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Name of the Researcher: Md. Ariful Islam Juel
Name of the Department: Department of Civil Engineering
Name of the Institution: Bangladesh University of Engineering and Technology (BUET)
Name of the Title: Stabilization of Tannery Sludge through Brick Production

Introduction
Leather industry in Bangladesh is considered as one with considerable growth and investment potential, earned $1.29 billion from exports in the 2013-14 fiscal which accounts for 4.2 percent of the country’s total exports (Hashem et al. 2015). The 113 tanneries which are mostly situated at Hazaribagh area, produce 180 million square feet of hides and skins per year and they generate about 20,000 m3 of wastewater containing 2500-12500 mg/l suspended solid (HUFFER and TAEGER 2004). In wastewater treatment process, different chemicals are added and most of the chemicals get settled out during the process. Finally they end up in the sludge. Due to inherent nature of training process the tannery wastewater contains a large amount of suspended solids, resulting in generation of sludge in effluent treatment plants. About 100-150 kg of dry solid matter is generated per ton of hides/skins processed (UNIDO 1998). In Bangladesh 85000 tons of wet salted hides and skins are processed annually and it is estimated that 19000 tons of partially dried (50%) sludge will be generated by the effluent treatment plants if all tanneries treat effluent. In conventional physic-chemical cum biological treatment system 70-80 per cent of the sludge is produced in the primary treatment and the remaining 20-30 per cent is produced in the secondary biological treatment. The solids content in the tannery effluent will depend upon the raw material, type of process adopted, chemicals used in the process and other in-plant control measures. The main sources of suspended solids generation are first soaking, liming and vegetable tanning that too if carried out in pits using crushed barks and nuts. Tannery sludge, an unwanted solid residual from the tannery wastewater treatment plant, has the potential to contaminate soil, surface water and groundwater by generated leachate and pose a threat to the environment and natural resources if the sludge is not disposed properly (Thomson et al. 1999). Tannery sludge contains elevated concentrations of heavy metals like As, Cr, Co, Ni, Cu, Zn, Fe, C dude to use of basic chromium salt, different syntans, dyes, pigments, retaining agents etc. in the tanning process. These heavy metals are very harmful, because of their non-biodegradable nature, long biological half-lives and their potential to accumulate in biological systems (Manahan 2005, Wilson and Pyatt 2007, Singh et al. 2004). A technique to treat or stabilize hazardous waste is by solidification in construction materials such as brick or concrete which has been applied in several instances for the cases of sewage and textile sludge and arsenic-rich filter materials (Cusido oand Cremades 2012, Rouf and Hossain 2003). Several studies have shown that this technique can be applicable for tannery sludge as well (Basegio et al. 2002). The solidified product may be disposed off to a secured landfill site or it can be recycled as construction materials if it meets the specific strength requirement and can be shown to leach toxic pollutants within acceptable limits (Rahmat 2001).
Specific research objectives

The objectives of the study were to investigate the tannery sludge management through brick production. Since Bangladesh is a developing country brick s are used in a large extent for the building construction. To meet the demand of millions and millions of bricks, a large number of brick fields have been established and increasing day by day. For this reason a tremendous pressure are falling on soil for raw materials of bricks resulting the reduction of agricultural fields. So the tannery sludge can be vital substitute of solid to some extent for the brick production which on the other hand, will reduce the environmental burden regarding sludge disposal. Different measurements of both clay – sludge mixture and bricks were carried out to evaluate the factors that could affect brick quality.
Major findings

For more information on this research, please contact the National Resource Centre, NGO Forum for Public Health, E-mail: nrc@ngof.org