This report was written following a two-week reconnaissance trip to Japan in late May
and early June of 1993 by the author. Visits were made to a cross-section of
government, industrial and university laboratories and research institutes engaged in
acid-mine drainage studies. Introductions and appointments had been arranged in
advance by a Japanese colleague and researcher in the field.
Most of the groups visited had been actively involved in this kind of research for the
past two decades. There was found to be a high degree of collaboration and unanimity
of purpose between the various sectors involved in the research to the extent that one
could almost consider it an integrated national effort. This is surprising, considering
that there is now very little mining carried out in Japan, although the smelting of
imported ores and concentrates continues to be a major industry. There appeared to
be a consensus that the development of new treatment technologies will form the basis
of a lucrative new industry both nationally and internationally. In addition, it is accepted
that to protect those of its mineral supplies originating in developing countries, Japan
must assist these countries in all aspects of mineral exploitation, including
environmental protection measures.
Some new technologies have been fully developed and successfully introduced,
notably those based on the bacterial oxidation of ferrous iron, such as the Matsuo Mine
acid drainage treatment plant, the Dowa Mining Company’s flue-gas de-sulphurization
system, the flue-dust treatment system in operation at the Dowa Mining Kosaka
smelter and the recovery of marketable ferric sulphate solution at the Kosaka smelter.
The Ferrite and Iron Powder processes developed at two Tokyo universities are also
now widely used in Japan for the treatment of metalliferous industrial effluents. The
sludge-densification process based on re-cycling precipitated sludge particles from the
settling tank back to the neutralizing tank, is being successfully operated in several
plants.
Other new technologies have been extensively developed, but not yet introduced.
These include systems for the recovery of ferrite and hematite from iron-rich mine
drainage waters and a flotation process for the recovery of a range of metals from mine
drainage waters.
At the present time, a whole range of new technological approaches is being
examined, but are in the early or middle stages of development. The most important of
these are processes involving ion-exchange technology, membrane technology,
sulphate-reducing bacteria, sulphur-oxidizing bacteria and metal-absorbing organisms.
Also, plans to use the stopes in abandoned mines for the disposal of sludges and solid
wastes are being seriously investigated.
The main recommendation of the report is that the setting-up of a new research fund
specifically designated for joint Canada-Japan collaboration in the field of acid mine
drainage be explored. Financing of this new funding source to be shared by the Mine
Environment Neutral Drainage (MEND) program and the Metal Mining Agency of
Japan (MMAJ).
