CHROMIUM REMOVAL FROM TANNERY WASTEWATER: A REVIEW

Abstract

Tanning process generates high strength wastewater containing heavy metals, nutrients, organic and inorganic contaminants, which may adversely affect public health and the environment. The wastewater contains considerable amounts of heavy metals including Cr(VI) which is carcinogenic, mutagenic and teratogenic, and persistent in the environment. Several physico-chemical treatment approaches were employed in tannery wastewater treatment and proved to considerably reduce the level of toxic Cr and other pollutants to low concentrations. Despite the capabilities of physico-chemical treatment methods in treating high concentrations of toxic effluents, they are associated with setbacks including low removal efficiencies, high cost of chemicals, high energy requirement as well as low nutrients removal from the wastewater stream. Microalgal wastewater treatment systems can play an important role in bioremediation of tannery effluent and are considered as low-cost, efficient treatment alternatives that can potentially remove organic and inorganic contaminants, heavy metals, and possibly reduce the toxic Cr (VI) to a much less toxic Cr (III), especially when coupled with activated carbon.Keywords: microalgae, effluent, chromium, activated sludge, absorption, heavy metals