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| 1. Why Sewage Works is Essential to Cities? |
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| 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 |
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| 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 |
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| The percentage of sewered population is shown in (Figure-1). |
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| 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 |
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| The types of processes used at sewage treatment plants in Japan |
are shown inthe (Table-3).
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| Of the 1622 treatment plants, 693 sites adopt conventional activated |
| sludge process. |
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| 4. Bodies to Implement Sewage Works |
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| 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).
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| Regording the main roles and activity of these organization, please |
| refer to following page. |
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| 5. Infrastructure Intensive Development Plan |
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| 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 |
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| Partial amendment of Sewerage Law was made on June 2005, and |
| came into forth in November 2005. |
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| 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 |
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| 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 |
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| 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 |
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| 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 |
| systems. |
| 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 |
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| Sewerage Systems create a useful recourse such as treated |
| wastewater, valuable water resource in urban area and sewage |
| sludge, new biomass energy resource. |
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| Also, upper space of covered Wastewater Treatment Plant and |
| Pumping Station is valuable open space in overcrowded city, and the |
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inside of sewer pipe is now effectively used for Optical Fiber Cable
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| Installation. |
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| 11. Advanced Wastewater Treatment |
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| 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 |
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| 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 |
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| There are two types of sewage (rainwater and wastewater) collection |
| systems, namely, separate sewer system and combined sewer systems. |
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Combined sewer systems (CSS) have only one pipe which conveys
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| both wastewater and stormwater to a local wastewater treatment |
| plant. |
| 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,
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| 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 |
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| 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. |
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Digester gas, one of the useful biomass produced by anaerobic digestion
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| 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 |
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One of the essential roles of Sewerage
Systems is stormwater drainage.
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| Efficient stormwater drainage control is needed to secure citizen's |
| life and property against flooding and contribute to the sound urban |
| development. |
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In Japan, "Development of Safety City for Heavy Rain" is one
of
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| 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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