Recycling of Wastewater from Raw Hide to Wet Blues in Leather Manufacture

Waste water generated from soaking to chrome tanning of leather manufacturing processes contains complicated components, which would cause serious impact on environment. Waste water recycling can effectively reduce the environmental problems produced by the tannery. In general condition, defects inevitablely existe when waste water is directly reused in the recycle. For example, soaking and deliming waste water can cause 'rough' grain. When waste limed water was directly applied, pelt' s swelling inhibition phenomenon would result in decrease of rendment of wet blue, and waste chrome water would make crust rougher and its color darker. The waste water direct application would reduce rendment of wet blue, of which waste limed water is the most serious. This paper has focused on the negative impact resulted by waste water directly applied and a series of solutions are provided as to achieve that rendment of wet blue increased 0.5-0.8%, shrinkage temperature raised 1.0-1.5 degrees C (compared to conventional process) with convenient handling and low investment. Meanwhile chemical cost can be saved by 7-12%, and effluent discharge can be reduced by 60-70%. Then the waste water recycling in soaking, liming, deliming-bating and pickling-chrome tanning can be achieved comprehensively.