Home > JOGMEC's Activities > Mine Pollution Control > Mine Pollution Prevention Technologies : Administration and Control of a New Neutralization Plant at the Abandoned Matsuo Mine
Administration and Control of a New Neutralization Plant at the Abandoned Matsuo Mine
An advanced neutralization and treatment facility run by JOGMEC has restored the Kitakami River to its former clean state.
Background
The Kitakami River is a clean stream typical of the Tohoku district; swans fly over in winter and salmon swim up the river in autumn. In the 1970s, however, acidic water that had not been treated adequately flowed into the river from the closed Matsuo Mine, making the river brown and muddy and causing great societal problems. What brought the river back to the clean stream we see now is a new neutralization and treatment facility at the abandoned Matsuo Mine that is being operated by JOGMEC.
New neutralization and treatment facility at the abandoned Matsuo Mine
Located in the middle of Hachimantai, 1,000 meters above sea level, the abandoned Matsuo Mine is the largest sulfur mine in the Far East. The mine site was discovered as a large outcrop of a sulfur ore deposit in 1882. In its most prolific period, as many as 15,000 people lived nearby, and the prosperity of the mine peaked. From the 1960s, however, mine operations worsened due to the market debut of sulfur recovered cheaply through desulfurization of heavy oil in response to regulations on pollution; in 1972 the mine was closed. Even after the mine was closed, however, large volumes of strongly acidic water continued to flow from the mine and empty into the Red River nearby. To neutralize this water, a neutralizing agent was poured directly into the Red River, and as a result, brown muddy water polluted the Kitakami River downstream, engendering great societal problems. A committee with representatives from five government ministries - including the former Ministry of International Trade and Industry (MITI) and the Ministry of Construction - studied countermeasures, and it was decided in 1976 that a large-scale neutralization and treatment facility would be constructed. The facility was constructed by Iwate Prefecture, with assistance from the former Ministry of International Trade and Industry (MITI), and operation was delegated to the Metal Mining Agency of Japan (MMAJ), a precursor of JOGMEC.
Current Status
Full-scale operation began in April 1982, and has been continuous since then, neutralizing and treating large volumes of mine wastewater at around 18 tons per minute; this is strongly acidic wastewater of about pH2 that also contains large quantities of iron and arsenic. After sediments have been separated, only supernatant water is released into the Red River. In parallel with this undertaking, to reduce the amount of water inside the mine and the amount permeating from it, construction work on water generation sources was carried out up to FY2002 by the Iwate Prefectural Government, and JOGMEC also provided support for this endeavor.
Confluence of the polluted Matsu River (Red River downstream) and the Kitakami River (at closure of the Matsuo Mine)
Construction of this neutralization and treatment facility cost roughly ¥10 billion, and over ¥600 million was spent each year to maintain and operate it. From FY2000-2004, however, comprehensive verification tests on energy conservation were conducted, and costs were reduced by about ¥40 million. Electric power consumption, for example, was reduced by 26%. Water released from the facility has also increased in quality.
