2) Countermeasures against pollution from waste water

4,COUNTERMEASURES AT POLLUTION-GENERATING SOURCE

Waste water was roughly divided into 4 types: abandoned well water, benefication process water, sedimentation basin water and refining process water.
Countermeasures taken against each of these were as follows.

1. Abandoned well water
   In the mining process, some 10,000 cubic meters of well water gushes out of the ground per day. Therefore, a 1 ppb level of heavy metal dissolved in fresh water should not Consequently, well water was divided into fresh water and brackish water, with approximately 8,000 cubic The roughly 2,000 cubic meters per day of brackish water was run through. a thickener and solids were separated out, bringing cadmium concentration to 1ppb.
2. Benefication process water
   The benefication process requires about 10,000 cubic meters of water per day. About half of the water is contained in waste products and is sent to sedimentation basins, while the other half is recycled in a closed system.
   As a result, not onTy1 has cadmium discharge been prevented, but economic benefits have also been achieved such as increasing benefication recovery and As a result not onTy1 has cadmium discharge been prevented, but economic benefits have also been achieved such as increasing benefication recovery and minimizing the volume of required chemical reagents.
3. Sedimentation basin water
   Every day, abut 5,000 cubic meters of water contained in benefication waste, 5,000 cubic meters of waste conveyance water, 10,000 cubic meters or rain After treating the some 40,000 cubic meters or more of water contained in benefication waste, 5,000 cubic meters of waste conveyance water, 10,000 cubic meters or more of rain water, from into the sedimentation basin. After treating the some 40,000 cubic meters or waste per day, 20,000 cubic meters are used as industrial water and the remaining 20,000 cubic meters are After treating the some 40,000 cubic meters or waste per day, 20,000 cubic meters are used as industrial water and the remaining 20,000 cubic meters are discharged into the river system.
   Sedimentation is done using a cyclone to separate particles in benefication waste that are 75Um and larger in size from those that are smaller. The pond functions as a sedimentation basin for solid-liquid separation (A large volume or a The pond functions as a sedimentation basin for solid-liquid separation (A large volume or particles are contained in the water), The particle embankment functions as a earthen dam. The pond is treated with limemilk to keep pH to that of a weak base. Cadmium concentration is between 1 and 2 ppb (Fig.4-l).
4. Refining process water
   The refining process uses approximately 10,000 cubic meters of industrial water and 30,000 cubic meters of cooling water per day. Like benefication process water, process water contains a high concentration of heavy metals, therefore water is recycled, neutralized and subjected to rapid filtration .
   Owing to these countermeasures, the 8 ppb concentration of cadmium found in waste water and the 35 kg per day discharge volume of 1972, were reduced to one seventh by 1992, at 1.4 ppb and 5 kg per day respectively. These results show the efforts of taking countermeasures against waste water and brought down the These results show the efforts of taking countermeasures against waste water and brought down the concentration of cadmium in the water to roughly that of natural water (Fig.4-2).