Division 5
United Kingdom
In order to reduce the pollutant load in the waste water before effluent treatment arising from the beamhouse process steps, BAT is to use an appropriate combination of the techniques given below.
| Technique | Description | Applicability | |
|---|---|---|---|
| a | The use of short floats | Short floats are reduced amounts of process water. When less water is present, the quantity of process chemicals which are discarded unreacted, is reduced. | The technique cannot be applied for the processing of calfskins. Applicability is also limited to:
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| b | The use of clean hides or skins | Use of hides or skins which have less manure adhering to the exterior, possibly through a formal ‘clean hides scheme’. | Applicable subject to the constraints of the availability of clean hides. |
| c | Processing fresh hides or skins | Unsalted hides or skins are used. Rapid post-mortem cooling combined with either short delivery times or temperature-controlled transport and storage are used to prevent their deterioration. | Applicability is limited by the availability of fresh hides or skins. Cannot be applied when a supply chain longer than two days is involved. |
| d | Shaking off loose salt from hides by mechanical means | Salted hides are opened out for processing in a manner which shakes or tumbles them, so that loose salt crystals fall off and are not taken into the soaking process. | Applicability is limited to tanneries processing salted hides. |
| e | Hair-save unhairing | Unhairing is carried out by dissolving the hair root rather than the whole hair. The remaining hair is filtered out of the effluent. The concentration of hair breakdown products in the effluent is reduced. | The technique is not applicable where facilities for the processing of hair for use are not available within a reasonable transport distance or when the hair use is not possible. Applicability is also limited to:
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| f | Using organic sulphur compounds or enzymes in the unhairing of bovine hides | The amount of inorganic sulphide used in unhairing is reduced by partially replacing it by organic sulphur compounds or by additional use of appropriate enzymes. | Additional use of enzymes is not applicable to tanneries producing leather with a visible grain (e.g. aniline leather). |
| g | Reduced ammonium use during deliming | The use of ammonium compounds in deliming is partially or completely replaced by the injection of carbon dioxide gas and/or the use of other substitute deliming agents. | The complete replacement of ammonium compounds by CO2 during deliming cannot be applied to the processing of materials whose thickness is over 1,5 mm. The applicability of partial or complete replacement of ammonium compounds by CO2 during deliming is also limited to:
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