• Waste management in Japan
  • Circular economy in Japan
  • Waste management in Asia
  • Disaster waste management
*The following is an English translation of an article from the January 2012 issue of the Center's online magazine (see the original text in Japanese).

Overseas Expansion of Japan's Johkasou (Decentralized Domestic Wastewater Treatment System)

January 2012 issue
Yoshitaka EBIE


Johkasou is Japan's original technology for treating domestic wastewater from toilets, kitchen sinks, baths, and so on (see the March 5, 2007 issue: A Small Device to Clean Wastewater Every Day [in Japanese]). It is a decentralized treatment system mainly for individual houses. Since Johkasou can be quickly installed, its development in combination with centralized treatment system called sewerage system can achieve speedy and cost-effective domestic wastewater treatment.

Introduction of effluent treatment technologies to developing countries

The United Nations Millennium Development Goals (MDGs) set forth eight goals for international society to achieve in the 21st Century, which aims at ending poverty and hunger, and ensuring environmental dimensions of sustainable development. The MDGs sanitation target is to halve the population with no access to improved sanitation by 2015. The MDGs define improved sanitation facilities in a very simply manner. Toilets having a pit covered with a slab, having walls for ensuring privacy, and being accessible at any time of a day are recognized as improved sanitation facilities. According to the WHO/UNICEF report of the Joint Monitoring Programme (JMP) for Water Supply and Sanitation, 2.5 billion people, including 1.8 billion people in Asia, had no access to improved sanitation in 2006. Of those people, 1.2 billion have no other choice but to practice open defecation. As I have stumbled across a site of such practice at town rivers during my business trips abroad, I understand that it is only natural for these countries to prioritize improving the situation that majority of their population even do not have access to toilets. However, technology transfer with the aim of solving environmental problems as well as sanitation problems, is required in the long run. Johkasou, one of these technological measures, is expected to largely contribute to solving both.

In the fight to improve sanitation in developing countries, many official development assistance projects have been implemented to date, mostly to establish sewer systems in the most densely populated areas. From 2003 to 2007, a yen loan of about 350 billion yen was provided by Japan to finance 40 sewerage projects in nine countries, which allowed 22.5 million more people to benefit from these sewer systems. On the other hand, for suburban and rural areas, there was only a small increase in the number of projects to introduce domestic wastewater treatment systems. Sewer systems are very cost-effective and work extremely well in densely populated areas. While some economically developed urban areas can sustain these systems into the future, other densely populated areas in poverty are unable to build even latrines, let alone sewer systems. The areas where population growth is expected to continue in the future, including slums in and around large cities, hardly receive adequate support. These areas are reported to be facing the most serious sanitation problems, and therefore, are also facing the highest degree of difficulties in devising appropriate countermeasures against such problems.

Transferring Johkasou technology

Johkasou is Japan's unique technology for wastewater treatment. It is a compact facility that enables advanced wastewater treatment even in a country like Japan with limited land area. Currently, various wastewater treatment technologies are being developed in other countries as well, but Japan's Johkasou has characteristics that stand out from them. In Japan, Johkasou works as a system that involves many processes and expertise. The technicians who install it (Johkasou Installation Workers) and operate it (Johkasou Operators) must have the required national qualifications. In addition, the system's operation needs to be monitored by qualified supervisors (Johkasou Inspectors), and its desludging must be handled by certified technicians (Johkasou Desludging Technicians). These processes and expertise are all integrated into the Johkasou system. No such system exists in other countries.

When introducing Johkasou technology to foreign countries, it is of course necessary to customize the technology to suit their regional characteristics such as the sewer volume per person per day (see related information in the January 2012 issue [in Japanese]), wastewater quality, climate and lifestyles. In addition, for adequately promoting the Johkasou technology, it is also important to operate them as a system as mentioned above. I believe that a social system including Johkasou maintenance and management, collection/transportation of sludge, operation of sludge treatment facilities, and inspection framework is indispensable. Moreover, capacity of the stakeholders needs to be developed comprehensively, for example, in the areas of standardization of knowledge and skills of those who are involved in the system, and enhancement of residents' awareness of environmental issues.

Especially when planning to introduce wastewater treatment facilities, responsible government administrators tend to focus on the population coverage of wastewater treatment system when evaluating these plans. However, sooner or later, a malfunction in the entire system will occur if sludge treatment process is omitted. It is obvious that wastewater treatment generates sludge and residue. So, it is important to consider entire system, including sludge treatment, from the planning stage of the development of a wastewater treatment system. By doing so, they will not have to deal with serious problems in landfill sites such as longer time for waste stabilization, higher strength of leachate water and larger amount of greenhouse gases emissions (mainly methane). For this reason, in planning wastewater treatment facility, evaluation of all the process flows to the final disposal of the sludge and residue is important, not just the population covered.

With regard to raising residents' awareness of environmental issues, steady outreach activities are crucial, among others, in developing countries. Stakeholders can be invited to participate in publication and distribution of newsletters on environment, or introduction of related issues on the internet.

Incentives for installing Johkasou

Advanced treatment of domestic wastewater by Johkasou could not only improve water environment, but also enables various utilization of treated water. Especially, regions with limited water resources have large potential needs for the treated water. Introducing public sewer system to the areas with no piped water supply system may seem to be unrealistic, but people could feel stronger needs for it if they regard the sewer treatment system as a water production device, not just as a treatment device. Particularly, since Johkasou is an onsite facility that operates at the place where water is used, it can be installed near the point of specific water use to achieve specific levels of water quality that suit different water utilization needs. If this aspect of utilization of treated water is incorporated in the evaluation of its development plan, the Johkasou technology may be considered more useful.

Many structural issues as well as maintenance and management problems have been pointed out for septic tanks that are widely used in developing countries. Residents may not see much benefit from installing Johkasou with additional cost if they already have flushing toilets and have installed septic tanks. Still, as noted above, introduction of a package of Johkasou technology to overseas that offers not only sewer systems but also water supply systems for various users, could increase the value of Johkasou. Even those residents who already have installed flushing toilets and septic tanks may be motivated to install Johkasou.

In reality, we may not even have to mention the advantages of such added values. Lack of improved sanitation facilities leads to tremendous economic loss. For example, in Cambodia, Indonesia, Vietnam and the Philippines, its negative economic impact to human health, water resources, outdoor environment, people's daily lives, and the tourist industry is as much as $9 billion (2005) annually, that is equivalent to about 2% of the total GDP of the four countries.

For developing countries to be able to take their own sewer treatment measures autonomously using their own financial resources, it is important to raise these issues to their national or local decision-making bodies and to present these comprehensive long-term economic benefits.


  1. Hashimoto K. (2009) Sanitation Conditions in Asia, Kankyo Gijutsu Kaishi, 134, 11-13
  2. World Bank, Water and Sanitation Program (2008) Economic Impacts of Sanitation in Southeast Asia.