Menu

Close

Here's the text.

Radioactive material concentration in sewage sludge

Last Updated October 31, 2024

Reason for the inclusion of radioactive materials in sewage sludge incineration ash

The radioactive material diffused following the accident at the Tokyo Electric Power Company, Incorporated Fukushima Daiichi Nuclear Power Station reaches Yokohama City due to atmospheric flow, flows into sewer pipes due to rain, etc., and reaches the Water Reclamation Center. Sewage is treated at the Water Reclamation Center and the Sludge Recycling Center, and eventually becomes sewage sludge incineration ash. As mentioned above, radioactive materials flowed into the sewer pipes, so sewage sludge incineration ash also contained radioactive materials.

Figure of the flow of radioactive materials contained in sewage

History of Sewage sludge incineration ash

September 9, 2011 Announced landfill at Minamihonmoku landfill

  • Safety confirmation of landfill of sewage sludge incineration ash → Landfill announced on or after September 15

September 14, 2011 Freeze landfill at Minamihonmoku landfill

  • Since the explanation was insufficient to the people concerned, the landfill was "freeze" until sufficient explanation was given.
  • We explained to citizens and related parties using materials that explained the contents of the "Safety Evaluation Study Report on Landfill of Sewage Sludge Incinerated Ash at Management Type Disposal Site" in an easy-to-understand manner. .

We proposed future correspondence plan of sewage sludge incineration ash in September, 2013 and explained to citizen, related people. .

July 2014 In addition to the improvement to date as a Hijiwara fee, recycling as a construction material began.
Dec. 2014 Dec. 2014 The Company decided to reclaim incinerated ash from April 2014 onwards in the land area of Minamihonmoku landfill.

From February to March 2015, a mixed ash mixture of Resources and Waste Recycling Bureau's main ash and sewage sludge incineration ash was carried out at the Minamihonmoku Waste landfill.
July 2015 Landfill commenced in the same way as reclamation.
September 2017 Completed landfill at the Minamihonmoku Waste landfill.
Current     Continued disposal through improved soil and resources as construction materials.

Radioactive material concentration in sewage sludge


Radioactive material concentrations in dewatered sludge, sludge incineration ash, and improved soil are as follows.

Unit (becquerel/kg)
NameHokubu Sludge Treatment PlantNambu Sludge Treatment Plant

Dewatered sludge

Sludge incinerated ash

Improved soil

Dewatered sludge

Sludge incinerated ash

Date of sampling

2024
September 2

2024
September 30

2024
September 24

2024
September 2

2024
September 30

Cesium-134Non-detectionNon-detectionNon-detectionNon-detectionNon-detection
Cesium-137

Non-detection

41.0Non-detectionNon-detection

55.6

※Non-detection indicates that the detection limit is below the detection limit.

※We started measuring iodine-131 as an index to confirm the effects of the nuclear accident, but based on the fact that the half-life of iodine-131 has already passed three years or more, September 2014 From 1st, there are two items, cesium-134 and cesium-137, excluding the measurement items.

Sludge incinerated ash is stored in the northern and Nambu Sludge Treatment Plant sites.


Changes in storage status of incinerated ash and concentration of radioactive materials

  1. The current and past storage status of sewage sludge incineration ash is as follows.

Storage status of sewage sludge incineration ash (PDF: 613KB)


The storage status of sewage sludge incineration ash was nearly 38,000 tons in the south and Hokubu Sludge Treatment Plant at its peak, but the disposal has gradually decreased. However, the situation has to be placed in the hall, which affects the operation of the facility.

On the other hand, the concentration of radioactive materials incinerated ash in sewage sludge has been reduced to less than one-tenth of the level compared to the beginning of storage.

  1. The spatial radiation dose rate at the site boundary is as follows.
Unit (microsievert/hour) 
NameEast sideWestSouth sideNorth sideDate of measurement
Hokubu Sludge Treatment Plant (Suehiro-cho, Tsurumi-ku)0.050.050.040.05

2024
September 13

Nambu Sludge Treatment Plant (Koura, Kanazawa-ku)

0.05

0.060.05

0.06

2024
September 13

※Measurement at a point 1 meter high from the ground

Other radioactive material concentrations

  1. Inflow sewage and discharge water
  1. Radioactive substance concentration in exhaust gas
  1. Radioactive material concentration data of Minamihonmoku landfill mixed ash PDF (PDF: 63KB) excel (Excel: 50KB) 
    (The landfill disposal ended in September 2017)

Materials, etc.

※"Figure 3-4 Radiation Exposure around People" on page 20 of this explanatory document has been updated with the data from the source. For more information, please refer to the following URL.
http://jccu.coop/food-safety/qa/pdf/qa03_03_02.pdf (external site)


You may need a separate PDF reader to open a PDF file.
If you do not have it, you can download it free of charge from Adobe.
Get Adobe Acrobat Reader DCTo download Adobe Acrobat Reader DC

Inquiries to this page

Sewer River Bureau Sewerage Facilities Department Facility Management Section

Telephone: 045-671-3965・3966

Telephone: 045-671-3965・3966

Fax: 045-641-4870

Email address: gk-shisetsukanri@city.yokohama.jp

Return to the previous page

Page ID: 681-048-429

Menu

  • LINE
  • Twitter
  • Facebook
  • Instagram
  • YouTube
  • SmartNews