8th International Workshop on Decentralized Wastewater Treatment in Asia
21st January, 2021

Situation of wastewater management
disasters Inspection
Desludgingunder
Operation

Desludging

Operation

Inspection

Kikuya Shibata
Secretary General of Miyagi Prefectural Authority for Living Environment

１. Tsunami traces when the Great East Japan Earthquake(Former Kitakami River mouth, Ishinomaki City, Miyagi Prefecture)
Damaged vehicle collection area

Temporary storage area of debris

19. April. 2011
スライド２

２. Situation of damaged sewer system
Treatment facility

Immediately afterthe disaster2nd May, 2011

Shut down4618Damaged

63

44

unknown

11It took about
2 to 348 years to fully
10 recover.

Total

120

120

Pump facility

Immediately after
the disaster2 May 2011

Shut down

78

41

Damaged30

31

Normal operation

Normal operation

Source : MLIT

36

unknown

1

1

Total

109

109
スライド３

３. Johkasou is more earthquake-resilient－Outcome from the previous damage
situation survey on Johksou－〇2011 Emergency investigation of damage to septic tanks after the Great
East Japan Earthquake （April 2012）－Survey results of ３ prefectures(Iwate・Miyagi・Fukushia)
Number of Emergency completelysurveysrepair
destroyed
1,099
24.6%
3.8%

Survey target
All facilities
Tsunami inundation area

278

52.9%

2.5%

outside of Tsunami inundation area

821

14.9%

4.3%

※ Facilities where houses were washed away were excluded from the survey〇Results of past "Large-scale earthquake damage survey" by the Johkasou
function guarantee system
Month,Year

epicenter

Off Miyagi Prefecture
Magnitude 7.1
Tokachi region
9, 2003
Magnitude 8.0
Niigata Prefecture
10, 2004
Magnitude 6.8
Noto Peninsula
3, 2007
Magnitude 6.9
Niigata Prefecture
7, 2007
Magnitude 6.8
Miyagi/ Iwate Prefecture
6, 2008
Magnitude 7.2
Kumamoto Prefecture
4, 2016
Magnitude 6.55, 2003

Number of
Number of
Damageddamagedsurveysratio
Johkasou
1,034

50.5%

615

112.0%

1,428

51

3.6%

971

39

4.0%

1,393

60

4.3%

2,626

140.5%

12,429299

2.4%

Investigator
Miyagi Prefectural Authority for
Living Environment Secretary
Hokkaido Joukasou Association
Niigata Johkasou Seibi Association
Ishikawa Johkasou Association
Niigata Johkasou Seibi Association

 In the sewerage system, thepipes are connected by "lines"
like a mesh, while theJohkasou is resistant toground displacement because
it exists at "points"(advantages of decentalized
system, Johkasou).
 The impact on Johkasou islocal and limited, and even if
there is a total loss, recovery
within a few weeks after thestart of recovery is a great
advantage when considering
the lives of those affected by
the disaster.

Miyagi Prefectural Authority forLiving Environment Secretary
Kumamoto Johkasou Association

スライ４

４. What happened to the Johkasou?－From the damage situationー
４.１ Cases of Johkasou damage caused by an earthquake
Subsidence due to soilliquefaction

Poor inflow gradient

Pic ２

Pic１
Damaged inflow connection

Damage to the upper side of
the tank

Pic ５

Pic ４
Deformation of the upper part of
the tank, air piping, and transferpipe

Deformation of
the upper part of the tank
Pic ８

⇒ No abnormality in the main
body (reusable)

Body floating

Deformation of partition plate

Pic 4

Pic ９

Pic ３
Inflow port during provisional use

Crack occurrence

Pic ６

Damaged flange surface

Pic ７

Dropout od baffle

Outflow of moving bed

Pic１０

Pic １１スライド５

４.２ Classification of damage for Johkasou caused by an earthquake（Classified by the presence or absence of liquefaction）
loosing airpipe union
No
SoilLiquefaction

