Research and chemical operations. The conversion of outer coverings

topic: A
case study on characterization of solid waste & discharged effluents of
Tannery Estate Dhaka (TED)



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a stabilized and imperishable natural fabric of fine texture is obtained from raw
(green) or preserved (Salted) hides and skins of animals by tanning through involvement
of both mechanical and chemical operations. The conversion of outer coverings of
carcasses which is a by-product of meat industry, into leather practiced by the
primitive people from ancient time has become one of the most prime-concerned global
industries in world economy. The leather industry, well known as user of
natural resources is always not only given priority for its economic dominance
but also for environmental influence as it generates pollutant wastes having
hazardous impact on environmental degradation.. These wastes are largely
generated during leather processing and effluent discharge. For this without
proper control of disposal of wastes, the leather industry is now regarded as
highly potential polluter industry. In the conversion of 1 ton wet
salted hides, 500 kg of different chemicals, 40  of water (process and technical water) and
2600-11700 kWh energy is consumed but only 200-250 kg of finished leather (grain
and embossed split) is achieved containing only 72 kg chemicals inside which is
only 25.5% of the total used raw materials and discharge approximate 600 kg of
waste in different forms. The wastes generated by the tanning industries are classified into
three groups such as liquid, solid and gaseous in nature and are enlisted in
the figure I.

Types of wastes generated from tanneries during leather processing

The tanneries
generate around 6 million tons of solid waste as trimmings (both tanned and un-tanned),
splitting, shaving & buffing dust and sludge (both chrome contained and
non-chrome) at
an average of 80% in leather processing per annum. During beam house and post tanning
operation, most of the solid wastes (trimmings, fleshing, splits and shaving
dust) are generated, containing small amount ( 2-6% (w/w)) non-chrome mineral
substance and influenced by quality of hides/skins, tanning technique and
condition process in characteristics. Moreover, useless splits, shaving dust
and unnecessary cuttings carry 3-6% (w/w) of fat and about 15% (w/w)
of mineral components, including 3.5%-4.5% (w/w) of chromium as  generated from tanned leather.  Sludge from wastewater treatment plant
generally bears water (up to 65% (w/w)), organic materials (30% (w/w)) and
chromium (iii) compounds (approximately 2.5% (w/w)).These solid
wastes are might of limited implementation but possess serious environmental problem
without safe disposal and treatment. Though
countries in the west are now shifting away from this industry, leather processing
is still an unavoidable source of earning foreign money and export trade for
many developing and under-developed countries. In Bangladesh, the leather industry
is relatively an older industry with an age-old tradition of over seven decades
has significant involvement of producing such leather, recognized for its
superior grain pattern and strong fiber strength worldwide since 1940.
According to the annual report of Bangladesh Economic Review of 2017, leather sector
is ranked third in terms of earning foreign money and around 1234 million$ achieved
from this sector in fiscal year 2016-17. To keep this momentum steady, the
leather industries situated in the capital’s Hazaribagh area is shifting to
Harindhara village of Hemayetpur Thana under Savar Upazilla over 200 acres land
and facilitated with central dumping yard, sludge power generating system (SPGS)
and Central Effluent Treatment Plant (CETP) for the purpose of eco-friendly
production from April 8, 2017.