Purification of the Mineral-Contaminated Water by Instillment through Bore Holes in the Matsuo Sulphur Mine

Abstract

It is customary to neutralize the acidic mineral contamination of mine water by alkaline material such as powdered CaCO₃ in sulphur mines. The author found a simple and non-expensive process whose installation in the Matsuo Sulphur mine accomplished the objective with satisfaction. The process consisted of using the purifying media of the soil-rock system such as ion-exchange, adsorption, neutralization, and filtration. The acidic mineral-contaminated water was poured into the earth through bore holes and such and the purified water was assimilated with the uncontaminated water flowing underground.
In order to execute the process, the following considerations were made:
(a) The stratum which has a great purifying power is composed of porous layers, such as a younger sedimentary layer (fan deposit, detritus and younger volcanic tuff, etc.) and not of compact layers such as igneous rocks and Mesozoic or Paleozoic sedimentary rocks. Furthermore, the ground-water layer which is to receive the mineral water must possess a free water table which is beneath the earth's surface. Accordingly, it is necessary to seek a territory which has these qualifications.
(b) The area along the river near the sulphur mine is generally already contaminated to some extent, the pH being as low as 3.0. In order to avoid enlarging the contaminated ared, it is necessary that the installation positions of the instillment bore holes are located in this already contaminated area, and not in the noncontaminated stream district.
(c) The purification power of the soil-rock system in general decreases gradually with the increase of the instillment. However, depending upon the texture of the soil-rock system, it is possible that a rapid loss of the power can occur. For such an eventuality, it is necessary to pour the contaminated mineral water into a new area. Consequently, it is necessary to be able to shift at will.
(d) Since the loss of the purification power of the soil-rock. system is liable to introduce a momentous effect at down-stream territory by exposing the injected acidic water at the earth's surface, it is of utmost importancee to perceive and control the underground condition sufficiently at the instillment territory. It follows that the selection of the territory should be made so as to afford reliability and facility of the control operation.
The installation was commenced in July of 1952. A brief description follows.