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International Workshop on Decentralized Domestic Wastewater Treatment in Asia

Water Reuse from Decentralized 

Domestic Wastewater Treatment Facilities

Date: 28th November, 2023

Time: 15:00~18:30 (Japan standard time)

Venue: Webinar via Zoom 

Language: English / Japanese (simultaneous interpretation)

Organizer: Ministry of the Environment, Government of Japan (MOEJ)


Water Reuse from Decentralized Domestic Wastewater Treatment Facilities

Due to the impacts of climate change, droughts and water shortages are severe and increasing problems affecting the global socio-economic development. Accordingly, the demand for water reuse, including the treated effluent from decentralized domestic wastewater treatment facilities, is increasing.
If the Johkasou can prove its availability of effluent in addition to the appropriate domestic wastewater (both black water and gray water) treatment performance, Johkasou would captivate the international market of the decentralized wastewater treatment facility. Thus, research activities on reuse of the effluent from the Johkasou is highly expected to provide the detail information. However, In Japan, because the necessity for reuse of effluent from the Johkasou is little since the daily life is rarely suffered from water shortage, and since the Johkasou has been developed in the context of night soil treatment originally, research work or investigation on reuse the effluent from Johkasou is not sufficient. For this reason, Japanese side are primary expected to realize the international situation how much demand for the wastewater effluent reuse and to discuss how Johkasou can approach to improve this situation.
In this Workshop, as a Keynote, international organization, World Bank will introduce why the effluent reuse is important through the aspect of the circular economy, how much demand there is for the effluent reuse of wastewater treatment facilities, and what examples of efforts are being made around the world.
Following, in Session A, will introduce examples of effluent reuse from decentralized wastewater treatment facilities in Japan and overseas.
Johkasou can discharge better water quality of effluent than decentralized wastewater treatment facilities such as septic tanks, which are commonly used in developing countries. Therefore, it is assumed that the treated water can be used more easily and stably than septic tanks.
The good quality of effluent from the Johkasou is achieved not only by proper design and manufacturing that enable to treat both black water and gray water, it is brought by as well as appropriate construction, maintenance, cleaning, and inspections guaranteed by the Johkasou Act. In other words, the reliable functioning of legal systems related to decentralized wastewater management, such as Johkasou Act, can be considered to increase the utilization potential of effluent reuse.
Therefore, in Session B, an official from the Johkasou Promotion Office of Ministry of the Environment Government of Japan will introduce the Johkasou Act, and as well as an ordinance on decentralized wastewater management currently being under consideration in Telangana, India. This ordinance has innovative contents requiring effluent reuse in addition to install the decentralized wastewater treatment facilities for the buildings above a certain scale.
This workshop will discuss the importance of effectively reusing the treated effluent of decentralized domestic wastewater treatment facilities, as well as the legal and regulatory framework needed to create the environment enabling the scaling up the use of decentralized domestic wastewater management in order to achieve water reuse more widely. In this workshop, the participants are expected to debate actively and exchange their experiences, opinions, and points of views.

Speakers & Material Download


Water in Circular Economy and Resilience (WICER)

Ms. Midori Makino

Lead Water Supply and Sanitation Specialist, World Bank

From the perspective of the circular economy (CE) in the water sector based on the international trends and case studies, will share about why water recycling is important, what kind of profit returns to the region.

A-1 (2126KB)

Overseas case study: Reuse of the effluent from Johkasou

Mr. Rio Waza


In India, in addition to the impact of climate change, the water supply infrastructure is inadequate due to rapid urban expansion, and there is a large demand for the effluent reuse from wastewater treatment plants.
In this presentation, will introduce a good practice of the effluent reuse of Johkasou installed in India, the feedback from the users, and the demand for treated water in India.

A-2 (3259KB)

Recycling of treated water by Johkasou

Mr. Shigeyuki Hikotani

General Manager, Special Equipment Department,Kansai Airports

At Kansai International Airport, Japan's largest (38,500 people at present, 77,000 people in the future) Johkasou (activated sludge circulation nitrification and denitrification method, coagulation sedimentation method, rapid sand filtration method) is installed, and more than 60% of the effluent is reused as recycled water in airport facilities. He will talk about the benefits, challenges, and future perspectives of using effluent in facilities. Also, will introduce B/C when using tap water and when reusing effluent.


Social implementation research on cultivation of rice suitable for sake brewing by effluent from large scale Johkasou -Eco-friendly sake “Sui Shigen” is newly released!

Dr. Shuhei Masuda

Associate Professor, Department Civil Engineering and Architecture, National Institute of Technology, Akita College

In Akita Prefecture Japan, there is a case that Sake-rice is cultivated by effluent from the Rural sewerage system (large scale Johkasou, with anaerobic filter bed, contact aeration treatment), and brewing sake with the cooperation of a local sake brewery. will talk about the benefits, challenges, and future perspectives on effectively utilizing the effluent which contains fertilizer components such as nitrogen and phosphorus in the agricultural field.


Advanced treatment of domestic wastewater using a combination of Johkasou and simple BGF - Examination of production and safety of vegetables and fruits -

Dr. Yasuo Ozaki

Professor Emeritus, Akita Prefectural University

Effluent from a small scale Johkasou (5 PE) is stored in a tank, and vegetables and flowers are cultivated using a biogeofilter. In this presentation, will focus on challenges when using effluent from small scale Johkasou for crop cultivation and the prospects to spread this system.


Mechanisms of Johkasou Act

Mr. Ryoma Sato

Section Chief, Office for Promotion of Johkasou, Waste Management Division, Environmental Regeneration and Material Cycles Bureau, MOEJ

In this presentation, will introduce Japanese laws and regulations related to the decentralized wastewater management, especially focusing on the Johkasou Act, which contributes to maintaining good water quality of effluent from Johkasou.


Onsite Wastewater Treatment and Recycling Regulations –2023 –Draft

Prof. Srinivas Chary Vedala

Professor and Director, Administrative Staff College of India (ASCI) 

Hyderabad City, Telangana State, India, which is suffering from serious water shortages, is formulating an ordinance for decentralized wastewater management and expanded use of recycled water. In this presentation, will introduce the circumstances leading up to the formulation of this ordinance and the similarities with the Johkasou Act.

Introduction of the Moderator

Dr. Pierre Flamand
Manager - international Affairs, Japan Sanitation Consortium (JSC)

Pierre is the Manager of International Affairs at the Japan Sanitation Consortium (JSC). He has over 18 years of experience in sanitation, with particular focus on fecal sludge management. Since joining JSC in 2009, he has been involved in sanitation projects in Viet Nam , Malaysia and Bhutan. He is the co-author of 'Sanitation and Sustainable Development in Japan' (ADB 2016) and 'Accountability Mechanisms for Inclusive City-Level Public Services in Asia' (ADBI 2023). Since 2015, he has been involved in several Working Groups of ISO/TC 224 as an expert representing Japan for the development of international standards. He has in-depth knowledge on how the country has solved the severe sanitation issues in the 1960s, including the role played by the government in the enactment of policies, guidelines, and legal instruments for wastewater management. Pierre holds a doctoral degree in regional development studies and is also a visiting researcher at Toyo University in Japan.

Secretariat Contact

We look forward to receiving your participation. 
If you have any queries, questions, or suggestions, please contact the Secretariat of this Workshop, below.

Yurie Shirakawa
Senior Researcher, JECES
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