go to text

International Workshop on Decentralized Domestic Wastewater Treatment in Asia

MOEJ held the 10th Workshop on 4th November, 2022

The 10th workshop has been held by MOEJ successfully. 
Thank you very much for your participation.
We are pleased to receive your feedback. If you have any queries, questions, or suggestions, please contact the Secretariat of this Workshop, below.

Yurie Shirakawa
Senior Researcher, JECES


Graywater Treatment by the Johkasou and its Social Benefit

Gray water (GW, domestic wastewater except toilet wastewater) is one of the big pollutant sources of water environment as well as Black water (BW, toilet wastewater). In this workshop, we would like to discuss on the Social Benefit derived from GW treatment , taking Johkasou spread in Japan as an example. 

In addition, we would like to focus on what kind of benefit are brought to the public by treating the GW, and what kind of regulations / subsidies are provided by the central / local government to conserve the good water environment (cases from Japan and Vietnam ).


Date: 4th November, 2022

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

Venue: Webinar via Zoom 

Language: English / Japanese (simultaneous interpretation)

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

Introduction of moderators

Dr. Pierre Flamand  
the Manager of International Affairs at the Japan Sanitation Consortium (JSC)

Pierre has over 15 years experience in sanitation, having particularly focused and conducted research on fecal sludge management. 
Since 2015, he has been involved in several Working Groups of ISO/TC 224 as an expert representing Japan for the creation of international standards on stormwater management in urban areas and on-site domestic wastewater systems. 
Pierre holds a doctoral degree in regional development studies and is also a visiting researcher at Toyo University in Japan.

Material download

Keynote(2022-10-30 ・ 3060KB)

Dr. Hiroshi Yamazaki

Professor, Department of Civil and Environmental Engineering, Faculty of Science and Engineering, Toyo University

Based on examples of water quality surveys, etc., and experiences in Japan, Dr. Yamazaki will talk about how much gray water imposes a pollutant load to the water environment.

A-1 (2022-10-30 ・ 3349KB)

Mr. Yasunobu Hamada

Section Manager of Information Processing Division, Inspection Department, Kagoshima Prefecture Environmental Conservation Association

In Aira City, Kagoshima Prefecture, there are districts where the conversion from old type Johkasou (which only treat BW) to Johkasou is progressing without the impact of sewerage facilities nor agricultural sewerage facilities. Mr. Hamada will provide information on how the water quality of the small channel in this district has changed between 2005 and 2022.
In addition, Mr. Hamada will introduce regarding the difference in the appearance and water quality of the surrounding small channel between the old type Johkasou area and the Johkasou area, in Kagoshima Prefecture.

A-2 (2022-10-30 ・ 696KB)

Dr. Masahiro Furuichi

Director of Department of Education and Planning, Japan Education Center of Environment

Based on his published paper, Dr. Furuichi will introduce GHG emission characteristics per volume of treated water and per BOD removed, by comparing Johkasou with other decentralized wastewater treatment facilities such as septic tanks.

B-1 (2022-10-30 ・ 4556KB)

Mr. Masaki Inoue

Senior Manager, Water Environment Division, Department of Environment, Saitama Prefecture

Mr. Takeshi Ishino

Senior Manager, River Environment Division, Department of Land Development, Saitama Prefecture

Regarding the secondary effect of improving water quality in public water body, it would be considered such as improvement of amenities in the living environment, conservation of ecosystems, regional revitalization, etc.

Until now, Saitama prefecture has regarded the "good water environment" as an "asset" and tried to utilize it. , etc.), will also introduce administrative measures such as the river restoration project and the SAITAMA River Supporters Project.

B-2 (2022-10-30 ・ 3484KB)

Ms. Rio Owada

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

Ms. Owada will introduce the background of the Johkasou Act enactment, and the revision of the legal system for treating GW.
And, she will also mention the information on the cost level of the annual operation & maintenance of Johkasou, which is important for the sustainable implementation of domestic wastewater treatment.

B-3 (2022-10-30 ・ 3269KB)

Mr. Norihide Tamoto

JICA Expert of Sewerage Policy Advisor, Ministry of Construction, Vietnam

There is growing international interest (especially in developing countries) in the application of PPP schemes to the sewage treatment sector.
Mr. Tamoto will provide information on the applicability, benefits, and expected challenges in the sewerage sector of the PPP Investment Law that came into force in January 2021 in Vietnam.

Back to TOP