WASTE MANAGEMENT IN LEATHER INDUSTRY

57 44Hair shaving methodsRecycling LimingLiquorRecycling of un- hairingliquorsLime Splitting andtrimmingApplication of weakacids in delimingprocessclose to neutral, which can then easily be processed torecover fats and proteins with good marketing possibilitiesand to save liming and unhairing chemicals. Further greenfleshing also improves the penetration of the chemicals andhence improves the quality of finished leather.Hair saving system use smaller quantities of sulfide ascompared to hair destructionsystem, and allows easy separation of the protein constitutedby the undissolved hair and hence imply less pollution thanthe hair dissolving process. The procedure results in asignificant reduction of COD, BOD5 , nitrogen, sulfide, totaland suspended solids in the wastewater, besides a decreaseof sulfide consumption. The hair saving would decrease theorganic load for treatment plant.Some of the liming unhairing techniques permit a directreuse of the spent liquors afterdecantation and/or filtration. The procedure permits savingsof water, sulfide, and lime.By reuse of un-hairing liquors after separation of insolublesubstances by sedimentation important savings are claimedincluding 50 % sulphide, 40% lime and 60% of processwaterSplitting and trimming is usually carried out after tanningwhich results in a by-product of low quality containingchromium in it. If these operations are carried out with thepelt, the produced by-product can be sold easily in themarket than those resulting from splitting and trimming ofwet blue (tanned hides/skins). The un-tanned solid wastewill be a good raw material for manufacturing of gelatin oranimal feed. This will also results in a reduction in thequantities of chemicals used for deliming, pickling, tanningand consequently the load of the pollutants in wastewaterwill be considerably reduced.Application of weak acids (organic) can eliminate thedischarge of ammonium salt from deliming process