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FY 2011 Dissemination Status of Johkasou, On-Site Treatment Systems for Domestic Wastewater

August 31, 2012

The dissemination status of johkasou, on-site treatment systems for domestic wastewater
The number of people using johkasou is 10.79 million and the dissemination ratio is 8.75%.
As of the end of FY 2011, some of the municipalities stricken by the Great East Japan Earthquake (March 11, 2011) are non-survey. Therefore Iwate and Fukushima prefecture are not included in these figures.

Features of Johkasou
Johkasou are on-site treatment systems for domestic wastewater that includes human wastes and are installed at the household level. Treated water is discharged to the nearest public water area. A johkasou has the following features.

(i) Treatment capabilities are the same as those of a wastewater treatment facility in the sewage system.
The removal rate of biological oxygen demand (BOD) is 90% or more.
The BOD of treated water is less than 20mg/L.
(ii) The installation expense is approximately 840,000 yen for a system for five persons, which is comparatively low.
(iii) The duration of installation is one week to ten days, which means investment efficiency becomes apparent at an early stage.
(iv) The system is easy to install, regardless of the geological formation.
(v) The system is basically designed to treat domestic wastewater at each household site. It secures river water volume and contributes to preservation of the water environment, which maintains a diverse ecosystem.
(vi) The system utilizes the natural purification capacity of small rivers

Promotion of Johkasou Installation
The Ministry of the Environment (MOE) established the Johkasou Promotion Program in FY 1987. In this program, the MOE provides subsidies to the local municipalities that are subsidizing the installation expenses of citizens who will install Johkasou.
The MOE also developed the Municipal Johkasou Promotion Program, in which local municipalities install and maintain johkasou themselves in 1994. The MOE has been promoting this program because steady maintenance of johkasou is ensured by municipalities through this program. In the supplementary budget of FY 2002, the area for subsidies was expanded to those in which improvement of johkasou is more economic and efficient compared with collective wastewater treatment systems, including sewage. The number of municipalities carrying out the program is 290 in FY 2012. The MOE will further promote this program.

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