Abstract

Waste water treatment plant running costs are regularly increasing. Economically speaking, it is more and more difficult to solve the problem of effluents containing toxic material combined with a major organic pollution load. Thus it is necessary to try to solve the problem through selective treatments of the heavily polluted floats before mixing.

In the case of leather manufacture, membrane technologies are interesting alternatives in comparison with the more classical physico-chemical and biological purification processes.

According to the size of the organic or inorganic complexes to be separated, ultrafiltration is well adapted to the recovery of suiphide in the liming float. Nanofiltration was tested for the recovery of trivalent chromium in the residual tanning floats. The great advantage of this technology is that it can be run without using any chemical, and no modification occurs with the residual chromium that can be reused after being concentrated.

After laboratory tests, some industrial experiments were run, using seven square metre pilot equipment in a French tannery.

The technical and economical interest of this technology will be discussed. It could be widely used in the next decade.