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INTRODUCTION TO T HE T REATMENT OF TANNERY EFFLUENTS

INTRODUCTION TO T HE T REATMENT OF TANNERY EFFLUENTS. What every tanner should know about effluent treatment. U nited N ations I ndustrial D evelopment O rganization. Part I. Compiled by J . Buljan , I. Kral. 1. Load, norms, in-house treatment. Pollution load Discharge norms

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INTRODUCTION TO T HE T REATMENT OF TANNERY EFFLUENTS

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  1. INTRODUCTIONTOTHE TREATMENTOF TANNERY EFFLUENTS What every tanner should knowabout effluent treatment United NationsIndustrialDevelopmentOrganization Part I Compiled byJ. Buljan, I. Kral

  2. 1. Load, norms,in-house treatment • Pollution load • Discharge norms • General overview of treatment of tannery effluents • Segregation of streams • Treatment of spent liming floats • Treatment of chrome-bearing floats • Linking of individual tanneries to a CETP or MWWW

  3. Processing Disposal TANNERY Site Raw hides PRODUCTS TANNERY Plant/Building(s) LEATHER PROCESSING Wet-blue Chemicals Crust Effluent for treatment Water Air pollution Fresh air Finished leather Solid waste

  4. WATER pollutants RAW HIDES SOLID pollutants AIR pollutants Soaking BOD,COD, SS, TDS, organic N Fleshings (fat containing organic matter) Green fleshing Hair, lime, organic matter containing sludge BOD,COD, SS, TDS, alkalinity, sulphides, organic N, ammonia N Unhairing Liming H2S Lime fleshing BOD,COD, SS, TDS, alkalinity, sulphides Lime fleshings (fat containing org. matter) Lime splitting Trimming Lime split and trimmings (limed organic matter) NH3 Deliming Bating BOD,COD, TDS, ammonia N Degreasing (sheep/pigskins) BOD,COD, TDS, ammonia N BOD,COD, SS, TDS, acidity, salts, chrome, vegetable tans, syntans BOD,COD, SS, TDS, acidity, salts, chrome, vegetable tans, syntans Sammying Pickling Tanning Chrome split (chrome containing org. matter) Chrome splitting Shaving Shavings (chrome containing org. matter) WET-BLUE LEGEND: BOD – Biochemical Oxygen Demand COD – Chemical Oxygen Demand TDS – Total Dissolved Solids SS – Suspended Solids

  5. WATER pollutants SOLID pollutants AIR pollutants WET-BLUE Retanning, dyeing Fat liquoring BOD,COD, TDS, chrome tans, dyes, fats Drying Chrome trimmings (chrome and prefinishing chemicals containing org. matter) Buffing Trimming CRUST LEGEND: BOD – Biochemical Oxygen Demand COD – Chemical Oxygen Demand TDS – Total Dissolved Solids SS – Suspended Solids Solvents, CH2O Reminder of finishing agents Finishing LEATHER

  6. WATER pollutants SOLID pollutants AIR pollutants RAW HIDES BOD,COD, SS, TDS, organic N Soaking Fleshings (fat containing organic matter) Green fleshing Hair, lime, organic matter containing sludge Unhairing Liming BOD,COD, SS, TDS, alkalinity, sulphides, organic N, ammonia N H2S Lime fleshing BOD,COD, SS, TDS, alkalinity, sulphides Lime fleshings (fat containing org. matter) Lime splitting Trimming Lime split and trimmings (limed organic matter) NH3 Deliming Bating BOD,COD, TDS, ammonia N Degreasing (sheep/pigskins) BOD,COD, TDS, ammonia N Pickling Tanning BOD,COD, SS, TDS, acidity, salts, chrome, vegetable tans, syntans BOD,COD, SS, TDS, acidity, salts, chrome, vegetable tans, syntans Sammying Chrome split (chrome containing org. matter) Chrome splitting Shaving Shavings (chrome containing org. matter) WET-BLUE Retanning, dyeing Fat liquoring BOD,COD, TDS, chrome tans, dyes, fats Drying LEGEND: BOD – Biochemical Oxygen Demand COD – Chemical Oxygen Demand TDS – Total Dissolved Solids SS – Suspended Solids Chrome trimmings (chrome and prefinishing chemicals containing org. matter) Buffing Trimming CRUST Solvents, CH2O Reminder of finishing agents Finishing LEATHER

  7. EXAMPLE OF MASS BALANCE OF CHEMICALSIN LEATHER PROCESSING kg/t of wet salted hide

  8. TYPICAL TOTAL POLLUTION LOAD Conventional process, expressed as concentration in combined raw effluent *The main constituents of the TDS are chlorides (Cl-) and sulphates (SO42-) listed earlier.

  9. TYPICAL TOTAL POLLUTION LOAD Conventional process, kg/t of wet salted hide Tannery with 5 t/day wet-salted input *The main constituents of the TDS are chlorides (Cl-) and sulphates (SO42-) listed earlier.

  10. IN-HOUSE SEGREGATION OF STREAMSLinked to a CETP To the treat- ment plant Screens SULPHIDE OXIDATION UNIT Grit floating matter chamber Septic tank (optional) Screens Screens CR-RECOVERY UNIT Liming effluent Soaking and other effluent Post-tanning effluent Tanning liquor S h o w e r s, t o i l e t s Sanitary effluent Recovered Cr-liquor TANNERY

  11. EFFLUENT HANDLING WITHIN TANNERIES SOAKING EFFLUENT LIMING EFFLUENT TRANSPORT TO SLUDGE LANDFILL 20 mm 10 mm SULPHIDE OXIDATION (optional) MnSO4(H2O)dosing Sludge drying beds (optional) Steam CROME RECOVERY PLANT (optional) 20 mm 10 mm TANNING LIQUOR 20 mm 10 mm NaOH dosing Recovered Cr-liquor RECYCLED Diatomaceous earth Grit and floating matter (grease and oil) chamber H2SO4 Cr-sludge 6 mm Impurities POST-TANNING & OTHER EFFLUENT TO TANNERY EFFLUENT COLLECTION AND CONVEYANCE SYSTEM SANITARY EFFLUENT Septic tank (optional)

  12. TYPICAL EFFLUENT TREATMENT SETUP TANNERY SITE River/channel CETP TANNERY PT Common Effluent Treatment Plant VARIANT:CETP for a tannery cluster Pre-treatment Cr S Cr recovery S2- oxidation Other tanneries Reservoir/lake/sea

  13. TYPICAL EFFLUENT TREATMENT SETUP VARIANT:Final treatment together with urban wastewaters at the municipal plant Communal and other effluent MWWW Municipal Wastewater Works PhCh River/channel Physical- Chemical treatment TANNERY SITE PT TANNERY Pre-treatment Cr S Cr recovery S2- oxidation Reservoir/lake/sea

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