CHAPTER 16: Chromium in Tannery Wastewater Check Access

Chromium is found naturally in the environment in rocks, animals, plants, soil, volcanic dust and mists. Chromium is not found free in the most important deposits of the planet, it is found in elemental form or in the trivalent oxidation state. The conversion from trivalent to hexavalent oxidation state of chromium is an important feature, where hexavalent chromium predominates under highly oxidizing conditions. The majority of the chromium in the surface water may be in the form of particulate matter or deposited sediment. Industrial effluents containing chromium are discharged into rivers, soil and air. The results of several studies point to the need to control wastewater, considering that the improper disposal of chromium contributes to contamination of water resources and groundwater. The main human activities in which the chromium and its compounds are released into the environment result from the manufacture of cement and construction materials, welding alloys, foundries, manufacturing steel and alloys, electroplating industry, lamps, mines, urban waste and industrial waste incineration, coal ash, tanneries, fertilizers and wood preservatives. Solid wastes and wastewaters from leather manufacturing contain chromium. The use of chrome in the tanning process occurs with the trivalent chromium, usually in the form of basic chromium sulfate. The effects of chromium in the environment, water contamination by chromium, the process management and technologies of chromium usage in tanneries, the wastewater treatment operations and the chromium recovery will be addressed in this chapter.