The Control of Water Pollution and the Disposal of Solid Wastes in the Industries Producing Basic Inorganic Chemicals
An outstanding change since the last Congress in 1970 has been the greatly increased sophistication of the approach to environmental problems. It is no longer adequate to consider only the direct immediate local effects of manufacturing activity, but it is also necessary to take into account environmental effects, possibly extended widely in space and time, arising both from effluent streams and man's use of the products of these activities. The shortage of raw materials and energy has provided added incentive to reduce pollution by recovery of wastes for recycling or reuse. These trends are illustrated mainly by examples from the chior-alkali industry (the manufacture of chlorine, caustic soda, sodium carbonate and related chemicals), for this is the area in the manufacture of inorganic chemicals where there have been recently the most significant developments arising from environmental considerations. Experience with the discharge of mercury in effluents for chlor-alkali plants and the use of sodium polyphosphate in detergents illustrate the complex environmental problems which can arise from the manufacture and use of even relatively simple inorganic chemicals. Recent developments in the recovery of waste calcium sulphate from the manufacture of phosphoric and. hydrofluoric acids, probably the inorganic chemicals industry's most important single waste solids disposal problem, are briefly discussed. Because of the trend towards stricter international controls on discharges to the sea and the non-biodegradability of inorganic chemicals, the siting of plants on estuaries or close to the sea will no longer provide such a convenient method of effluent disposal as in the past and there will be increasing need for improved effluent treatment and the development of less polluting processes. The stricter controls on disposal to landfill will mean a much more scientific approach to this operation than in the past. In conclusion a plea is made for the use of cost benefit analysis to determine the allocation of the limited resources which can be devoted to improvement of the environment.