Treatment Of Heavy Metals (Cr And Cd) In Municipal Sewage Sludge By Using Electrokinetic Technology

Electrokinetic technology is a new potential technology which developed in recent decades, has been widely used for in situ remediation of soil and also used to remove heavy metals form sludge gradually. In this paper, the electrokinetic technique for removing heavy metals in sewage sludge was examined. And the chromium and cadmium were, respectively,taken as the target pollutant. The results are given as follows.In electrokinetic technique experiments of chromium contaminated sludge, the current great influence on the removal rate, when the current is 50mA, the average Cr (â…¥) removal rate was 76.07 %, and the total chromium removal rate was 62.35 %. In the study of the pH impact, the best method is to control the cathode solution pH with citric acid, in which Cr (â…¥) removal rate reached 92.72% of its cross section, and the total chromium removal efficiency reached 85.88%. This illustrated that the electrokinetic technology can effectively remove the chrome sludge. During the inspection of the effect of time on the removal rate, this paper respectively discussed the sludge cross Cr (â…¥) and total chromium removal rate after the restoration 4h, 5h, 6h. The results show that: when only adjusting the background-pH, the repair time had little effect on the removal rate; while controlling of the cathode solution pH, the repair time had significant effect on the removal rate. When using the acetate to control cathode pH, the removal rate of Cr(â…¥) and total Cr are 54.15% and 52.39% respectively after a 4h, which compare to 6h, the removal rate are 89.39% and 84.71%. In addition, citric acid is also studied, which is obviously better than acetate. Results show that the removal rate of Cr(â…¥) and total Cr are 76.21% and 69.19% respectively after a 4h, which compare to 6h, the removal rate are 99.76% and 90.49%.The infections of current, pH and remediation time on the removal rate are also studied in the sewage sludge repair experiment of Cadmium. Results reveal that enhancing the applied current can significantly increase the removal rate of Cadmium, and it can reach 65.30% when the current is 50mA. Similar conclusions are obtained about the impact of pH, in which the effect of different background-pH and cathode pH of variety acid reagents are investigated. Furthermore, using citric acid to control cathode pH is the best one, which can reach a high removal rate to 60.8%. Different removal time, 4h, 5h and 6h, are also studied in this part, and the removal rate can reach the highest level as 81.10%.