Studies of levels of selected heavy trace metal ions in industrial waste effluents from industrial Estate, Karachi

The impairment of water quality due to introduction of industrial pollutants is a major problem faced by big industrial cities. The uncontrolled release of waste effluents of large water bodies have deleterious effects both on water quality and aquatic life. In our country, Karachi, the largest industrial city, is facing a similar problem. The aim of the present work is to determine the levels of heavy trace metals in the effluents of different industries in Karachi industrial estate. The samples were collected directly form waste outlets and given proper treatment for storage. The concentration of various metals were determine using complexometric method followed by UV/visible absorption at suitable wavelengths. The minimum level of Cr(1.25 ppm) detected was more than permissible limits as dictated by international agencies (1.0 ppm for trivalent and 0.5 for hexavalent Cr). The minimum concentration of Co in the liquid waste was found to be 0.9 ppm as compared to the recommended dose of 0.2-2.0 ppm. Suggestions are given to control these levels with limits by using chemical methods. Need of strict legislation is also being emphasized. (authors)