No
Body Floating

Level 1

Level 2dropping baffle/disinfection tube

deformation on the bodyNo
Body Floating
Soil
Liquefaction

Level 4 , 5

Body Floating

Level 2

Level 3
crack occurrence on the body
Level 3
hard damage on the bodyno damage on the body
damage/deformationon the body

Level 4deformation/damageon the partition

Level 2

outflow of moving bed/ Level 2
contact media
deformation/damageon the air pipe

Level 2Frequency of damage
FrequentlySometimes
rarelyLevel 5

Level 0poor gradient on the connection
Level 1
damage on the connection

damage on the air pipe
connection
Subsidence ofBackfill part

Level 1

Level 1trouble on the slab/raisingdeformation/damage Level 1on the body(upper side )スライド６

４.３ Estimation of damage to the Johkasou based on theprevious large-scale earthquakes
Damage estimation of Johkasou

Seismicintensity
Over lower 6

Upper 5

Plate boundary type earthquake (M7)

WholeWhole••••

Direct type earthquake (M6)

Body
Inflow/discharge(pit) pipe
Air pipe
Other featuresExpansionofdamage

•
••

Body
Inflow/discharge(pit) pipe
Air pipe
Expansionofdamage

A part ofLower 5•••

Body
Inflow/discharge(pit) pipe
Air pipe

A part of•••

4Damageestimated range

Wide range

Body
Inflow/discharge(pit) pipe
Air pipe
Around the epicenter area

※ If the magnitude (M) increases 1, the energy of the seismic wave will increase by
about 30 times, and if it increases 2, it will increase by about 1,000 times.
スライド７

４.４ Future of Johkasou construction(disaster prevention / mitigation)
The three points of Johkasou damage that can be seen from the case of theGreat East Japan Earthquake① The Johkasou with support post, there is almost no surfacing due to liquefaction.
② Most of the surfacing of the body is due to the liquefaction of the backfilled part.
③ Floating prevention metal fittings are intended for static groundwater and are notsupposed soil liquefaction around the Johkasou.
Prevention method on Soilliquefaction of sewer

Concept of disaster mitigation measures
Preventing soil liquefaction of backfill part is the "basic
consept of an earthquake-resistant Johkasou."Eliminate one of the following three factors which lead soil liquefaction.
① The ground water level in the backfill area is high.
② The grain size distribution of soil used for backfill area is easily liquefied.
③ Low degree of sand compaction of backfill area.

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４.５ Classification of damage for Johkasou
caused by tsunami (flood)and damaged case of Johkasou

2nd damage

Tsunami/ flood damage

When the inundation
depth is shallow

Blower outflow/flooding• There is a high possibility of electric leakage

Pic １Flooded above floorlevel(below than 2m)

Inflow of sediment/sludge• Inflow of seawater• Abnormality in bubbling / transfer• Inflow of oil• Collapse of disinfection cylinder

When the inundation
depth is deep

Manhole outflow• Large inflow of rubble, sediment, etc.
• Collapse of disinfection cylinder• If the inundation depth is shallow, themanhole can be locked to prevent outflow.

Inundation on thesecond floor or more(higher than 2m)
The damage to thebuilding is also
enormous

When removing
debris, etc.

Inflow ofsediment/sludge

Erosion of surrounding ground/SlabPic ２outflow

damage tothe body

Erosion of surrounding ground/Slab outflow• Exposure of the body and piping• Damage to the body（Since the main body is underground, thedamage is less than that of the building.）
Significant damage to the body• Most of the damage to the main body is dueto heavy machinery such as backhoe.
(A mark is required when using the Johkasou
continuously)

Pic ３
Damage causedby heavy
machinery

Frequency of damage
Frequently
Sometimes
rarely

Pic ４

スライド９

４.６ Judgment of availability of provisional use
In the case of the Great East Japan Earthquake, it is difficult tojudge whether “Available" or not without sufficient experience,
except for a clear situation of floating and an abnormal low waterlevel in the Johkasou immediately after the earthquake. Therefore,
it has been judged just "provisional use is possible" or "nonavailable". However, as conditions for "provisional use is possible",
it is necessary to satisfy the following conditions.
① The inflow water and the water in the tank are not leaking oroverflowing.
② Disinfection process is certainly done.

