This paper summarizes recent technologies for wastewater treatment and recycling in the steel industry. At present, the main methods of water resource planning for the reduction of water consumption include the reuse of water multiple times, the recycling of wastewater, quality improvement of wastewater, and water use management. The present paper is primarily focused on two treatment technologies for the improvement of reclaimed water quality and for wastewater recycling and discharge: membrane bioreactor (MBR) and electrodialysis reversal (EDR). In a case study on MBR systems, after an 80% reduction in the chemical oxygen demand (COD) of wastewater post conventional activated sludge treatment, a 20% reduction in COD, from 277 mg/L, and a 95% reduction in suspended solids (S.S.), from 100 mg/L, could be achieved using an MBR system. This demonstrates the superior efficiency of MBR compared to conventional activated sludge systems. In another case study, a 96% reduction in COD, from 1,590 mg/L, and a 98% reduction in S.S., from 211 mg/L, in oily wastewater discharged by a cold rolling mill were achieved using an MBR. With respect to EDR systems, in one case study, a neutral pH value, an 80% reduction in conductivity, from 1,800 μS/cm, and a 90% reduction in chloride ions, from 280 mg/L, were achieved in low-pH cooling water. In another case study, a neutral pH value, an 85% reduction in conductivity, from 1,200 μS/cm, and an 89% reduction in chloride ions, from 180 mg/L, were achieved in low-pH EGL(Electrolytic Galvanizing Line, EGL) rinse wastewater after EDR treatment. Thus, EDR treatment accomplished the aim of wastewater recycling and reuse. In an era of water scarcity, the emergence of reclaimed water effectively compensates for water shortages. However, for further treatment and use of reclaimed water for the satisfaction of manufacturing needs, improvements in water quality regulations and water treatment technologies are required, so as to achieve a balance between raw water and reclaimed water.
Keywords: industrial water, water conservation, wastewater recycling and reuse, cooling water, reclaimed water