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Press Release

Dissemination Status of Johkasoh, On-site Treatment Systems for Domestic Wastewater

August 22, 2003

1.   Dissemination Status of Johkasoh

The Ministry of the Environment (hereinafter referred to as the "MoE"), the Ministry of Agriculture, Forestry and Fisheries and the Ministry of Land, Transportation and Infrastructure have, since 1996, jointly released the dissemination status of wastewater treatment facilities (taken here to include johkasoh and community wastewater treatment plants, rural sewage systems and general sewage systems) managed separately by the three ministries. The number of people utilizing these wastewater treatment facilities is now 95.99 million(Table.1), representing 75.8% of the total population (referred to hereinafter as the "dissemination ratio"). The total number of people using Johkasoh stands at 9.93 million, giving it a dissemination ratio of 7.8%(Table.2,Fig.1).

2.   Features of Johkasoh

Johkasoh, which as a general rule treat domestic effluents (human waste and wastewater from household) at each household, releasing treated water into nearby public water area. The features of the system are as follows:
(1) Treatment capability is equivalent to that of wastewater treatment facilities of public sewage systems.
  • Removal rate of biological oxygen demand (BOD) is 90% or more.
  • Final BOD of treated water is less than 20 mg/l.
(2) Installation expense is approximately 900,000 yen for a system for five persons, which is comparatively low.
(3) Time required for installation is one week to ten days, which means the advantageous results of the investment becomes apparent at an early stage.
(4) The system is easy to install regardless of the local geological features.
(5) The system utilizes the natural purification capacity of small rivers and contributes to their maintaining of an appropriate water volume.

3.   Promotion of Installation of Johkasoh

The MoE established the Johkasoh Promotion Program in FY1987. Under this program, the MoE provides subsidies to local municipalities which are subsidizing installation expenses of citizens installing a johkasoh. The MoE has also created the Municipal Johkasoh Promotion Program, in which local municipalities themselves install and maintain the johkasoh. The MoE has been promoting this program since regular maintenance of the johkasoh is ensured by municipalities through this program. In the supplementary budget of FY2002, the areas eligible for subsidies were expanded to those in which improvement of johkasoh is more economic and efficient than collective wastewater treatment systems, including sewage systems. Areas subject to the fifth area-wide total pollutant load control were added to the areas eligible for subsidies and the restrictions regarding the number of houses in lesser-populated areas and on isolated island were loosened starting with the FY2003 budget. The number of municipalities carrying out the program has increased from 120 municipalities as of January 2003 to 163 as of April FY2003. The MoE will continue to promote this project in the future.

* Table.1 Number of People Served with Wastewater Treatment Facilities by Type
* Table.2 Population Using Johkasoh and Dissemination Rate
* Fig.1 Dissemination rate of johkasoh in cities classified by population

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