Measures against water pollution in industries producing basic inorganic chemicals including fertilizers

Abstract

The chemical industry began at an early stage to take pains to make further use of unwanted by-products from chemical reactions. When these products became a nuisance to the environment, further processing became a necessity. Economic interest was also involved in many caseS. Thus the barium chloride solution obtained in the production of lithopone is converted into BaSO4 or BaC12. By the Claus process sulphur is reconverted from CaS, the waste product of the Le Blanc soda process. However, many processes have waste products which can only be put to further use with difficulty. Increasing industrialization and population density limit the possibility of dumping these substances in rivers. The method of biological processing which has proved successful for organic waste is restricted to exceptional cases. Most of the remaining processes are costly. Waste sulphuric acid from the production of pigments and dyes is either boiled down and the salt thus achieved converted into SO2, or it is transported out to sea where it is pumped out to be diluted with sea water to a high degree. The residue from the production of hydrogen fluoride from fluospar is converted into anhydrite and sold to the building industry. In many cases the problem of waste products can be solved by changing the method of production. One example of this is the production of Ti02 by the titanium tetrachloride process instead of by the sulphuric acid process. The best position for production processes where inavoidably large quantities of waste salt are produced is on the coast. The possibility of the sea as a dumping ground will become increasingly important for the industry in the future. EFFLUENT PROBLEMS IN THE CHEMICAL INDUSTRY In chemical processes new substances are obtained from existing ones through reactions between materials in the gaseous, liquid, or solid state. But as the end products of chemical reactions are not always saleable, those of them which represent undesirable by-products have either to be discarded or fed back into the production process after suitable treatment. Where the latter has been commercially rewarding it has always been the more attractive course. In addition attention has been paid for many years to the problems of disposal and