Test operation of river water filtration system on Abukuma River

  • The test operation of the river water filtration system which is being developed by IER and Fukushima University was conducted in an experiment in Abukuma River on 19th Novermber, 2013 by the team led by Professor Kenji Nanba, Vice Director of IER.
    The filtration system is used to collect suspended solids (SS) in river water necessary to clarify the behavior of radioactive substances in the environment.
    Abukuma River is a First Class river (in Japanese river classification system) that originates from Nishigo Village in Nishi-Shirakawa County and runs through major cities of Fukushima Prefecture such as Shirakawa, Sukagawa, Koriyama, and Fukushima. It then passes Miyagi Prefecture and eventually empties in the Pacific Ocean at the border between Iwanuma City and Watari Town. Its catchment area covers approximately 5,400 square kilometers that include regions with a comparatively higher level of contamination caused by the Fukushima nuclear accident.
  • Sample collection site

    SS samples are collected on the east shore of Abukuma River at Kuroiwa, where the water level monitoring station of Ministry of Land, Infrastructure, Transport and Tourism (MLITT) is located. The radioactivity level of the river water will be calculated using the water level data at this site measured by MLITT.
  • A distant view of the sample collection site

    The elevation from the water surface to the top of the bank was approximately 10 meters on that day. As there is no road for the truck to go down to the shore, the water had to be sucked up with two pumps to the truck, on which all the equipment is mounted.
  • Testing of improved filtration block

    SS samples are collected by passing the river water through the filtration block with a multiple layer of glass fiber filters. This fitration block is developed by Prof. Takayuki Takahashi, Director of IER, based on the model that was devised in Ukraine after the Chernobyl accident. By using 3D printing technology, Prof. Takahashi has been endeavoring to make it smaller, lighter, and more efficient. The new model is capable of filtering 60 liters of water in approx. 15 minutes.
  • Centrifugal separation of suspended solids

    SS samples are also collected by using a continuous centrifugal separator. This is done on a weekly basis as a part of a government study to depict the distribution of radioactive substances from the Fukushima nuclear accident. A centrifugal separator is capable of collecting a larger quantity of samples than filtration, which enables the provision of more samples for a wide range of analysis. The supernatent water separated by centrifugal separation also contains radiocesium, which will then be removed by coagulation sedimentation as well as by Prussian blue filtration for radioactivity measurement.
  • Collection of samples with a plankton net

    Prof. Nanba and his team also collected SS samples by using a plankton net with the mesh size of 41 micrometer. The purpose of this is to compare its effectiveness and efficiency as a sample collection method with that of the filtration system or the centrifugal separator.