In Japan, extension of sewer network is measured by the indicator of sewer service accessibility ratio (SSAR).
Its denominator is the number of registered citizens in the total area of governments, such as nation, region, prefecture, and municipality.
Its numerator is the number of registered citizens in the serviceable area.
There is not sanitary or combined sewer network without a treatment plant.
The current discussion is what the final goal of SSAR should be.
The National SSAR reached 72.7% by the end of fiscal year 2008, that is March 31, 2009.
The SSAR excludes on-site sewage treatment system and small sewer system for farmers’ community.
If they are included, the ratio is 84.8%.
The inclusive ratio is called sewage treatment accessibility ratio.
Do we have to continue to install sewer?
Population is on the decrease.
The remaining area without sewer is suburb.
Therefore, installation of sewer becomes inefficient.
Governments are heavily indebted.
Stop costly sewer expansion projects by public.
Instead spread on-site systems by subsidizing home owners.
This is a critical opinion which a municipality with sewer expansion projects faces.
The refutation is as follows.
On-site system is difficult to maintain to produce high quality effluent especially if nutrient removal is required.
It needs space to install, one car park at minimum.
Some houses are too small to install on-site system.
It needs drainage channel from individual property to public waters.
It needs periodical desludge by vacuum truck for good.
It needs treatment facility to dispose of the sludge.
Therefore, comparison of only installation cost of sewer versus on-site system is misleading.
Jun 26, 2010
Sewer rate principle
Sewer rate is decided by a principle in Japan.
The principle is that sanitary sewage cost shall be borne by users while storm water by the public.
Cost bearing by the public means input of general tax.
Therefore, sewer management is paid by a combination of user charge and general tax.
In some cases of combined sewer, the cost is allocated to users and general tax by the design flow.
The flow of storm water is much greater than that of sanitary sewer.
Therefore, municipalities with more combined sewers receive more money from general tax than those with only sanitary sewers.
The principle is that sanitary sewage cost shall be borne by users while storm water by the public.
Cost bearing by the public means input of general tax.
Therefore, sewer management is paid by a combination of user charge and general tax.
In some cases of combined sewer, the cost is allocated to users and general tax by the design flow.
The flow of storm water is much greater than that of sanitary sewer.
Therefore, municipalities with more combined sewers receive more money from general tax than those with only sanitary sewers.
Jun 19, 2010
Benefit Principle Charge
Most municipalities take benefit principle charge system.
Beneficiaries, mostly landowners, have to pay their due after sewer service becomes available.
This is based on the idea that availability of sewer service increases the value of land and part of the increased value should be returned to the public.
The benefit charge system is authorized in the national law for urban planning.
The details of charge system are decided by municipal law.
The charge amount depends on the size of land.
In case of Saitama City, the latest unit charge is 810 yen/m2.
It is calculated based on the sewer installation cost.
The process of charge is as follows.
1 Public notice for commencement of sewer service on quarterly basis
2 Public notice for benefit principle charge for the land where sewer service has become available in the previous fiscal year in early April
3 Send letters to land owners for confirmation on payment in early April
4 Send bills in early June
5 Payment by land owners in quarterly installments for 5 years, which is 20 times in total
Beneficiaries, mostly landowners, have to pay their due after sewer service becomes available.
This is based on the idea that availability of sewer service increases the value of land and part of the increased value should be returned to the public.
The benefit charge system is authorized in the national law for urban planning.
The details of charge system are decided by municipal law.
The charge amount depends on the size of land.
In case of Saitama City, the latest unit charge is 810 yen/m2.
It is calculated based on the sewer installation cost.
The process of charge is as follows.
1 Public notice for commencement of sewer service on quarterly basis
2 Public notice for benefit principle charge for the land where sewer service has become available in the previous fiscal year in early April
3 Send letters to land owners for confirmation on payment in early April
4 Send bills in early June
5 Payment by land owners in quarterly installments for 5 years, which is 20 times in total
Painted Manhole Cover
In Japan, many sewer operators use manhole covers with the city's symbols.
It is for raising awareness of sewer among citizens and for urban landscaping.
