Oxide - One Of The Ferric Salt Coagulation Treatment Of Alkaline Arsenic Wastewater

The treatment of alkali wastewater including arsenic is the fatal environmental problem in the smelt of coloured metals. Ln this study, a new technology named as oxidation-coalgulation is developed to slove the problems of high pH and arsenic existed in wastewater from a metallurgic plant. The experiments conditions and mechanism of this technology are investigated. The results have shown that the technology can effectively remove arsenic from the wastewater. The effluence can satisfy the integrated wastewater discharge standard(GB 8978-1996).The coalgulation precipitation results show that when FeSO4, Fe2(SO<()3 and PFS are used as coagulation reagents, the removal rate of antimony could achieve 80-85% and the removal rate of arsenic is 50-70%. The optimum conditions of reagents: FeS04=2000mg/L, pH 5-6.5; Fe^SO^lSOOmg/L. pH4~6; PFS=2200mg/L, pH6~9. According to removal efficiency and treatment cost, PFS is the best reagent. The proper dose of PAM can improve the performance of sludge settlement and quality of effluence.In the process of oxidation-coalgulation experiments, the coalgulation step is invary and three kinds of oxidants are used: HaO:, NaCIO, aeration. The optimum oxidation conditions could be obtained through orthogonal test and single-factor test. The optimum conditions of oxidation: H2O2=800mg/L, pH<7, 10min; NaCIO =1400mg/L, pH7~10,20min; aeration =0.2m3/(h ?L), pH7~9.5, 100min. Comparing these three oxidation methods, we choose NaCIO as the best oxidant.After NaCIO oxidation, the coagulation experiment of PFS has proved that two stage coagulation could reduce PFS dose and output of sludge. In the first stage coagulation, PFS dose is 1300mg/L and PAM dose is 2mg/L. In second stage coagulation, PFS dose is 300mg/L and PAM dose is Img/L. After the wastewater is treated through oxidation and cougulation, the content of pollutants in the effluence can satisfy the standard of discharge.The mechanisms of oxditation-coalgultion technology involve oxidation, adsorption and coagulation.inOur test results have been adopted by Guangxi Hechi Nonferrous Metals Co. Led, and is going to put into use in this year. This technology not only slove the problem of environment that restrict the development of the corporation, but also offer a effective method to treat the similar wastewater.