| Author | Chen, Hsin-jung |
| Call Number | AIT Thesis no.EV-94-06 |
| Subject(s) | Sewage--Purification--Heavy metals removal
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources & development |
| Publisher | Asian Institute of Technology |
| Abstract | 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. |
| Year | 1994 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Umita, Teruyuki
|
| Examination Committee(s) | Chongrak Polprnsert ;Lee, Seong-Key
|
| Scholarship Donor(s) | Government of Republic of China |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1994 |