Advanced treatment of industrial wastewater by membrane filtration and ozonization Original Research Article

The present paper deals with nanofiltration (NF), ultrafiltration (UF) and ozonization pilot scale tests for revamping and improvement of an industrial plant that treats wastewaters coming from a wide range of hazardous industrial processes. Tests demonstrated that the best treatment is NF whose feed stream comes from sand filters rather than first ozonization stage before final discharge of the effluent. NF rejection coefficients resulted to be 31% for TDS, 94% COD, 9% Cl–, 47% surfactants, 66% phenols and 91% SO42–. UF was tested as NF pre-treatment but results were not so promising in terms of rejection and permeate flux, as well as fouling reduction. Other experimental tests were carried out in order to understand where to recycle the NF retentate: the best treatment in terms of COD reduction and biodegradability was ozonization followed by recycling to the physico-chemical stage. In the same manner, it was found that ozonization of the NF permeate is the best process solution before final treatment and discharge of the effluent.