Water and Wastewater Minimization in Tannery by Using Water Pinch Technology Case Study (Ethio Leather Industry (ELICO) Glove and Hide Unit(Ethio Leather Industry (ELICO) Glove and Hide Unit
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Date
2011-07
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Addis Ababa University
Abstract
In tanneries, the phases of conditioning and preparing the hide/skin for tanning, as well as the
transportation and fixation of tanning substances are all carried out in aqueous media. Most
of the steps of these processes are carried out with fresh water. This leads to the generation of
high wastewater flowrates which will have to be treated due to the relatively high
concentrations of pollutants. The high effluent volume requires huge investments for effluent
treatment plants in order to meet the required specification for the discharge of liquid
effluents to various water bodies.
In this study the total water consumption reduction of the case study tannery is investigated
by using water reuse technique in some stages of the process. For the systematic design of
water reuse networks, the theory of the water pinch methodology is described, which are
proved to be effective in identifying water reuse opportunities. Experimental results on pilot
scale are shown that the methodology is demonstrated to be successful. Water reuse reduces
the load of the wastewater treatment plant as well as it reduces the costs.
During the analysis, it was tested that 100% of the effluent from de-liming discharge can be
reused for presoaking and main soaking stages, reuse in bating washing-1 100% and bating
washing-2 75% from bating washing-3, and the reuse of 80% of washing after shaving for
tanning float. The physical and chemical parameters analyzed in the processes and for the
products with reuse practice did not present any considerable difference when compared with
the conventional process. This demonstrates the viability of reuse practice in tanning
industry.
This study identified a potential scope of reducing both freshwater and wastewater by 44%. In turn the water reduction represents a total potential annual savings of 307200 Birr, taking
into account the raw water and wastewater treatment costs, labor cost, electrical and chemical
costs.
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Keywords
Wastewater, Water, Tannery, Water Pinch Technology, ELICO