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