Membrane technology in tannery wastewater management: A review

Abstract

The leather industries is a key and viable sector of the economy of many emergent countries, but it is also recognised as one of the highest polluting industries. This is as a result of the discharge of vast amounts of chemical containing water employed in the leather making process into the environment with little or no treatment. Nearly 40-45 litres of water are used per kilogramme of raw hide processed into finished leather. However, of the total amount of water employed in the leather making process approximately 90% is discharged into the environment as effluent. As such, a large amount of noxious effluent is produced having huge chemical oxygen demand and biochemical oxygen demand, suspended and dissolved solids, chromium, surfactants and other toxicities. It is therefore vital to adequately treat/detoxify the tannery wastewater for environmental safety. Various methods are available for the treatment of tannery wastewater. The numerous physiochemical techniques used for wastewater treatment can also be applied to tannery wastewater (to the entire process or to individual step in the process). However, conventional treatment methods have certain limitations in real field of tannery wastewater treatment arena. Membrane technologies gain importance in this regard. This paper provides an insightful review on the environmental pollution and toxicity characteristics of tannery wastewater and chemicals. Moreover, traditional treatment methods, their advantages and disadvantages, for tannery wastewater are briefly discussed. Membranes, their classifications and available preparation techniques are briefly reviewed. Finally, advances in the membrane treatment approaches used for the treatment and/or detoxification of tannery wastewater at both laboratory and pilot/industrial scale are evaluated. In addition, integrated membrane treatment approaches alone or in combination with physicochemical and biological treatment approaches are also considered.