Two-stage membrane process (UF/NF) for treatment of water process in the steel industry at a pilot scale

Increasing industrial activities in developing countries caused water resources to be at risk and there is a need to manage the consumption of all kinds of water. Two of the most critical industries, which use water in vast amounts, are iron ore concentration plants and steel industries. Their effluents abound with ferrous compounds and most of the water is evaporated. In that case, these effluents should be treated. Among treatment methods, the membrane process showed great outputs and attracted much attention. In this research, a two-stage membrane process was designed to improve the water process of Neyriz Ghadir Steel Company (Iran) and reuse the cleaned water. The process included pre-treatment operation (sand filter, activated carbon, and cationic exchange resin), ultrafiltration (UF) and nanofiltration (NF) stages. UF membrane was prepared by phase separation of waste acrylic fibers as initial materials, while the NF membrane was prepared by interfacial polymerization of polyamide thin-film on the UF membrane. These membranes were converted to the spiral module. The properties of UF, and NF membranes were completely analyzed. During the two-stage membrane process, most of the water parameters such as total hardness (from 536 to 24 ppm), electrical conductivity (from 2470 to 224 μs/cm) and also, and the concentration of ferrous compounds (from 170 to 0 ppm) decreased. The fouling behavior of acrylic ultrafiltration and thin-film composite nanofiltration membranes was completely assessed, indicating low fouling and stable flux (133.68 LMH for UF and 21.68 LMH for NF).