Leather/Skin/Hide Processing Industry - Environmental Clearance

Leather / Skin / Hide Processing Industry (Tannery)surface water. Ground water from their own open wells/tubewells existing within theirpremises is also used by some tanneries. Most of the traditional tanneries store water inopen cement lined pits and ground level tanks. Water from these storage tanks would bepumped directly to the process zones.B. Wastewater generation and characteristicsVolume of wastewater (effluent) and its characteristics vary from tannery to tannery.They may also vary within the same tannery from time to time. The wastewater frombeam house process viz. soaking, liming, deliming, etc., are highly alkaline, containingdecomposing organic matter, hair, lime, sulphide and organic nitrogen with high BODand COD. The wastewater from tanyard process viz. pickling, chrome tanning are acidicand coloured. Effluent from vegetable tanning contains high organic matter. The chrometanning wastes contain high amounts of chromium mostly in the trivalent form. Thecharacteristics of combined wastewater before treatment and after treatment are given inTable 3.1.Table 3-1: Characteristics of WastewaterSLNo.ParametersAverage concentration inmg/litre (BeforeTreatment)Average concentrationin mg/litre(After Pretreatment)1. BOD 1850 7002. COD 4500 30003. Chloride 5500 12004. SS 3750 15005. Total Cr 165 38Source: Minimal National Standard for Tanneries: COINDS/35/1991-92,CPCB, DelhiThe pollution load per tonne of hides and skins process is given in Table 3-2Table 3-2: Pollution Load per tonne of Hides/Skins ProcessedS.No. Pollution Parameter Pollution Load (kg)1 Volume (m 3 ) 402 BOD 703 COD 1804 Chlorides (Cl) 2705 Dissolved Solids 6006 Suspended Solids (SS) 1007 Sulphides (S) 48 Chromium (Cr) 30Note: Composite Wastewater (no Segregation)Source: Central Leather Research InstituteTGM for Tanneries August 20103-8