Introduction

Non-ferrous metals besides gold, silver and platinum are somewhat toxic to living organism. It is therefore important that all the metallurgical industries not only take care of the process of manufacture but also safe disposal of the pollutants generated in the form of solids, liquids or gaseous wastes. Metallurgical industries generate vast quantities of solid wastes such as slag, ash, sludge, dross, grindings, turnings, clippings, residues and secondaries. During the last few decades rapid industrialization has led tomany fold decline in the quality of environment. Some of the solid wastes produced during metal extraction are hazardous in nature, since they contaminate the surface and ground water through the leachate generated at the dump-sites, which is a risk to the life of the living organism. Effects of pollution due to the toxic constituents of the above leachate, are usually noticed in the long run. It is for this reason that the industries are not much concerned about the solid metallic wastes that are invariably thrown and dumped unsystematically during metal production. The type of metallic waste generated, depends on the quality of raw materials used, the process and the treatment methods. Irrespective of the physical forms such as solid, liquid and gas, the wastes generated are eventually of two types: hazardous and nonhazardous. Amongst the heavy and toxic metals, arsenic, cadmium, chromium, nickel, lead, copper, mercury and zinc are considered deleterious to the environment, when their concentrations are more than the stipulated limits. The major environmental degradation is caused by copper, lead and zinc industries, often using imported zinc ash/residue, dross, skimming, lead scrap etc. It has therefore become a major issue enforcing agencies to take policy decisions regarding import of such wastes and identifying the industries having environmentally sound technology.

As the leachate generating from the dumping of the hazardous wastes contaminates the environment, efforts must be directed towards not only effectively monitoring and managing the environment but also developing and applying viable and acceptable ecofriendly processes and waste handling/management technologies to cater to the pollution free environmental control of even the small and medium scale industries.

With a view to assessing the environmental problems associated with hazardous constituents of these materials, National Metallurgical Laboratory (NML) has developed a valuable database information bank on Indian ferrous and non-ferrous industries detailing quantity and composition of the various solid wastes/secondaries generated, processing options for such materials and their management. This paper deals with an overview of the non-ferrous process industries (data on all the major and those minor industries which co-operated to give the information) and their attempts to save the environment from degradation. The attempts for the development of Process for the utilization of various wastes of non-ferrous industries, at NML are also highlighted.