Apply EDTA and NTA to Extract Fe and Al Ions from Sewage Sludges: Batch Study

Heavy metals accumulating in the sludge after active sludge process limit the further use of sludge due to their toxicity. This study was carried out to extract Fe and Al from practical sewage sludge at different pH values and EDTA / NTA doses. The result showed that EDTA and NTA acted significant extraction on Fe and Al from sewage sludge when pH <7, and only a little effect after pH of 7. Fe and Al have similar tendency of being extracted, while Fe is more readily extracted than Al from practical sewage sludge. The most extraction percentage by EDTA reached up to 62.5% and 26.9% for Fe and Al at pH of 2.69, and that by NTA reached up to 36.3% and 26.9% for Fe and Al at pH of 4.57 and 2.78 respectively. Also, Fe and Al were effect by SS apparently when EDTA was applied, and Fe was more, however hardly when NTA. Comparing the NTA with EDTA treatment of sludge, Fe is more easily extracted by EDTA than NTA.