Experimental Investigation On Wastewater Treatment For An Iron And Steel Plant By The Membrane Filtration Technique

The iron and steel corporation has been one of the important basic industries for the economic development of China, which has also been a significant contribution to the national economic development. However, it has been a water consumer with a large emission of wastewater; wastewater treatment of iron and steel industries has been paid more attention. To perform wastewater treatment and reclaimation using advanced technologies will benefits the producing cost; furthermore, it will be helpful to the protection of water resource.A combined membrane separation technique of continuous microfiltration(CMF) and reverse osmosis(RO) was employed to treat the effluents derived from a sequencing batch reactor(SBR) process, considering the waterwater treatment engineering of an iron and steel industry in Qinhuangdao. A measurement technique of chemical oxygen demand(COD) was established by the ultraviolet spectrophotometry. Removal investigations of fluoride anion were also performed using the techniques of active alumina adsorption and aluminium salt coagulation, because of the high concentration of fluoride. The conclusions based on this research are shown as follows:(1)Values of COD and ultraviolet absorbance(ABS) measure at 210 nm follow an empirical equation: COD = 0.00579 +(14.656±0.591)×ABS.(2)Results of the pilot-scale test of water treatment by the CMF-RO membrane system show that the CMF membrane can remove the suspended solids, bacteria and microorganisms efficiently. The values of slit density index(SDI), and turbidity are less than 3, and 0.5 NTU, consistent with the influent requirement of RO membrane system. The conductivity of RO effluent is smaller than 5μs/cm, furthermore, both removals of salt and COD are higher than 99%。(3)Effluent quality of the CMF-RO membrane system is as follows: color = 0, conductivity < 5 μs/cm, TOC < 3 mg/L, COD < 5 mg/L, which can meet the requirements of greening, flushing water, and industry cooling water, etc.(4)The removal of fluoride anion is the most optimal by the active alumina adsorption technique, as the value of p H was kept at 5 and the weight molar ratio of alumina and fluoride ranged from 6 to 8. The optimal parameters of fluoride removal by the aluminium salt coagulation process were ascertained. The p H value of the solution is in the range of 5.8~6.5, the weight molar ratio of aluminum sulfate and fluoride is in the range of 6~8. In this research, between the two techniques mentioned above, the aluminium salt coagulation is selected to remove fluoride, and then the combined method of aluminium salt coagulation and microfiltration filtration is proposed.