Reuse of Pickling and Chrome Tanning Liquor and Treatment of Tannery Effluent
Kamruzzaman Khan 1*, Eshita Jhahan 2
1 Department of Industrial and Production Engineering, Bangladesh University of Engineering and Technology, Bangladesh
2 Department of Leather Engineering, University of Dhaka, Bangladesh
Leather industries in Bangladesh are polluting water and air severely. Among all the operation carried out in the tannery, pickling and chrome tanning are the leading pollution causing processes. The prevalent standard operating procedure of pickling, and chrome tanning causes pollution since the tannery owners in Bangladesh often discharge untreated pickling liquor and add extra chromium salt to expedite the chrome tanning process instead of adding a catalyst. This study was carried out to evaluate the re-use capability of the pickling and chrome tanning liquor without compromising the quality of leather. Later, the discharged effluent was treated with the locally available chemicals, especially available in tannery for purification. The results showed that the addition of 0.2% sulfuric acid (10 times diluted) and 0.1% formic acid (10 times diluted) in the old pickling bath and the addition of 5% fresh basic chromium sulfate in the used chrome liquor made the liquors efficient to re-use in the new tanning process. A slight change in the design of the common effluent treatment plant (CETP) is required to collect the used pickling and chrome tanning liquor. After re-using the pickling and chrome tanning liquor, the discharged effluent was treated to purify with the help of chemicals and adsorbents available in a tannery. The change in the biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solid and chrome removal efficiency of discharged effluent after treatment was 95.4%, 84.6%, 98.5% and 66.7%, respectively. These results revealed that the cost associated with the processes and reduction of pollutants would make it a practicable method in the local tanneries of Bangladesh.