Under those conditions, even if the blower is stopped due to apower failure, electric leakage, damage, etc., provisional use ispossible by performing simple processing.
As stated in the manual provided by Ministry of the Environment,
the period of provisional usage is about 3 months at the maximum,and during this period the restoration work shall be completed.

スライド１０５. Johkasou installed at temporary housing
５.１ Situation
 In the Great East Japan Earthquake, Johkasou can be restored and installed more
quickly compared with sewers or rural sewerage system which take a long time torecover, therefore Johkasou have been widely adopted in temporary housing andtemporary stores.
Approximately 1,700 units were installed in Iwate, Miyagi, and Fukushima prefectures.
 In the mountainous area or area with many small scale colonies, installation ofJohkasou in such temporary housing seems the most effective (financially and timely)
development procedure.
 However, since it was necessary to construct a huge number of Johkasou along withtemporary housing in a very short term, many of the Johkasou had been installed on
the ground (not underground), and there were problems in terms of maintenanceworks and its system.
 In addition, it was an urgent move-in in a disaster, there was a problem which a large
inflow of fats & oils and impurities, therefore, it was necessary to explain to theresidents how to use the Johkasou installed at the temporary housings.
improvement approach for maintenance(sign boards and numbering)

No scaffolding for maintenanceNo heat retention measures
No scaffolding for
maintenanceNo heat retention
measures

Inadequate screen equipment

Difficult toattach / detachthe pump

No screen

スライド１１

５. ２ Installation example of Johkasou at temporary housing

Pic １

Pic ２

Fukushima Prefecture(Semi-underground installation＋embankment：
45 EP×2 units)

Iwate Prefecture(underground ：35 PE)

Pic ３

Iwate Prefecture(Semi-underground installation、heat retention measures：42 PE)

Pic ４

Iwate Prefecture(Ground installation、No heat retention measures：
スライド１２90 PE×6 units＋30 PE)

６. Status of Johkasou installed in evacuation shelters(Source: (2016) Damage situation survey on Johkasou by Kumamoto earthquake,
Association of Johkasou, kumamoto.)

In Minamiaso village (Kumamoto earthquake: 14th April, 2016)① Kukino General Welfare Center
The total number of evacuees were 3,370 peoples until 18th May. There were several days when themaximum number of evacuees exceeded the PE of Johkasou (287 PE) , however, there were no problems
with the treatment function of the Johkasou, and the treated water quality was stable.
treatment processPE

contact aerationsystem

287

item
11, Apr 18, Apr 22, Apr 20, May 27, May※all evacuees
Number of evacuees
670
1,471
3,370 ※
pH
7.1
7.8
7.3
7.7 moved out byWater DO
3.8
4.2
3.3
7.7 May 18quality Transparency
100100100100
item
Residual chlorine
0.20.20.20.2Chlorine amount
1,000
1,000
1,000
1,000
1,000

② Minamiaso Junior High School Gymnasium
The total number of evacuees were 13,072 peoples until 24th May. On 14th April, a power outage of thedischarge pump and damage (displacement) on the inflow pipes were monitored, however, by 19th April
restoration works such as emergency generator installation has taken. There were 800 evacuees atmaximum in the term, and it greatly exceeded the PE of Johkasou (66 PE), however, there were noproblems with the treatment function and the treated water quality was stable.
treatment process

PE

item
14, Apr 18, Apr 25, Apr 18, May 17, Jun 13, Jul
Number of evacuees
2,000
5,522 12,292 13,072 ※moving bed
pH
8.3
8.0
8.1
7.7
7.6
aeration system
Water DO
4.2
4.8
4.4
4.0
4.5
66
with flow control
quality Transparency
3030
30
3030tank
item Residual chlorine
0.2
0.2
0.2
0.2
0.2
Chlorine amount※ all evacuees moved out by 24th May
スライド１３

７. 2011.3.11 “Records and experiences ofthe Great East Japan Earthquake”
You can download “Records andexperiences of the Great East Japan
Earthquake” from the URL below.
http://www.m-seikatsukankyo.or.jp/
other/report311/

Thank you for your attention.
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