In case of Saitama City, two kinds of covers are used.
They are a combination of city symbols that include a tree, a flower grass, and a flower tree.
The tree is a zelkova, the flower grass is primrose, and the flower tree is a cherry tree.
This is a manhole for combined sewers and sanitary sewers.
This is for storm sewers.
It is for raising awareness of sewer among citizens and for urban landscaping.
In case of Saitama City, two kinds of covers are used.
They are a combination of city symbols that include a tree, a flower grass, and a flower tree.
The tree is a zelkova, the flower grass is primrose, and the flower tree is a cherry tree.
This is a manhole for combined sewers and sanitary sewers.
This is for storm sewers.
Jun 12, 2010
Prevention of Manhole Floating
Earthquake is a matter of life and death in Japan.
Sewerage is no exception.
Underground structures are susceptible to liquefaction especially if they are in sand with high water table.
Manholes are the weakest1).
Three solutions are proposed in the national guideline for new manhole installation2).
They include 90% compact fill with sand, filling with soil cement, or filling with gravel.
For the existing manholes, there are several proposed technologies.
Here is an example with experimental demonstration3).
It uses metal weight to cope with buoyancy.
Metal weight is put in the frame fastened around a manhole.
In the experiment, without the weight, manhole came up out of ground.
With the weight, the manhole stayed in the ground.
The videos are on this site; http://www.fmhk.jp/product1.php?p=2.
1)http://ja.wikipedia.org/wiki/%E3%83%95%E3%82%A1%E3%82%A4%E3%83%AB:%E5%B0%8F%E5%8D%83%E8%B0%B7%E5%B8%82%E3%81%AE%E6%B6%B2%E7%8A%B6%E5%8C%96%E7%8F%BE%E8%B1%A1.jpg
2)http://www.mlit.go.jp/common/000026846.pdf
3)http://www.fmhk.jp/
Sewerage is no exception.
Underground structures are susceptible to liquefaction especially if they are in sand with high water table.
Manholes are the weakest1).
Three solutions are proposed in the national guideline for new manhole installation2).
They include 90% compact fill with sand, filling with soil cement, or filling with gravel.
For the existing manholes, there are several proposed technologies.
Here is an example with experimental demonstration3).
It uses metal weight to cope with buoyancy.Metal weight is put in the frame fastened around a manhole.
In the experiment, without the weight, manhole came up out of ground.
With the weight, the manhole stayed in the ground.
The videos are on this site; http://www.fmhk.jp/product1.php?p=2.
1)http://ja.wikipedia.org/wiki/%E3%83%95%E3%82%A1%E3%82%A4%E3%83%AB:%E5%B0%8F%E5%8D%83%E8%B0%B7%E5%B8%82%E3%81%AE%E6%B6%B2%E7%8A%B6%E5%8C%96%E7%8F%BE%E8%B1%A1.jpg
2)http://www.mlit.go.jp/common/000026846.pdf
3)http://www.fmhk.jp/
Water Reclamation
In Japan, water is often reclaimed under sustainable city philosophy for land development projects.
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
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
Jun 6, 2010
Interior Drainage Flood Control_03
The details of South URAWA Relief Sewer Second are in the following pictures1)2).
It is necessary to avoid other utility lines while not causing damage to structures such as bridge foundations in the downtown.
This leads the relief sewers to be placed deeper and deeper and the costs higher and higher.
1) http://www.city.saitama.jp/www/contents/1189057832553/files/minamiku1.pdf
2) Construction Works of South URAWA Relief Sewer Second, Brochure, Saitama City & Kajima Corporation
It is necessary to avoid other utility lines while not causing damage to structures such as bridge foundations in the downtown.
This leads the relief sewers to be placed deeper and deeper and the costs higher and higher.
1) http://www.city.saitama.jp/www/contents/1189057832553/files/minamiku1.pdf
2) Construction Works of South URAWA Relief Sewer Second, Brochure, Saitama City & Kajima Corporation
Interior Drainage Flood Control_02
In most cases, runoff needs to be drained to rivers by sewers.
In some, it is drained to lakes and seas.
