Emerging Contaminants of Tannery Sludge and Their Environmental Impact and Health Hazards

Water pollution caused by various industrial effluents has been increasing on a tremendous scale due to rapid industrialization. One of the blooming and revenue-generating industries is the tannery industry with an annual turnover of around 7.8 billion euros. However, the tannery industry uses various toxic heavy metals (e.g., chromium (Cr), cadmium (Cd), lead (Pb), nickel (Ni), etc.) in the leather tanning process and also generates various kinds of wastes, such as proteins, lime, hair, salts, acids, dyes, tannins, oils, etc. Sludge produced from the physical-chemical treatments of tannery wastes are called tannery sludge (TS), a type of solid waste. Cr salts are extensively used as tanning agents to give leather good mechanical and hydrothermal resistance. The third-most hazardous and carcinogenic substance, namely, hexavalent chromium, is present in tannery sludge. Such hazardous tannery sludge are disposed into the environment, thus causing both water and soil pollution. The rapid growth of industrialization and urbanization has increased the amount of toxic wastewater disposed by various industries into water bodies and environments, with ~80% of the wastewater containing harmful chemicals, e.g., heavy metals, carcinogenic dyes, etc. Numerous types of health hazards are caused by the consumption of polluted water. The World Health Organization (WHO) has reported that ~25% of health diseases are triggered by pollution (soil, air, and water pollution). This chapter provides detailed information on the emerging contaminants of tannery sludge and their environmental impact and health hazards, a discussion on their management as well as challenges and future perspectives, and a chapter summary as conclusion.