Japan’s Experiencein
Decentralized Sanitation (Johkasou)
Xinbi Yang
Japan Education Center of Environmental Sanitation

Aizawl, INDIA
28 Feb. 20121

Night Soil and Domestic Wastewater Treatment Systemsin Japan

2

Population Served by Different Systems

14%

Sewerage system
Rural sewerage system
Johkasou system
Night soil treatment

9%
74%

3%

(as of the end of FY 2009)10090(as of the end of FY 2009)

99.4

90.3

88.9

84.5

80

Perrcentage, %70

78.0
71 071.0

S off major
Sumj domesticdti wastewatert t ttreatment
tt systems
t60
50403020100.5

5.9

7.5

9.6

500-1,000

300-500

100-300

16.9

13.9

Johkasou system

0More than
1,000

50-100Less than 50

Size of municipalities, thousand people3Number of Installed Johkasou
Johkasou：2.9 million units
Tandoku-shori johkasou：5.45 million units(as of the end of FY 2009)

65.3%
34.7%

A small-scale johkasou
4Advantages
Adt
off JJohkasou
hkSystem
S tforf
Decentralized Treatment
 Low initial investment cost
 Little topographic limitation, short installation time and early
realization of the effects
 Invaluable contribution to maintaining sufficient water in small
rivers and aquatic environments near inhabited areas
 Johkasou-treated water and sludge are easy to reuse Less vulnerable to earthquakes and other disasters

5Pollutant Loads for Johkasou DesignDetermination of Johkasou Size in Buildings Classified
by Purpose of Use (Examples)
JIS A 3302 2000

Structure and Treatment Performance of Johkasou

Treatment Principles of Johkasou

9A smallsmall-scale
scale Johkasou (FRP)

Diffusion pipe

Effluent water quality
BOD <=20 mg/l

Influent

Anaerobic
filter tankSeparated
sludgeContact
aerationtank

Sedimentation
tank

DisinfectiontankEffluent

Sludge10Filter Media Used in Johkasou

A Johkasou for BOD&N Removal
Pipe for recirculationpIntermittent ppump

DisinfectiontankAnaerobic filter tank
(1st room)

Effluent water quality
Anaerobic filter tank
( d room))(2ndBOD <=20 mg/l
T‐N <=20 mg/l

Contact Aeration
Diffusing pipetankrecirculation

Influent

Anaerobic
filter tankContact
aeration tankFlow equalization

Sedimentation
tank

Sedimentation
tank

DisinfectiontankEffluent

Sludge12

A Johkasou
J hkforf BOD&N&P R
RemovallCell base
リン除去装置Cell＜槽外設置＞
base
Cellbase【防水コンセント】

C t lControler【制御ボ クス】【制御ボックス】

Cell【電源ケーブル】
base

C槽
Cellll bbase＜槽内設置＞【中継ボ クス】【中継ボックス】

Relay box
防水コネクタConnecters

Cellbase【セル】

固定Bolts

Cellbase
セルベース

ボルト
鉄電極
Electrodes

Effluent water quality
BOD <=10 mg/l
T‐N <=10 mg/l
T‐P <= 1 mg/l
13

A Membrane Johkasou

Effluent water quality
BOD <= 5 mg/l
T‐N <=10 mg/l
14

Johkasou classified by the treatment capacity• Small-scale jjohkasou: for 5 to 50 NUD , or the averagegamount of wastewater less than 10 m3/day.
• Medium-scale johkasou: for 51 to 500 NUD, or the averageamount of wastewater less than 100 m3/day.
• Large-scale johkasou: for 501 NUD or more, or theaverage amount of wastewater more than 100 m3/day.
/day
NUD: number of user for design

IInstallation,
t ll tiO&M andd Desludging
D l d ioffJohkasou system

Installation
Operation＆Maintenance

Desludging
16

Legislative Infrastructure Underpinning
Johkasou Systems17

Operation,Oti
MaintenanceM i tanddInspection of Johkasou

Framework of johkasou management under the Johkasou Law
18

Construction ofJohkasou

19

Details of Operation, Maintenance andIInspectiontioff Johkasou
J hk20Johkasou Technicians and Vendors(As of the end of FY 2007)21

S b id Programs
Subsidy
Pfor
f JJohkasou
hkInstallation
I t ll ti

22•Johkasou has economical advantages and is effective fordecentralized sanitation in areas of low population density.
•Johkasou is a system including hardware (treatment plants)

and software (O&M,(O&M inspection under a legal framework) .
The latter issues is much more important in decentralizedsanitation.
•The experience of Japan in decentralized sanitation withjjohkasou
is useful and applicablepp
to other countries as aprevalent measure of sanitation.