Abstract:
Tanneries consume huge amount of water and chemicals each year and release effluents into the environment. Effluents produced from different stages of leather processing like the soaking, liming, chrome tanning, rechroming, neutralization, fatliqouring and dyeing processes can reduce surface water quality and damage human health. Pollutants generating from each stage of tanneries vary in concentration. So, proper study on characteristics of effluents from leather process can help to reduce water pollution. On the other hand, Water footprint can help to understand the water management of the leather sector in Bangladesh. Water footprint is actually an indicator of fresh water consumption in making a product in its life cycle. Water footprint data includes blue water footprint indicates surface or ground water, green water footprint indicates rain water and grey water indicates assimilation water of pollutants in effluents. The results from this study indicate that significant environmental impacts were caused during the leather production. Waste water samples have been collected from each stage of four tanneries for this study. The key pollution indicating parameters (pH, TDS, TSS, BOD and COD) have been analyzed for each sample. Those data have been used to calculate pollution load associated to different leather processing stages. It is found that almost 52% effluent generates from beam house and tan yard operations and 48% from post tanning operations. Almost 87% effluent generates from beam house in wet blue production. Effluent generates mostly from soaking (21%) and liming (34%) process of tannery. Maximum COD has been found in liming 142 kg/ton, then soaking 54 kg/ton and retanning 54 kg/ton. TSS has been high as well in tannery effluent such as in liming (121 kg/ton) and then neutralization (55 kg/ton). The control and reduction of soaking and liming effluents are the critical points to be considered to improve the environmental performance of the process. The Water footprint of bovine and ovine crust leather has been found to be 34000 m3/ton and 17300 m3/ton respectively. Water footprint assessment shows that grey water footprint of leather is almost 40-50%, blue water footprint of leather is almost 10-20% and green water footprint of leather 30-40% in total water footprint of leather from Bangladesh. Blue water footprint is higher in soaking, liming and finishing. Green water footprint does not belong in the processing stages of leather. Total green water footprint of leather mainly comes from green water footprint of feed crops of the farming animals. Grey water footprint is higher in soaking, liming, Fatliqouring and dyeing stages. So, by assessing water footprint and pollution load data, this study can help to understand the water footprint and pollution scenario of leather sector in Bangladesh.
