CHAPTER 12. Heavy Metals in Tannery Wastewater and Sludge: Environmental Concerns and Future Challenges

Abstract

Tannery wastewater is considered to be one of the most polluting effluents due to it containing a large variety of toxic heavy metals that range from chromium, cadmium, cobalt, lead, nickel, selenium to arsenic. As consequence of most tannery wastewater treatments, the tannery sludge that is produced contains considerable amounts of heavy metals, which are harmful to the environment and human health. Hence, tannery wastewater and sludge treatments have become a serious environmental issue. At present, the conventional options for sewage sludge disposal, such as fertilizers and soil amendment materials for the land and landfill, are widely applied. However, heavy metals in the tannery sludge often outweigh the soil's heavy metal content, and the application of sludge can indeed increase the concentration of heavy metals in the agricultural soil and affect the crop production owing to uptake of the metals. Research on devising appropriate treatment technologies for tannery wastewaters has gone through various phases of development over the past decades following developments in processes related to the leather manufacturing industry. This chapter attempts to revise environmental concerns and future challenges related to the management of tannery wastewater and sludge.