This is an example of water reclamation in Japan.
It is Kamiochiai & Kishiki Stormwater Detention Tanks at Saitama New Metropolis1).
The Saitama New Metropolis (SNM) was designated as business and government center by national government in 1988 in order to complement capital Tokyo2).
The SNM lies mainly on a former coach yard of Japanese National Railways (JNR) and a private company's former factory site.
The coach yard stopped its operation in 1984.
The JNR was under the arms of national government.
It was privatized into six regional passenger service companies and one freight car company in 1987.
In 2000, the SNM opened after a series of redevelopment and zoning projects.
It is now the business center in Saitama Prefecture with lots of government and company offices.
SNM follows the principles of sustainable city below.
-Water; efficient use of water resource, reduction of intensification of water cycle, less pollution by development.
-Solid Waste; reduction, recycling, reuse and proper disposal to lessen the harmful effect on environment outside SNM
-Energy; efficient use, clean energy use, energy save to create eco-friendly city
In line with the principles, wastewater service operators, Saitama City (SC) and Saitama Prefecture (SP), reclaim wastewater.
SC reclaims stormwater (STW) for landscaping and recreational stream, while SP does sanitary wastewater (SW) for non potable use of toilet flush water (TFW) by advanced treatment (AD) of effluent of SC’s wastewater treatment plant (WWTP).
These reclamation projects were subsidized by national government.
The runoff of rainfall on SNM is drained into Shiba River on the eastside and Kohnuma River on the westside by the pumps at constant flow rates according to the capacity of levees of the receiving rivers after being stored in each detention tank.
The tanks are under the roads to fully utilize public space.
The SDT volume are 37,000m3 on eastside and 40,000m3 on westside.
The flood recurrence interval was decided to be as long as10-year, which is 73.8mm/hr, for stormwater drainage design in SNM, considering the consequence of flood in the metropolis.
The interval of the rest of the city is 5 year.
A part of stormwater collected in the detention tanks is stored in the retention tanks.
The stored stormwater is reclaimed for landscaping and recreational stream in SNM after a series of treatment processes.
1) Kamiochiai & Kishiki Stormwater Detention Tanks at Saitama New Metropolis, brochure, Saitama City
2) http://ja.wikipedia.org/wiki/%E3%81%95%E3%81%84%E3%81%9F%E3%81%BE%E6%96%B0%E9%83%BD%E5%BF%83
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