Urban rivers lack flow capacity to accommodate all the urban runoff in strong rainfalls.
Urbanization has caused runoff increase and difficulty in expansion of capacity.
Many bridges with heavy traffic of cars and trains are already over the rivers.
Many houses and buildings are along the rivers1).
Those existing structures have to be relocated for expansion works.
It is almost impossible as negotiation with property owners is very difficult.
There is no open land for detention ponds.
Therefore, relief sewers are needed to detain runoff under the roads although costly.
The roads are only space available for runoff detention.
Under this situation, Saitama City constructed and completed a relief sewer in 2009.
It is called South URAWA Relief Sewer Second.
It has a capacity of 40,000m3 for storage.
It is 13 to 23m below ground, 4.75m across, and 2,260m long.
It runs busy downtown like this picture2).
1) http://www.yamaiko.com/touring/20070204.html
2) Construction Works of South URAWA Relief Sewer Second, Brochure, Saitama City & Kajima Corporation
In some, it is drained to lakes and seas.
Urban rivers lack flow capacity to accommodate all the urban runoff in strong rainfalls.
Urbanization has caused runoff increase and difficulty in expansion of capacity.
Many bridges with heavy traffic of cars and trains are already over the rivers.
Many houses and buildings are along the rivers1).
Those existing structures have to be relocated for expansion works.
It is almost impossible as negotiation with property owners is very difficult.
There is no open land for detention ponds.
Therefore, relief sewers are needed to detain runoff under the roads although costly.
The roads are only space available for runoff detention.
Under this situation, Saitama City constructed and completed a relief sewer in 2009.
It is called South URAWA Relief Sewer Second.
It has a capacity of 40,000m3 for storage.
It is 13 to 23m below ground, 4.75m across, and 2,260m long.
It runs busy downtown like this picture2).
1) http://www.yamaiko.com/touring/20070204.html
2) Construction Works of South URAWA Relief Sewer Second, Brochure, Saitama City & Kajima Corporation
Jun 5, 2010
Interior Drainage Flood Control_01
Urbanization has caused runoff increase.
The pictures show progress of urbanization at Westside of Omiya Station1).
In Saitama city, the runoff ratio has risen from 40% around 50’s to 60% in 2007.
In addition, climate change or urban heat island may have increased weather extremes.
Extreme rainfall events of 50mm/hr or over have increased in Saitama City.
In 10-year period from 1997 to 2006, the number was nine.
Out of this nine, four events were observed in 2005 & 2006 alone1).
Urbanization and extreme rainfalls have been raising the vulnerability to flood2).
1) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku01.pdf
2) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku03.pdf
The pictures show progress of urbanization at Westside of Omiya Station1).
In Saitama city, the runoff ratio has risen from 40% around 50’s to 60% in 2007.
In addition, climate change or urban heat island may have increased weather extremes.
Extreme rainfall events of 50mm/hr or over have increased in Saitama City.
In 10-year period from 1997 to 2006, the number was nine.
Out of this nine, four events were observed in 2005 & 2006 alone1).
Urbanization and extreme rainfalls have been raising the vulnerability to flood2).
1) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku01.pdf
2) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku03.pdf
Improvement of River Quality by Sewerage Expansion
This graph1) shows the effectiveness of sewerage system for water pollution control.
As sewer service with treatment grows, BOD of the rivers reduces.
Kamo, Shiba, and Ayase Rivers run through the downtown of Saitama City.
These pictures2) show the rivers before and after sewerage service is in place.
Without sewerage service, the KAMO River was full of foams by untreated sewage.
The left picture was taken in 1978 and the right in 2007 at the same place.
1) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku01.pdf
2) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku03.pdf
As sewer service with treatment grows, BOD of the rivers reduces.
Kamo, Shiba, and Ayase Rivers run through the downtown of Saitama City.
These pictures2) show the rivers before and after sewerage service is in place.
Without sewerage service, the KAMO River was full of foams by untreated sewage.
The left picture was taken in 1978 and the right in 2007 at the same place.
1) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku01.pdf
2) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku03.pdf
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