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Treatment of Effluent coming from Leather Finishing Industries

The objective of this project is to develop a treatment system for effluents from leather finishing industries, using membrane technologies which allow the recycling of water obtained through the same industrial process, and managing to reduce simultaneously the consumption of water (estimated at about 17 m³ per ton of leather) and the discharge of sewage.

The effluents from leather finishing industries are characterised by their limited reproducibility due to the high number and diversity of reagents used in the process and the large variety of manufactured products. However, the characterisation tests of these effluents show that all of them have common characteristics: a high organic load, suspended solids, conductivity, chrome, calcium and oils and fats.

The implementation of a treatment system for these effluents using membrane technologies implies a reduction in the pollutant load of the effluent to the levels required for reverse osmosis membranes in order to avoid their silting or degradation. For this reason, a study has been made of adequate pre-treatments to adapt the initial effluent to these demands. The pre-treatments which were studied are physical-chemical/activated carbon pre-treatment and micro/ultrafiltration pre-treatment.

The continuous tests carried out in industry using the pilot plant showed that the physical-chemical pre-treatment followed by absorption using active carbon and subsequently the reverse osmosis system (Ph/Ch+AC+RO) seems to be suitable for the treatment of effluent from leather finishing industries. It was observed that the operating conditions (pressure and flow) were kept constant and a final effluent was produced that was of a high enough quality that it could be recycled into the industrial process.

By using the proposed treatment, it seems possible to gain a recycling of 75% of the discharge volume from the industrial process. In the same way, the quality of recovered water is suitable to be reused in the industrial process without any noticeable difference being noticed in the leather that is processed using this recovered water.

Finally, it can be concluded that the implementation of this treatment system with a recycling of 75% of the effluent means an 18% saving on the cost of this (1.85 ?/m3) with respect to the physical-chemical treatment cost of the effluent that is necessary to adapt the discharge to environmental legislation (2.25 ?/m3).

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Record Number: 23316 / Last updated on: 1999-11-08
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