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INTRODUCTION TO THE TREATMENT OF TANNERY EFFLUENTS every tanner What every tanner should know about effluent treatment U nited N ations I ndustrial D evelopment.

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Presentation on theme: "INTRODUCTION TO THE TREATMENT OF TANNERY EFFLUENTS every tanner What every tanner should know about effluent treatment U nited N ations I ndustrial D evelopment."— Presentation transcript:

1 INTRODUCTION TO THE TREATMENT OF TANNERY EFFLUENTS every tanner What every tanner should know about effluent treatment U nited N ations I ndustrial D evelopment O rganization Part I J. Buljan, I. Kral Compiled by J. 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 TANNERY Site LEATHER PROCESSING TANNERY Plant/Building(s) Finished leather CrustWet-blue Fresh air Water Chemicals Raw hides Solid waste Air pollution PRODUCTS Effluent for treatment Processing Disposal

4 Green fleshing BOD,COD, SS, TDS, organic N BOD,COD, SS, TDS, alkalinity, sulphides, organic N, ammonia N BOD,COD, SS, TDS, alkalinity, sulphides BOD,COD, TDS, ammonia N BOD,COD, SS, TDS, acidity, salts, chrome, vegetable tans, syntans Fleshings (fat containing organic matter) Hair, lime, organic matter containing sludge Lime fleshings (fat containing org. matter) Lime split and trimmings (limed organic matter) Chrome split (chrome containing org. matter) Shavings (chrome containing org. matter) H2SH2S NH 3 Unhairing Liming Lime fleshing Lime splitting Trimming Deliming Bating Degreasing (sheep/pigskins) Pickling Tanning Chrome splitting Soaking WATER pollutants SOLID pollutants AIR pollutants RAW HIDES LEGEND: BOD – Biochemical Oxygen Demand COD – Chemical Oxygen Demand TDS – Total Dissolved Solids SS – Suspended Solids BOD,COD, SS, TDS, acidity, salts, chrome, vegetable tans, syntans Sammying WET-BLUE Shaving

5 LEATHER BOD,COD, TDS, chrome tans, dyes, fats Reminder of finishing agents Chrome trimmings (chrome and prefinishing chemicals containing org. matter) Solvents, CH 2 O Drying Buffing Trimming Retanning, dyeing Fat liquoring Finishing WATER pollutants SOLID pollutants AIR pollutants CRUST LEGEND: BOD – Biochemical Oxygen Demand COD – Chemical Oxygen Demand TDS – Total Dissolved Solids SS – Suspended Solids WET-BLUE

6 LEATHER Green fleshing BOD,COD, SS, TDS, organic N BOD,COD, SS, TDS, alkalinity, sulphides, organic N, ammonia N BOD,COD, SS, TDS, alkalinity, sulphides BOD,COD, TDS, ammonia N BOD,COD, SS, TDS, acidity, salts, chrome, vegetable tans, syntans BOD,COD, TDS, chrome tans, dyes, fatsReminder of finishing agents Fleshings (fat containing organic matter) Hair, lime, organic matter containing sludge Lime fleshings (fat containing org. matter) Lime split and trimmings (limed organic matter) Chrome split (chrome containing org. matter) Shavings (chrome containing org. matter) Chrome trimmings (chrome and prefinishing chemicals containing org. matter) H2SH2S NH 3 Solvents, CH 2 O Unhairing Liming Lime fleshing Lime splitting Trimming Deliming Bating Degreasing (sheep/pigskins) Pickling Tanning Chrome splittingDrying Buffing Trimming Retanning, dyeing Fat liquoring Finishing Soaking WATER pollutants SOLID pollutants AIR pollutants RAW HIDES CRUST LEGEND: BOD – Biochemical Oxygen Demand COD – Chemical Oxygen Demand TDS – Total Dissolved Solids SS – Suspended Solids BOD,COD, SS, TDS, acidity, salts, chrome, vegetable tans, syntans Sammying WET-BLUE Shaving

7 Chemicals Added in process In/on leather & splits Wasted EXAMPLE OF MASS BALANCE OF CHEMICALS IN LEATHER PROCESSING kg/t of wet salted hide Chrome oxide (Cr 2 O 3 ) Organic tannins Fatliquors Dyestuffs 541 Acids, bases, salts 191- Tensides 3-3 Enzymes 5-5 Finishing products Total

8 ParameterUnit Biochemical oxygen demand (BOD 5 ) mg O 2 /l Chemical oxygen demand (COD) mg O 2 /l Suspended solids (SS) mg/l Trivalent chromium (Cr 3+ ) mg Cr/l Sulphides, S 2- mg S/l Total Kjeldahl Nitrogen (TKN) mg N/l Chlorides, (Cl - ) mg Cl/l Sulphates (SO 4 2- ) mg SO 4 /l Oil and grease mg/l Total Dissolved Solids (TDS)* mg/l pH TYPICAL TOTAL POLLUTION LOAD Conventional process, expressed as concentration in combined raw effluent * The main constituents of the TDS are chlorides (Cl - ) and sulphates (SO 4 2- ) listed earlier. Average total pollution load Typical limits, surface waters Locally specific

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 (SO 4 2- ) listed earlier. kg/day Parameter Biochemical oxygen demand (BOD 5 ) Chemical oxygen demand (COD) Suspended solids (SS) Trivalent chromium (Cr 3+ ) Sulphides, S 2- Total Kjeldahl Nitrogen (TKN) Chlorides, (Cl - ) Sulphates (SO 4 2- ) Oil and grease Total Dissolved Solids (TDS)* pH kg/t

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

11 EFFLUENT HANDLING WITHIN TANNERIES CROME RECOVERY PLANT (optional) SULPHIDE OXIDATION (optional) MnSO 4 (H 2 O) dosing Steam H 2 SO 4 Diatomaceous earth Cr- sludge Impurities Recovered Cr-liquor RECYCLED 20 mm10 mm LIMING EFFLUENT 20 mm10 mm TANNING LIQUOR POST-TANNING & OTHER EFFLUENT SOAKING EFFLUENT 20 mm10 mm 6 mm TO TANNERY EFFLUENT COLLECTION AND CONVEYANCE SYSTEM Grit and floating matter (grease and oil) chamber Septic tank (optional) SANITARY EFFLUENT Sludge drying beds (optional) TRANSPORT TO SLUDGE LANDFILL NaOH dosing

12 TANNERY SITE TYPICAL EFFLUENT TREATMENT SETUP VARIANT: CETP for a tannery cluster TANNERY Other tanneries CETP Common Effluent Treatment Plant PT Pre-treatment S S 2- oxidation Cr recovery River/channel Reservoir/lake/sea

13 TANNERY SITE TYPICAL EFFLUENT TREATMENT SETUP TANNERY Communal and other effluent MWWW Municipal Wastewater Works PT Pre-treatment PhCh Physical- Chemical treatment S S 2- oxidation Cr recovery River/channel Reservoir/lake/sea VARIANT: Final treatment together with urban wastewaters at the municipal plant


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