Process for the purification of industrial waste-waters by nanofiltration

A process for purifying a waste-water stream of organic contaminants, comprising the steps of neutralization and biological treatment followed by an after-treatment which comprises:

• a. contacting a waste-water feedstream with at least one nanofiltration membrane, under pressure of about 5 to 80 Bar and a temperature of about 5.degree. to 95.degree. C., to form a permeated stream which has reduced organic carbon content relative to the feedstream, and recovering the permeated stream, said nanofiltration membrane being characterized by retention of organic substances with a molecular weight of about 500 Daltons or greater, and a retention coefficient for NaCl of about 0% and for Na.sub.2 SO.sub.4 of about 20%, and
• b. contacting the waste-water with an adsorption material selected from polystyrene and acrylic ester resins, metal oxides, ion exchangers, filtering earths, active carbon, and mixtures thereof, in an amount and for a time sufficient to reduce the organic carbon content of the waste-water, and recovering the treated waste water from the adsorption material.

A process for purifying a waste-water stream of organic contaminants, comprising the steps of neutralization, clarification, biological purification, and re-clarification, followed by an after-treatment which comprises:

• contacting a waste-water feedstream with at least one nanofiltration membrane, under pressure of about 5 to 80 Bar at a temperature of about 5.degree. to 95.degree. C., to form a permeated stream which has reduced organic carbon content relative to the feedstream, and recovering the permeated stream, said nanofiltration membrane being characterized by retention of organic substances with a molecular weight of about 500 Daltons or greater, and a retention coefficient for NaCl of about 0% and for Na.sub.2 SO.sub.4 of about 20%.