Water Quality Control Department, Wastewater System Division
1. Main Research Field of the Division
ŸSewerage Planning
  Although the national average percent of sewered population has become 76% as the result of intensive investments in few decades, the percent in medium- and small-size municipalities is still low. Sewerage is regarded even in rural areas as a national minimum in Japan.  In order to develop sewerage in the areas, effective and efficient planning is required because rural areas are sparsely populated.
ŸStormwater Control
  Urbanized areas with high population densities and high assets concentrations are still suffering from serious inundation due to stormwater.  Especially, these few years some big cities in Japan were damaged by torrential rain with short duration.  In addition, in combined sewer system mainly adopted by large cities, discharge of untreated sanitary sewage during heavy rainfall threatens water environment in public water bodies.  In this context, comprehensive countermeasures are required for stromwater control.
ŸSewer System
  The sewer system accounts for about 76% of whole sewerage construction cost including collection and treatment system.  Length of existing sewers in Japan is more than 450,000 km thanks to the sewerage development.  Therefore it is increasingly necessary to conduct well-planed renovation and maintenance of sewer system.

2. Major Theme of Research and Development
2.1  Asset Management for Sewers
 In recent years, road cave-ins and similar accidents have been frequently seen. To prevent such accidents, the deterioration in sewers should be accurately detected. Deterioration in sewers is commonly determined in accordance with visual inspection criteria using TV cameras, but these inspection criteria were established mainly for rigid pipes such as reinforced concrete pipes. It is, therefore, difficult to detect deterioration with the conventional criteria for PVC pipes, which are plastic flexible pipes and account for about 50% of the total length of pipe in the country. Considering such circumstances, NILIM has established visual inspection criteria (draft) for detecting deterioration in PVC pipes.
 Accordingly, NILIM collected and analyzed TV camera survey data from local governments in order to identify the deterioration characteristics unique to PVC pipes and create visual inspection criteria for deterioration, and conducted TV camera surveys of PVC pipes laid more than 30 years ago, and load-proof performance tests and two-dimensional nonlinear static analyses (CAE) of deteriorated PVC pipes.
 Consequently, as deterioration characteristics of PVC pipe, the presence of overall section change and local section change, and the relationship between cracking and load bearing capacity were clarified.  Based on these findings, we added the flatness and deformation of PVC pipes to visual inspection criteria and clearly positioned the inspection criteria for cracks.

2.2 Research about countermeasures for sewage system against large-scale earthquake
  When sewage systems are damaged by earthquake, the damages affect public health and social activities such as disorder of sanitation facilities and traffic disturbances.
  In this research, we collect information of past cases of damaged sewage systems, and construct the database system. When we construct the database system, we try to choose appropriate indexes for damaged factor of sewer pipes. After we finish constructing the database system, we are plan to publish the system and would like to contribute for the damage prediction by a large-scale earthquake.
And the economical loss is extracted based on sewer damage prediction. Then how to determine the priority of earthquake countermeasures of sewage systems will be proposed.

2.3 Research on Promotion of Efficient Countermeasures for Urban Stormwater
  In recent years, concentrated heavy rain have occured frequently in many regions of Japan.
 As the frequency of heavy rains is increasing, concern is also increasing over the decline in stormwater penetration due to the progress of urbanization, as well as the increase in inundation damage potential due to the development of underground space use.
 For the purpose of the inundation damage reduction in the city, we study effective inundation countermeasures planning technique and utilization method of real-time rainfall data by XRAIN

2.4 Demonstration Study of Breakthrough by Dynamic Approach in Sewage High Technology Project (B-DASH Project)
  Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has started Breakthrough by Dynamic Approach in Sewage High Technology Project (B-DASH Project) since 2011, and The National Institute for Land and Infrastructure Management (NILIM)  has been an implementing agency for the demonstration study.
 The purposes are achieving cost reduction and creation of renewable energy in sewerage work through the demonstration and widespread use of excellent innovative technology.
In order to improve the inundation prevention features in the city, we have done the demonstration study by the integrated system that the individual technologies on the analysis and measurement of rainfall and water level utilizing ICT.

2.5  Research on low cost sewer installation technology
 In Japan, sewer service accessibility rate reached to 76% in 2013. The remaining unsewered municipalities are less populated. Consequently, installation cost per household goes up.  In addition, Japanese population is on the decrease. Current unsewered municipalities are likely to lose their population further. However, as basic human needs, sewer service has to be provided for everyone. Under this situation, MLIT started experimental works project to lower the cost of sewer. The project considers sub-standard technologies that cannot be taken nationwide.

3. Research staff

Head Iwasaki H.
Senior Researcher Fukatani W.
Senior Researcher Matsuura T.
Researcher Hiraide R.
Researcher Kawashima H.
Research Engineer Nakamura Y.
Guest Research Engineer Kondoh H.
Guest Research Engineer Noda Y.
Secretray Yabuta Y.



NILIM National Institute for Land and Infrastructure Management
Ministry of Land, Infrastructure, Transport and Tourism

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