New technologies and process for rational use of water in medium-size tanning enterprises

Kurzfassung

A southern Italian tanning company is looking for new low-cost technical solutions for the treatment of its plant wastewater. At present the company is equipped with a biological treatment system that should be improved in order to allow re-use of wastewater in the processing-stream. Both industries and research organisations are sought for technical cooperation and/or manufacturing agreements.

Details

An Italian tanning company carries out its activities going through the followings steps:
• Tanning on wet-blue leather.
• Black-dyeing.
• Finishing process.

The processing-stream (tanning and dyeing) utilises on average 50 litre/kg of processed leather.
The wastewater, discharged in sewer or in body surface waters, presents chemical features complying with the following limits set by the national law:

- Sewer:
* BOD5 < 250 mg/litre.
* COD <500 mg/litre.
* Total Chrome <4 mg/litre.
* Chrome VI <0,20 mg/litre.
* Sulphide <2 mg/litre.
* Sulphate <1000 mg/litre.
* Chloride <1200 mg/litre.
* Surfactants <4 mg/litre.
* Ammonia nitrogen <30 mg/litre.

- Body surface waters:
* BOD5 < 40 mg/litre.
* COD <160 mg/litre.
* Total Chrome <2 mg/litre.
* Chrome VI <0,20 mg/litre.
* Sulphide <1 mg/litre.
* Sulphate <1000 mg/litre.
* Chloride <1200 mg/litre.
* Surfactants <2 mg/litre.
* Ammonia nitrogen <15 mg/litre.

At present, the company is equipped with a biological wastewater treatment plant, but the water coming out is not recovered. Wastewater is considered as a sunk cost, hardly re-utilisable due to the risk of impairing the system operation.
The company is looking for new low-cost systems easily integrable in the existing plant, ensuring a rational recovery of water for the tanning processing stream.
The solutions proposed should limit the production of further residuals hardly disposable through the pre-existing treatment system.

Technical Specifications / Specific technical requirements:
The main requirements to be met are:
- Easy integrability into the pre-existing plant.
- Low economic impact.
- Recovery of water in order to re-use it in the tanning and dyeing activities.
- Limited production of further residues hardly disposable or re-utilisable in the tanning process (e. g.: concentrate production resulting from filtration technology).
- Easy management and maintenance.
- Durability.