Treatment of a chemical industry effluent by nanofiltration and reverse osmosis

Advanced filtration processes, namely nanofiltration (NF) and reverse osmosis (RO), can produce high-quality permeate from industrial effluents for a safe discharge or water reuse. In the present study, a biologically treated complex chemical industry wastewater was dead-end filtered through commercial NF and RO membranes. Dow Filmtec NF270, NF90, BW30 and SW30 membranes and Lewabrane RO B090 membrane were tested either separately or sequentially by NF followed by RO. Filtration through NF270 decreased chemical oxygen demand, color and conductivity from 202 mg/L, 222 Pt-Co and 10,150 μS/cm to 110 mg/L, 46 Pt-Co and 5,700 μS/cm, respectively. NF membrane mainly removed organic matter and divalent ions. RO membrane BW30 further removed these parameters as well as monovalent ions and thereby significantly decreased conductivity to 1,914 μS/cm. A secondary BW30 further decreased conductivity to 582 μS/cm for water reuse in industry. NF membranes served as pretreatment for RO membranes preventing fouling. Satisfactory membrane permeabilities were obtained as 2.2 LMH/bar for NF270 at 70% water recovery and 1.2 LMH/bar for the succeeding BW30 at 50% recovery at 15 bar filtration pressure. The study showed that sequential NF–RO process can successfully produce reusable permeates from a biologically pretreated chemical industry effluent.