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◆Reconstruction of Facilities
Ward area sewerage operations began during the Meiji era and the sewer diffusion rate reached 100% in FY1994.
However, facilities built during the early years are deteriorating.
In order to provide constant sewerage services to our customers for years into the future, while attempting to
extend the life of existing facilities, we are reconstructing them in order to improve rainwater removal capability,
energy efficiency. |
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●Reconstruction of Sewers
We extend service life through repairing to enable planned rebuilding. |
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Extending the length of the districts sewer pipes
The total length of sewer pipes that has exceeded
their 50-year legal service life has now reached
1,500 km and is rapidly increasing.
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How Sewer Reconstruction Works
TV camera inspections are used to evaluate for damage and rainwater discharge capability. Healthy pipes are left alone, while pipes with light damage are strengthened from within using trenchless sewer rehabilitation methods, which require no road excavation. New pipes are laid when a pipe has insufficient capacity. |
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Sewers before reconstruction
The deterioration in concrete surface and corrosion of
reinforcement steel is lowering the strength of sewer pipes.
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Sewers that are being rebuilt
Sewer pipes are being strengthened by lining them with
rigid vinyl chloride material. This enables low-cost renewal
since streets do not have to be ripped up. |
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●Reconstruction of Water Reclamation Center and Pumping Stations
In addition to deterioration-control measures, there will be reconstructing to improve functionality such as better earthquake protection and greater capacity to whisk away rainwater.F0e0ca |
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◆Flood Countermeasures
Based on Tokyo City's basic policy for dealing with stormwater, the city has been building sewer facilities that
will be able to handle 50 mm precipitation during one hour over all wards. Especially, in 20 areas prone to
flooding, a 10-year plan to make such areas withstand 50 mm precipitation lasting one hour started in 2008.
In 9 areas with large underground shopping malls where damage caused by flooding could be enormous, we are
overhauling storage facilities that can store stormwater from 75 mm precipitation lasting one hour. We are also
working with related agencies and wards to control runoff. |
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| Stormwater pipe construction |
Stormwater regulating reservoir construction |
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◆Improvement of Combined Sewer System
In combined sewers, rainwater is carried together with sanitary sewage. This mixed wastewater is sometimes
released to waterways when rainfall exceeds a certain level. The Bureau is enhancing trunk sewers and storage
facilities to reduce such releases and help maintain the water quality of rivers and the sea. |
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In 14 water districts with little water or that are closed water body, storage tanks and other facilities will be construction. |
 Discharges from rainwater outlets
The Bureau is implementing improvements to
its combined sewer system to reduce the
amount of sanitary waste discharged into
waterways during rainy weather, increase the
treatment volume of water reclamation centers
through enhancement of trunk sewers, and
improve facilities to suppress the release of
debris and oil balls from sewer outlets. We are
also upgrading reservoirs for storing sanitary
sewage when rainfall begins so that it can then
be sent to a water reclamation center for
treatment after rainfall. |
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◆Advanced Treatment
Construction of the sewerage system has greatly improved water quality of rivers and the sea, but red tides still
occur for 90 days of the year at Tokyo Bay. As the measure towards this phenomenon, we are introducing
advanced treatment facilities to eliminate large amounts of nitrogen and phosphorus.
Since advanced treatment needs large scale of facility, there are some water reclamation centers where such
process cannot be readily installed. At such centers, we are combining improvement of the existing facilities and
optimization of operation and management. That will enable installation of semi-advanced treatment, which can
enhance removal rate of nitrogen or phosphorus. These efforts will improve further the quality of treated
wastewater released into the Sumida River and the Tokyo Sea. |
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Use of reclaimed water
