Suitable measures against the pollution of the Rhine by chloride discharge from the Alsatian potash mines.

A great number of organic and inorganic substances pollute the water of the Rhine. The greatest concentration is formed by the chlorides, as their quantity exceeds that of the suiphates by about 50 per cent. At the German—Dutch frontier, the mean annual value of the chloride charge of the river amounts to approximately 350 kg/s C1. About 40 per cent, or 130 kg/s, of this quantity are residual salts originating from the French potash mines in Alsace. As the chloride charge of the Rhine causes considerable damage to Dutch horticulture and the public supply of both drinking water and industrial water, a solution for the problem of the salt discharges in Alsace is sought within the framework of the International Commission for the Protection of the Rhine from Pollution. By means of a separation process, KC1 is extracted from the sylvinite hauled from the mines (58 per cent NaCI, 28 per cent KC1 and 14 per cent marl), while the residual salt, about 7 million tons per year, is drained off into the Rhine. Non-realizable solutions for effecting a reduction of this discharge are: (1) Measures within the production process (2) Filling of the residual salt into the hollow spaces left by mining (3) Sale of the residual salt to soda works (4) Discharge, through a pipeline, into the sea One possible solution would be deposition in a dumping area, but this might endanger the rich ground-water resources of Alsace. At present, a two-year hydrological investigation at a 20 m high trial pile is being complemented by studies on suitable sealing, piling and transporting techniques at different locations. The possibility of transportation by ship has also been taken into consideration. For this purpose, another investigation is actually being carried out.