Shinhi Kumokawa Ph.D
Center for International Cooperation of Johkasou System
Japan Education Center of Environmental Sanitation (JECES)

1Device/equipment in johkasou
Primary treatment(1st step)

Sedimentation tank, Anaerobic filter tank, Slit screen, Aerated screen,
Grit chamber,
Bar screen, Flow equalization tank,

Secondarytreatment
2nd step

Contact aeration tank, moving bed tank, aeration tank,

3 rd step

Sedimentation tank

4 th step

Disinfection tank

5 th step

Sludge thickening/storage tank, sludge storage tank,Mechanics

Electromagnetic blower, Control panel, mechanical blower, pump,

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Operations concerning to inspecting, maintaining andrepairing johkasou (Johkasou Act, Article 2-3)

・ Prevent loss of unit function and device breakdown
・ Maintain normal treatment performance
・ Promote proper regular desludging

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Desludging involves extracting the generated sludge and scumfrom johkasou and conditioning sludge in the tank, as well as
cleaning tanks and auxiliary equipment.
(Johkasou Act, Article 2-4)

Recover/reset treatment performance of johkasou

by removing sludge regularly

4o Technical standard for operation and maintenance(Article 2, Ordinance for Enforcement of Johkasou Act)
This standard stipulates maintenance items and adjustment/repair items thatmust be carried out during operation and maintenance for every johkasou andthe auxiliary device.
o Technical standard for desludging (Article 3, Ordinance for Enforcement ofJohkasou Act)
Desludging standards stipulate items to be carried out for each unit andauxiliary device during desludging (e.g. methods for drawing out sludge)
o Guidelines for johkasou operation and maintenance (Official notice)
These guidelines are issued by the Ministry of the Environment as specificpolicies for operations and maintenance technicians. They are designed toensure that operation and maintenance as well as desludging are carriedout optimally and in line with the specific characteristics of each treatment
process.
5Technical standard for johkasou O&M, (1984, Johkasou Act)➢ Guideline for O&M of Tandoku-shori johkasou (2000)➢ Guideline for O&M of small-scale johkasou (1993)➢ Guideline for O&M of medium/large-scale johkasou (2000)➢ Guideline for O&M of N/P removal type johkasou (2000)➢ Guideline for O&M of Membrane johkasou (2000)

Technical standard for johkasou desludging (1984, Johkasou Act)

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1950s

1980s

Tandoku-shori johkasou (treat black water only)

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2010s

Johkasou (treat black + grey water)

(i)(Rule of Using)
Article 1 Rules of using johkasou under the provisions prescribed in Article 3
paragraph 3 of Johkasou Act (hereinafter referred to as "Act") shall be asfollows.
(i) Water amount for flushing toilet shall be appropriate.
(ii) Materials like insecticide, detergent, deodorant, fatty, disposable diaper,
sanitary goods etc. which interfering with the normal functioning of johkasou,shall not be flowed.
(iii) abbr.
(iv) Industrial wastewater, rain water and other special wastewater shall not be
flowed into johkasou.
(v) Johkasou with electric equipment shall not be turned the power supply off.
(vi) The top or around of johkasou shall has no structural object that may
interfere with operation, maintenance and desludging of johkasou.
(vii) The top of johkasou shall not be loaded which may interfere with its normal
functioning.
(viii) The opening part of aerator shall not be blocked.
(ix) When the failure or malfunction is found in the johkasou, it should be
notified to the johkasou manager immediately.

(ii)

(v)

(vi, vii)

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(Article 6-2, Ordinance for Enforcement of Johkasou Act)
Treatment process

Type/size of johkasou

Frequency⚫ Separation-contact aeration process⚫ Anaerobic filter-contact aeration process⚫ Denitrification type anaerobic filtercontact aeration process

1. Johkasou with a size less than 20 PE

4 month

2 . Johkasou with a size more than 21 PE
and less than 50 PE

3 month⚫ Activated sludge process( > 100PE)

1 week⚫ Rotating biological contactor process⚫ Contact aeration process⚫ Trickling filter process

1. Johkasou with sand filter device,

1 weekactivated carbon adsorption device
or flocculation tank ( > 50PE)
2. Johkasou with screen and flow
equalization chamber ( > 50PE)

2 week

3. Other Johkasou ( > 50PE)(without screen equipment, etc.)

3 month8

Inspecting wastewater flow

Checking remaining disinfectant

Measuring transparency

Measuring
depositedsludgeAn Example of johkasou O&M
Explaining inspection results

Creating maintenanceinspection report

Blower inspection

Measuring circulating water volume9Measurement of residual chlorine

Check the water quality onsite(pH, DO, NO2, residual chlorine)
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pHDO

pH meter

DO meter

NH4, NO2, NO3

NH4, NO2, NO3 portable testing unit

NH4, NO2, NO3 test paper
11Preparation work

Drawing sludge out of the 1st-room ofanaerobic filter tank

Drawing sludge out of the 2nd-room ofanaerobic filter tank

An examples of johkasou desludging
Reporting the results of desludging to the owner

Filling the tanks with water
Cleaning the tank12

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