03528cas|a2200385 i 4500 20260818180012.0 230399s1994 th uzm rtt 00| a1eng d .b10556953 AIT Thesis no.EV-94-06 Chen, Hsin-jung Removal of heavy metals from digested sewage sludge by biological method Bangkok : Asian Institute of Technology, 1994 93 leaves Thesis ; no. EV-94-06 A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources & development Thesis (M.Eng.) - Asian Institute of Technology The presence of high concentration of heavy metals in digested sewage sludge strictly limits its possible application to agriculture lands. In order to render the sludge suitable for application to agricultural land and to prevent the environment from contamination, heavy metal concentration should be reduced to an acceptable level. A biological oxidation process called bacterial leaching was used to remove heavy metals from anaerobically digested sewage sludge. According to this study, T. ferrooxidans was found to play a significant role in heavy metal removal. The ferric iron could directly oxidized the metal sulfide to metal sulfate (indirect process) without bacteria participation; and this not only enhances the metal · leaching rate but also increases the metal removal efficiency. The ferrous iron, se1ved as an energy source for bacteria growth, significantly affected the heavy metal removal rate and removal efficiency. The metal removal rate and efficiency increased as ferrous iron concentration increased. However, the bacteria activity was surpressed when pH is high than 4.5. In addition, the orders of heavy metal removal efficiency was found being related to the solubility product of mineral sulfide. Sludge with high solids concentration may interference the mass transfer of 0 2 and C02; and this leads to lower the metal removal efficiency. The biological heavy metal removal efficiency from anaerobically digested sludge at pH 2. 5 and 30°C was observed as follows: copper, 80.71%, zinc, 91.61%, manganese, 92.44%, nickel 95.0%, chromium, 33.09%, and cadmium 41.67%. According to Flynn guidelines, the sludge used in this study was originally not acceptable for agricultural land application because of high zinc contents. It was decontaminated after bacterial leaching. Sewage Purification Heavy metals removal Umita, Teruyuki, Chairperson Chongrak Polprasert, Examination Committee Lee, Seong-Key, Examination Committee Government of Republic of China, Scholarship Donor Asian Institute of Technology. Thesis ; no. EV-94-06 Full-Text http://203.159.5.9/ait-thesis/detail.php?q=B15854 .b10556953 mnait x 240409 2 951012 m a x 0 mnait mnarc 22 40 Barcode : 30050120124259 CREATED : 2014-03-28 RECORD # : i1278185x LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 Barcode : 30050160055561 CREATED : 2016-11-05 RECORD # : i12975345 LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 99471 99471 0 0 0 0 MAIN MAIN mnait 2026-08-18 50.00 0 AIT Thesis no.EV-94-06 30050120124259 2026-08-18 18:00:12 3 2026-08-18 22 0 0 0 0 MAIN MAIN mnarc 2026-08-18 0 AIT Thesis no.EV-94-06 30050160055561 2026-08-18 18:00:12 2026-08-18 40