Domestic Wastewater Treatment
by Johkasou Systems in Japan
Hiroshi Ogawa
Japan Education Center of Environmental Sanitation
2-23-3 Kikukawa, Sumida-ku, Tokyo 130-0024, Japan
What is Johkasou?
① Blower
② Air pipe
③ Inflow pipe
④ Wastewater pit
⑤ Johkasou
(building frame)
⑥ Disinfection chamber
⑦ Outflow pipe (effluent)
An Example of Johkasou Installed at
Individual House
A small-scale Johkasou (FRP)
Effluent water quality
BOD ≦20 mg/l
Influent
Anaerobic
filter tank
Contact
aeration tank
Separated sludge
Sedimentation
tank
Sludge
Disinfection
tank
Effluent
A Middle-scale Johkasou (FRP)
Inflow pipe
Sludge thickening-storage tank
Contact aeration tank (2nd room)
Outflow pump tank
Outflow pipe
Flow equalization
tank
Contact aeration tank (1st room)
Disinfection tank
Sedimentation tank
Middle-scale johkasou
A Middle-scale Johkasou (RC)
Main Systems for Domestic Wastewater Treatment
Johkasou
Rural Sewerage
Public Sewerage
Various Systems for Treatment of Night Soil, Sewage and Wastewater in Japan
(Storage tank)
Night soil
Separate sewer system
Domestic
wastewater
Night soil treatment
facility1
Tandoku-shori
johkasou2
Combined sewer system
Sewerage system
Johkasou4
Night soil + Gray water3
Rural sewerage
system
Community plant
Storm
wastewater
(Urban storm drainage system)
Note: 1. Night soil treatment facilities also treat sludge collected from tandoku-shori johkasous,
community plants, gappei-shori johkasous and sewerage system in rural area.
2. The many are installed in individual houses.
3. Gray water is miscellaneous domestic wastewater except night soil.
4. Though not many facilities are installed in individual houses, the number is increasing.
Public
water
bodies
Trends of Populations Served by Johkasou, etc.
130
120
Total population
110
100
Population of flush toilets use
Population, milion
90
80
70
60
Population served by sewerage system
50
40
30
Population of johkasou use
20
10
0
1965
1970
1975
1980
1985
1990
Fiscal Year
1995
2000
2005
2010
Advantages of Johkasou System
Flush toilets can be used in unsewered districts.
Miscellaneous domestic wastewater can be treated, contributing to
prevention of water pollution.
Conserving water in small rivers, a human-closely water environment will
be formed.
A small-scale johkasou can be installed at a low cost and in short time.
Wastewater collection and johkasou installation receive less influence of
topographic conditions at the site.
Treated water can easily be reused for various purposes as a reliable
water resource.
Sludge from johkasous can be used as fertilizer or for biomass production.
Johkasous have high resistance against earthquake and other disasters.
BOD Loading per capita per day
of Domestic Wastewater from Household
Cleaning
Night soil
Cooking
BOD loading
43g/cap･ｄ
Gray water
Bathing
Cooking
Cleaning etc.
Washing/Bathing
Flush toilet
40L
72L
50L
38L
Wastewater amount (200L/cap･day)
Legal Systems of Johkasou Systems
（Johkasou Law）
Administrative Agencies
Submission
Recommendation
Governor
Or Mayor
Specified
administrative
agency
Order of
modification
Or rejection
Johkasou Manager
Document
inspection for
installation
Construction
Specified
inspection
agency
Legal examination
after installation
Administrative Agencies
Application
Manufacturer
Approval of type and model
Construction
company
Johkasou
installation worker
Designation
Minister of the
Environment or
Governor
Related Personnel
Agency for the
examination
Agency for the
training courses
Johkasou operator
Minister of Land,
Infrastructure and
Transport
Application
Governor
Registration
Qualification
Designation
Designation
Qualification
Minister of Land,
Infrastructure and
Transport
Minister of Land,
Infrastructure and
Transport
Minister of the
Environment
Minister of the
Environment
Application
Specified
inspection
agency
Operation and
maintenance
Maintenance
vendor
Desludging
Desludging
vendor
Annual legal
examination
Registration
Application
Approval
Governor
or Mayor
Municipal
Mayor
Johkasou Technicians and Vendors on
Johkasou Business
Classification
Number of person/vendor
Johkasou operator
63,104
Johkasou installation worker
77,728
Johkasou inspector
2,533
Johkasou desludging technician
14,205
Vendor for johkasou O&M
9,087
Vendor for johkasou desludging
4,806
Specified examination agency
65
Johkasou manufacturer
38
(By the end of Mar. 2005)
Reuse of Effluent and Sludge
Effluent can be used for:
*Flushing toilet
*Watering
*Car washing
*Firefighting
Domestic
Wastewater
Johkasou
Sludge
Sludge can be for Compost
Effluent
Storage Tank
Effluent
Comparison of Different Subsidy Programs
(For installing a johkasou of 5 NUD, which will cost ¥860,000 if it is not subsidized)
In the case of Johkasou Installation Promotion Program:
Amount subsidized by
municipalities and the
government(￥340,000)
Amount borne by the house owner
(￥520,000)
In the case of Johkasou Installation Program in Specified Areas:
Sewerage works
construction bond
(￥480,000)
Amount subsidized
by government funding
(￥290,000)
Amount borne by
the house
owner(￥90,000)
Toward the Water Quality Protection
in Public Water Bodies and the Creation
of Desirable Water , Reuse of Effluent and
Sludge
The End