Measures taken against water pollution in basic non-ferrous metal industries.

Waste water purification is shown to be an important field of environmental hygiene for non-ferrous metal industries. Hydrometallurgy becomes of greater importance for metal production and refining. Quality standards for drinking water and rivers require a minimum of some harmful impurities, e.g. metal compounds. The unit operations of hydrometallurgy technologically parallel the methods of effluent treatment in the non-ferrous metal industries. Examples are given which show recent developments and ways of relieving lower degrees of waste water pollution: (1) Increase in the use of salt solutions for producing magnesium; (2) Measures for the prevention of air pollution during aluminium electrolyses cause new effluent problems to arise; (3) Wet or dry gas cleaning in the case of salt cover furnaces at aluminium re-melting plants; (4) Change in a process for copper cementation—copper(I) chloride as an intermediate product of metal recovery; (5) Ion exchangers as concentration steps for purifying waste water containing non-ferrous metals; (6) Waste water purification at an ISP plant; (7) Utilization of leaching residues from zinc electrolysis plants; (8) Use of waste lime for hydrometallurgical processes; (9) Recovery of special metals by means of ion exchangers; (10) Recovery of service water as a valuable product in the purification of waste water in basic non-ferrous metal industries. Nevertheless, some unsolved problems need better technical processes to reduce unfavourable biological effects produced by low concentrations of metal salts. Future developments in non-ferrous metal works have to examine the water economy conditions closely in order to meet the requirements for a higher metal yield and a better water purification.