Tannery industry fulfills a growing international appetite for leather and earns a large amount of foreign revenue. But the tanneries which are located at Hazaribagh are the major cause of Buriganga river pollution. Tanneries of that area do not contain any treatment plant for treating their chemical effluents coming from tanneries processing. These tanneries discharge their liquid chemical and solid wastes into the river Buriganga. As a result Buriganga river pollution has reached to extreme level and its polluting rate is increasing rapidly.
4.2 Wastes of Tanneries
Tanneries of Hazaribagh produce a large quantity of solid and liquid wastes at the time of processing of hides and skins of animals.
Table.4.1: Average amount of wastes produced by Dhaka Hides and Skins Limited
|Waste Type |Waste Amount (ton) |Percentage (%) | |Solid |2 |9 | |Liquid |20 |91 | |total |22 |100 |
Source: Questionnaire Survey (: July, 2012)
It has been seen that, tanneries produces more liquid toxic waste than solid waste, which are mostly responsible for water pollution on Buriganga.
Tanneries of Hazaribagh produce 25000 tons of solid waste and 40,000 tons of toxic liquid waste everyday (Daniel 2010).
Processing and production of leather and leather products are finished in three sectors, named
a) Wet Blue – processing of raw hides.
b) Crust – coloring of leathers.
c) Finishing – producing leather products.
Figure 4.1: Percentages of waste from three sectors. Source: Questionnaire Survey. Date: July, 2012.
Most of the wastes are produced at the primary stage of raw skin Processing.
4.2.1 Solid Waste
250 tanneries located at Hazaribagh produces 150 metric tons of solid waste everyday. These solid wastes are being produced at the initial and final stage of processing.
Solid wastes produced from tanneries includes:-
• Shaving Dust – while processing raw hides and skins.
• Scarp of hides and skins.
These solid wastes are being reused and produce leather boards, Zyllatic, Chicken feed, fertilizer, soap etc.
4.2.2 Liquid Chemical Waste
Liquid chemical effluents are produced during tanning and dying. Different types of Chemicals are being in tanneries at the different stages of leather processing, including processing of raw hides and skins, chrome tanning – turning a skin into bluish white colored leather.
These chemicals includes:-
• Sodium Sulfide
• Sulphuric acid
• Sodium hydrosulfide
• Caustic Soda
• Arsenic Sulfide
• Calcium hydrosulfide
4.3 Buriganga River Pollution from Tanneries
Water pollution of Buriganga river is being affected and accelerated by 250 large and small tanneries located at Hazaribagh, at the bank of the Buriganga. These tanneries do not have any effective waste treatment facilities or any treatment plant.
Figure 4.2: Status of treatment plant containment by tanneries. Source: Questionnaire Survey. Date: July, 2012.
The diagram represents that nearly 99 percent of tanneries do not contain any treatment plant, less than 1 percent tanneries contain treatment plants. As these tanneries do...