Research and chemical operations. The conversion of outer coverings

Researchtopic: Acase study on characterization of solid waste & discharged effluents ofTannery Estate Dhaka (TED) IntroductionLeather,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 involvementof both mechanical and chemical operations. The conversion of outer coverings ofcarcasses which is a by-product of meat industry, into leather practiced by theprimitive people from ancient time has become one of the most prime-concerned globalindustries in world economy.

The leather industry, well known as user ofnatural resources is always not only given priority for its economic dominancebut also for environmental influence as it generates pollutant wastes havinghazardous impact on environmental degradation.. These wastes are largelygenerated during leather processing and effluent discharge. For this withoutproper control of disposal of wastes, the leather industry is now regarded ashighly potential polluter industry.

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In the conversion of 1 ton wetsalted hides, 500 kg of different chemicals, 40  of water (process and technical water) and2600-11700 kWh energy is consumed but only 200-250 kg of finished leather (grainand embossed split) is achieved containing only 72 kg chemicals inside which isonly 25.5% of the total used raw materials and discharge approximate 600 kg ofwaste in different forms. The wastes generated by the tanning industries are classified intothree groups such as liquid, solid and gaseous in nature and are enlisted inthe figure I.Figure:Types of wastes generated from tanneries during leather processingThe tanneriesgenerate around 6 million tons of solid waste as trimmings (both tanned and un-tanned),fleshing,splitting, shaving & buffing dust and sludge (both chrome contained andnon-chrome) atan average of 80% in leather processing per annum. During beam house and post tanningoperation, most of the solid wastes (trimmings, fleshing, splits and shavingdust) are generated, containing small amount ( 2-6% (w/w)) non-chrome mineralsubstance and influenced by quality of hides/skins, tanning technique andcondition process in characteristics. Moreover, useless splits, shaving dustand 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 plantgenerally bears water (up to 65% (w/w)), organic materials (30% (w/w)) andchromium (iii) compounds (approximately 2.5% (w/w)).

These solidwastes are might of limited implementation but possess serious environmental problemwithout safe disposal and treatment. Thoughcountries in the west are now shifting away from this industry, leather processingis still an unavoidable source of earning foreign money and export trade formany developing and under-developed countries. In Bangladesh, the leather industryis relatively an older industry with an age-old tradition of over seven decadeshas significant involvement of producing such leather, recognized for itssuperior grain pattern and strong fiber strength worldwide since 1940.According to the annual report of Bangladesh Economic Review of 2017, leather sectoris ranked third in terms of earning foreign money and around 1234 million$ achievedfrom this sector in fiscal year 2016-17. To keep this momentum steady, theleather industries situated in the capital’s Hazaribagh area is shifting toHarindhara village of Hemayetpur Thana under Savar Upazilla over 200 acres landand facilitated with central dumping yard, sludge power generating system (SPGS)and Central Effluent Treatment Plant (CETP) for the purpose of eco-friendlyproduction from April 8, 2017.