Application Of Membrane Technology In Treatment Of Wastewater From Iron And Steel Production

Iron and steel industry is a high pollution, high water consumption and resource-based industry. Its efflux of wastewater accounts for about8%of the total discharge of wastewater in China, and it is a large water consumption and wastewater discharge industry. It is an effective way to reduce water pollution by iron and steel industry, reduce water consumption per ton steel and production costs in this industry for decreasing the amount of fresh water used, mitigating the shortage of water resources and water pollution, achieving sustainable, benign development of industry.The water contains excessive salinity after treated with existing wastewater treatment process in iron and steel industry. This will affect the receiving water environment and water reuse.A combination of membrane technology was employed for reducing the salinity and improving the use value of treated-water in a iron and steel enterprise. The results showed that SDI value of the effluent treated with MBR membrane remained4-5or so; after coordination with the ultrafiltration membrane, SDI values could drop to2or less, and satisfactorily met water requirements for the reverse osmosis system. At a certain operating pressure, there is a corresponding maximum membrane flux and corresponding output frequency, the operation frequency of maximum flux for high pressure membrane pump lagged that for the low pressure membrane pump. The reverse osmosis system pressure increased from0.6MPa to1.0MPa, the maximum flux of membrane escalated from6.9L/(m2-h) up to16.6L/(m2-h), in the range of0.6MPa to0.8Mpa of reverse osmosis pressure, the film’s largest flux increased with a linear upward trend, fitting with the linear equation Y=35.5X-14.62(R=0.995); when reverse osmosis pressure varied from0.8MPa to1.0MPa, the maximum flux membrane increased with a linear trend up to a platform, in line with the linear equation Y=13X+3.77(R=0.976). Increase in operating pressure can improve desalting efficiency and the recovery rate, but too much pressure will reduce membrane life. This combination has a high desalting efficiency especially for Cl-and Na+with the desalting efficiency of more than95%, up to100%. The cost of the combined membrane technology may counteract the interest from the reuse of treated water. Therefore, the combined membrane technology has good environmental and social benefits.